A glycine-rich, heat-labile serum glycoprotein that contains a component of the C3 CONVERTASE ALTERNATE PATHWAY (C3bBb). Bb, a serine protease, is generated when factor B is cleaved by COMPLEMENT FACTOR D into Ba and Bb.
A component of the CLASSICAL COMPLEMENT PATHWAY. C2 is cleaved by activated COMPLEMENT C1S into COMPLEMENT C2B and COMPLEMENT C2A. C2a, the COOH-terminal fragment containing a SERINE PROTEASE, combines with COMPLEMENT C4B to form C4b2a (CLASSICAL PATHWAY C3 CONVERTASE) and subsequent C4b2a3b (CLASSICAL PATHWAY C5 CONVERTASE).
An important soluble regulator of the alternative pathway of complement activation (COMPLEMENT ACTIVATION PATHWAY, ALTERNATIVE). It is a 139-kDa glycoprotein expressed by the liver and secreted into the blood. It binds to COMPLEMENT C3B and makes iC3b (inactivated complement 3b) susceptible to cleavage by COMPLEMENT FACTOR I. Complement factor H also inhibits the association of C3b with COMPLEMENT FACTOR B to form the C3bB proenzyme, and promotes the dissociation of Bb from the C3bBb complex (COMPLEMENT C3 CONVERTASE, ALTERNATIVE PATHWAY).
A serum protein which is important in the ALTERNATIVE COMPLEMENT ACTIVATION PATHWAY. This enzyme cleaves the COMPLEMENT C3B-bound COMPLEMENT FACTOR B to form C3bBb which is ALTERNATIVE PATHWAY C3 CONVERTASE.
The larger fragment generated from the cleavage of COMPLEMENT C3 by C3 CONVERTASE. It is a constituent of the ALTERNATIVE PATHWAY C3 CONVERTASE (C3bBb), and COMPLEMENT C5 CONVERTASES in both the classical (C4b2a3b) and the alternative (C3bBb3b) pathway. C3b participates in IMMUNE ADHERENCE REACTION and enhances PHAGOCYTOSIS. It can be inactivated (iC3b) or cleaved by various proteases to yield fragments such as COMPLEMENT C3C; COMPLEMENT C3D; C3e; C3f; and C3g.
A serine protease that is the complex of COMPLEMENT C3B and COMPLEMENT FACTOR BB. It cleaves multiple COMPLEMENT C3 into COMPLEMENT C3A (anaphylatoxin) and COMPLEMENT C3B in the ALTERNATIVE COMPLEMENT ACTIVATION PATHWAY.
A glycoprotein that is central in both the classical and the alternative pathway of COMPLEMENT ACTIVATION. C3 can be cleaved into COMPLEMENT C3A and COMPLEMENT C3B, spontaneously at low level or by C3 CONVERTASE at high level. The smaller fragment C3a is an ANAPHYLATOXIN and mediator of local inflammatory process. The larger fragment C3b binds with C3 convertase to form C5 convertase.
Complement activation initiated by the interaction of microbial ANTIGENS with COMPLEMENT C3B. When COMPLEMENT FACTOR B binds to the membrane-bound C3b, COMPLEMENT FACTOR D cleaves it to form alternative C3 CONVERTASE (C3BBB) which, stabilized by COMPLEMENT FACTOR P, is able to cleave multiple COMPLEMENT C3 to form alternative C5 CONVERTASE (C3BBB3B) leading to cleavage of COMPLEMENT C5 and the assembly of COMPLEMENT MEMBRANE ATTACK COMPLEX.
The sequential activation of serum COMPLEMENT PROTEINS to create the COMPLEMENT MEMBRANE ATTACK COMPLEX. Factors initiating complement activation include ANTIGEN-ANTIBODY COMPLEXES, microbial ANTIGENS, or cell surface POLYSACCHARIDES.
A plasma serine proteinase that cleaves the alpha-chains of C3b and C4b in the presence of the cofactors COMPLEMENT FACTOR H and C4-binding protein, respectively. It is a 66-kDa glycoprotein that converts C3b to inactivated C3b (iC3b) followed by the release of two fragments, C3c (150-kDa) and C3dg (41-kDa). It was formerly called KAF, C3bINF, or enzyme 3b inactivator.
Degenerative changes in the RETINA usually of older adults which results in a loss of vision in the center of the visual field (the MACULA LUTEA) because of damage to the retina. It occurs in dry and wet forms.
Venoms from snakes of the genus Naja (family Elapidae). They contain many specific proteins that have cytotoxic, hemolytic, neurotoxic, and other properties. Like other elapid venoms, they are rich in enzymes. They include cobramines and cobralysins.
Serum glycoproteins participating in the host defense mechanism of COMPLEMENT ACTIVATION that creates the COMPLEMENT MEMBRANE ATTACK COMPLEX. Included are glycoproteins in the various pathways of complement activation (CLASSICAL COMPLEMENT PATHWAY; ALTERNATIVE COMPLEMENT PATHWAY; and LECTIN COMPLEMENT PATHWAY).
A glycoprotein that is important in the activation of CLASSICAL COMPLEMENT PATHWAY. C4 is cleaved by the activated COMPLEMENT C1S into COMPLEMENT C4A and COMPLEMENT C4B.
Endogenous proteins that inhibit or inactivate COMPLEMENT C3B. They include COMPLEMENT FACTOR H and COMPLEMENT FACTOR I (C3b/C4b inactivator). They cleave or promote the cleavage of C3b into inactive fragments, and thus are important in the down-regulation of COMPLEMENT ACTIVATION and its cytolytic sequence.
C5 plays a central role in both the classical and the alternative pathway of COMPLEMENT ACTIVATION. C5 is cleaved by C5 CONVERTASE into COMPLEMENT C5A and COMPLEMENT C5B. The smaller fragment C5a is an ANAPHYLATOXIN and mediator of inflammatory process. The major fragment C5b binds to the membrane initiating the spontaneous assembly of the late complement components, C5-C9, into the MEMBRANE ATTACK COMPLEX.
Physiologically inactive substances that can be converted to active enzymes.
The minor fragment formed when C5 convertase cleaves C5 into C5a and COMPLEMENT C5B. C5a is a 74-amino-acid glycopeptide with a carboxy-terminal ARGININE that is crucial for its spasmogenic activity. Of all the complement-derived anaphylatoxins, C5a is the most potent in mediating immediate hypersensitivity (HYPERSENSITIVITY, IMMEDIATE), smooth MUSCLE CONTRACTION; HISTAMINE RELEASE; and migration of LEUKOCYTES to site of INFLAMMATION.
A subcomponent of complement C1, composed of six copies of three polypeptide chains (A, B, and C), each encoded by a separate gene (C1QA; C1QB; C1QC). This complex is arranged in nine subunits (six disulfide-linked dimers of A and B, and three disulfide-linked homodimers of C). C1q has binding sites for antibodies (the heavy chain of IMMUNOGLOBULIN G or IMMUNOGLOBULIN M). The interaction of C1q and immunoglobulin activates the two proenzymes COMPLEMENT C1R and COMPLEMENT C1S, thus initiating the cascade of COMPLEMENT ACTIVATION via the CLASSICAL COMPLEMENT PATHWAY.
Molecules on the surface of some B-lymphocytes and macrophages, that recognize and combine with the C3b, C3d, C1q, and C4b components of complement.
Serine proteases that cleave COMPLEMENT C3 into COMPLEMENT C3A and COMPLEMENT C3B, or cleave COMPLEMENT C5 into COMPLEMENT C5A and COMPLEMENT C5B. These include the different forms of C3/C5 convertases in the classical and the alternative pathways of COMPLEMENT ACTIVATION. Both cleavages take place at the C-terminal of an ARGININE residue.
Complement activation initiated by the binding of COMPLEMENT C1 to ANTIGEN-ANTIBODY COMPLEXES at the COMPLEMENT C1Q subunit. This leads to the sequential activation of COMPLEMENT C1R and COMPLEMENT C1S subunits. Activated C1s cleaves COMPLEMENT C4 and COMPLEMENT C2 forming the membrane-bound classical C3 CONVERTASE (C4B2A) and the subsequent C5 CONVERTASE (C4B2A3B) leading to cleavage of COMPLEMENT C5 and the assembly of COMPLEMENT MEMBRANE ATTACK COMPLEX.
A 63-kDa serum glycoprotein encoded by gene C9. Monomeric C9 (mC9) binds the C5b-8 complex to form C5b-9 which catalyzes the polymerization of C9 forming C5b-p9 (MEMBRANE ATTACK COMPLEX) and transmembrane channels leading to lysis of the target cell. Patients with C9 deficiency suffer from recurrent bacterial infections.
Serum proteins that negatively regulate the cascade process of COMPLEMENT ACTIVATION. Uncontrolled complement activation and resulting cell lysis is potentially dangerous for the host. The complement system is tightly regulated by inactivators that accelerate the decay of intermediates and certain cell surface receptors.
A product of COMPLEMENT ACTIVATION cascade, regardless of the pathways, that forms transmembrane channels causing disruption of the target CELL MEMBRANE and cell lysis. It is formed by the sequential assembly of terminal complement components (COMPLEMENT C5B; COMPLEMENT C6; COMPLEMENT C7; COMPLEMENT C8; and COMPLEMENT C9) into the target membrane. The resultant C5b-8-poly-C9 is the "membrane attack complex" or MAC.
The smaller fragment generated from the cleavage of complement C3 by C3 CONVERTASE. C3a, a 77-amino acid peptide, is a mediator of local inflammatory process. It induces smooth MUSCLE CONTRACTION, and HISTAMINE RELEASE from MAST CELLS and LEUKOCYTES. C3a is considered an anaphylatoxin along with COMPLEMENT C4A; COMPLEMENT C5A; and COMPLEMENT C5A, DES-ARGININE.
The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.
Enzymes that activate one or more COMPLEMENT PROTEINS in the complement system leading to the formation of the COMPLEMENT MEMBRANE ATTACK COMPLEX, an important response in host defense. They are enzymes in the various COMPLEMENT ACTIVATION pathways.
A 53-kDa protein that is a positive regulator of the alternate pathway of complement activation (COMPLEMENT ACTIVATION PATHWAY, ALTERNATIVE). It stabilizes the ALTERNATIVE PATHWAY C3 CONVERTASE (C3bBb) and protects it from rapid inactivation, thus facilitating the cascade of COMPLEMENT ACTIVATION and the formation of MEMBRANE ATTACK COMPLEX. Individuals with mutation in the PFC gene exhibit properdin deficiency and have a high susceptibility to infections.
Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.
A 302-amino-acid fragment in the alpha chain (672-1663) of C3b. It is generated when C3b is inactivated (iC3b) and its alpha chain is cleaved by COMPLEMENT FACTOR I into C3c, and C3dg (955-1303) in the presence COMPLEMENT FACTOR H. Serum proteases further degrade C3dg into C3d (1002-1303) and C3g (955-1001).
Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.
Molecular sites on or in some B-lymphocytes and macrophages that recognize and combine with COMPLEMENT C3B. The primary structure of these receptors reveal that they contain transmembrane and cytoplasmic domains, with their extracellular portion composed entirely of thirty short consensus repeats each having 60 to 70 amino acids.
A screening assay for circulating COMPLEMENT PROTEINS. Diluted SERUM samples are added to antibody-coated ERYTHROCYTES and the percentage of cell lysis is measured. The values are expressed by the so called CH50, in HEMOLYTIC COMPLEMENT units per milliliter, which is the dilution of serum required to lyse 50 percent of the erythrocytes in the assay.
Compounds that negatively regulate the cascade process of COMPLEMENT ACTIVATION. Uncontrolled complement activation and resulting cell lysis is potentially dangerous for the host.
A syndrome that is associated with microvascular diseases of the KIDNEY, such as RENAL CORTICAL NECROSIS. It is characterized by hemolytic anemia (ANEMIA, HEMOLYTIC); THROMBOCYTOPENIA; and ACUTE RENAL FAILURE.
The first complement component to act in the activation of CLASSICAL COMPLEMENT PATHWAY. It is a calcium-dependent trimolecular complex made up of three subcomponents: COMPLEMENT C1Q; COMPLEMENT C1R; and COMPLEMENT C1S at 1:2:2 ratios. When the intact C1 binds to at least two antibodies (involving C1q), C1r and C1s are sequentially activated, leading to subsequent steps in the cascade of COMPLEMENT ACTIVATION.
The large fragment formed when COMPLEMENT C4 is cleaved by COMPLEMENT C1S. The membrane-bound C4b binds COMPLEMENT C2A, a SERINE PROTEASE, to form C4b2a (CLASSICAL PATHWAY C3 CONVERTASE) and subsequent C4b2a3b (CLASSICAL PATHWAY C5 CONVERTASE).
A transcriptional elongation factor complex that is comprised of a heterodimer of CYCLIN-DEPENDENT KINASE 9 and one of several CYCLINS including TYPE T CYCLINS and cyclin K. It functions by phosphorylating the carboxy-terminal domain of RNA POLYMERASE II.
A G-protein-coupled receptor that signals an increase in intracellular calcium in response to the potent ANAPHYLATOXIN peptide COMPLEMENT C5A.
A 105-kDa serum glycoprotein with significant homology to the other late complement components, C7-C9. It is a polypeptide chain cross-linked by 32 disulfide bonds. C6 is the next complement component to bind to the membrane-bound COMPLEMENT C5B in the assembly of MEMBRANE ATTACK COMPLEX. It is encoded by gene C6.
A 206-amino-acid fragment in the alpha chain (672-1663) of C3b. It is generated when C3b is inactivated (iC3b) and its alpha chain is cleaved by COMPLEMENT FACTOR I into C3c (749-954), and C3dg (955-1303) in the presence COMPLEMENT FACTOR H.
A 93-kDa serum glycoprotein encoded by C7 gene. It is a polypeptide chain with 28 disulfide bridges. In the formation of MEMBRANE ATTACK COMPLEX; C7 is the next component to bind the C5b-6 complex forming a trimolecular complex C5b-7 which is lipophilic, resembles an integral membrane protein, and serves as an anchor for the late complement components, C8 and C9.
Complement activation triggered by the interaction of microbial POLYSACCHARIDES with serum MANNOSE-BINDING LECTIN resulting in the activation of MANNOSE-BINDING PROTEIN-ASSOCIATED SERINE PROTEASES. As in the classical pathway, MASPs cleave COMPLEMENT C4 and COMPLEMENT C2 to form C3 CONVERTASE (C4B2A) and the subsequent C5 CONVERTASE (C4B2A3B) leading to cleavage of COMPLEMENT C5 and assembly of COMPLEMENT MEMBRANE ATTACK COMPLEX.
GPI-linked membrane proteins broadly distributed among hematopoietic and non-hematopoietic cells. CD55 prevents the assembly of C3 CONVERTASE or accelerates the disassembly of preformed convertase, thus blocking the formation of the membrane attack complex.
An endogenous 105-kDa plasma glycoprotein produced primarily by the LIVER and MONOCYTES. It inhibits a broad spectrum of proteases, including the COMPLEMENT C1R and the COMPLEMENT C1S proteases of the CLASSICAL COMPLEMENT PATHWAY, and the MANNOSE-BINDING PROTEIN-ASSOCIATED SERINE PROTEASES. C1-INH-deficient individuals suffer from HEREDITARY ANGIOEDEMA TYPES I AND II.
A 150-kDa serum glycoprotein composed of three subunits with each encoded by a different gene (C8A; C8B; and C8G). This heterotrimer contains a disulfide-linked C8alpha-C8gamma heterodimer and a noncovalently associated C8beta chain. C8 is the next component to bind the C5-7 complex forming C5b-8 that binds COMPLEMENT C9 and acts as a catalyst in the polymerization of C9.

Mutations of the type A domain of complement factor B that promote high-affinity C3b-binding. (1/379)

Factor B is a zymogen that carries the catalytic site of the complement alternative pathway convertases. During C3 convertase assembly, factor B associates with C3b and is cleaved at a single site by factor D. The Ba fragment is released, leaving the active complex, C3bBb. During the course of this process, the protease domain becomes activated. The type A domain of factor B, also part of Bb, is similar in structure to the type A domain of the complement receptor and integrin, CR3. Previously, mutations in the factor B type A domain were described that impair C3b-binding. This report describes "gain of function" mutations obtained by substituting factor B type A domain amino acids with homologous ones derived from the type A domain of CR3. Replacement of the betaA-alpha1 Mg2+ binding loop residue D254 with smaller amino acids, especially glycine, increased hemolytic activity and C3bBb stability. The removal of the oligosaccharide at position 260, near the Mg2+ binding cleft, when combined with the D254G substitution, resulted in increased affinity for C3b and iC3b, a C3b derivative. These findings offer strong evidence for the direct involvement of the type A domain in C3b binding, and are suggestive that steric effects of the D254 sidechain and the N260-linked oligosaccharide may contribute to the regulation of ligand binding.  (+info)

Complement activity in middle ear effusions. (2/379)

Evidence for complement utilization in middle ear fluids (MEF) from patients with otitis media with effusion was sought. It was found that cleavage products of C3, C4 and Factor B could be demonstrated immunochemically in MEF, and that native C3 was present in much lower concentrations than other proteins, relative to their serum concentrations. Haemolytic assays for C1-C5 showed that early complement components are inactivated in MEF. Potential mechanisms for complement utilization in MEF are discussed.  (+info)

Alterations in C3 activation and binding caused by phosphorylation by a casein kinase released from activated human platelets. (3/379)

A casein kinase released from activated human platelets phosphorylates a number of plasma proteins extracellularly, and that activation of platelets in systemic lupus erythematosus patients parallels an increase in the phosphate content of plasma proteins, including C3. The present study was undertaken to characterize this platelet protein kinase and to further elucidate the effect(s) on C3 function of phosphorylation by platelet casein kinase. The phosphate content of human plasma C3 was increased from 0.15 to 0.60 mol phosphate/mol of C3 after platelet activation in whole blood or platelet-rich plasma. The platelet casein kinase was distinct from other casein kinases in terms of its dependence on cations, inhibition by specific protein kinase inhibitors, and immunological reactivity. C3 that had been phosphorylated with platelet casein kinase was tested for its susceptibility to cleavage by trypsin or the classical and alternative pathway convertases and its binding to EAC and IgG. Phosphorylation did not affect the cleavage of C3 into C3a and C3b, but the binding of fragments from phosphorylated C3 to EAC14oxy2 cells and to IgG in purified systems and in serum was increased by 1.6-4.5 times over that of unphosphorylated C3. A covariation was seen between the enhanced binding of C3 fragments to IgG after phosphorylation and an increased ratio of glycerol/glycine binding, from 2.0 for unphosphorylated C3 to 4.9 for phosphorylated C3. The present study suggests that an overall effect of phosphorylation of C3 by platelet casein kinase is to enhance the opsonization of immune complexes.  (+info)

Pneumococcal surface protein A inhibits complement activation by Streptococcus pneumoniae. (4/379)

Pneumococcal surface protein A (PspA) is a surface-exposed protein virulence factor for Streptococcus pneumoniae. In this study, no significant depletion of serum complement was observed for the serum of mice infected with pneumococci that express PspA. In contrast, in mice infected with an isogenic strain of pneumococci lacking PspA, significant activation of serum complement was detected within 30 min after infection. Also, the PspA-deficient strain but not the PspA-expressing strain was cleared from the blood within 6 h. The contribution of PspA to pneumococcal virulence was further investigated by using mice deficient for C5, C3, or factor B. In mice deficient for C3 or factor B, PspA-negative pneumococci became fully virulent. In contrast, in C5-deficient mice as in wild-type mice, PspA-deficient pneumococci were avirulent. These in vivo data suggest that, in nonimmune mice infected with pneumococci, PspA interferes with complement-dependent host defense mechanisms mediated by factor B. Immunoblots of pneumococci opsonized in vitro suggested that more C3b was deposited on PspA-negative than on PspA-positive pneumococci. This was observed with and without anticapsular antibody. Furthermore, processing of the alpha chain of C3b was reduced in the presence of PspA. We propose that PspA exerts its virulence function by interfering with deposition of C3b onto pneumococci and/or by inhibiting formation of a fully functional alternative pathway C3 convertase. By blocking recruitment of the alternative pathway, PspA reduces the amount of C3b deposited onto pneumococci, thereby reducing the effectiveness of complement receptor-mediated pathways of clearance.  (+info)

Production and functional activity of a recombinant von Willebrand factor-A domain from human complement factor B. (5/379)

Factor B is a five-domain 90 kDa serine protease proenzyme which is part of the human serum complement system. It binds to other complement proteins C3b and properdin, and is activated by the protease factor D. The fourth domain of factor B is homologous to the type A domain of von Willebrand Factor (vWF-A). A full-length human factor B cDNA clone was used to amplify the region encoding the vWF-A domain (amino acids 229-444 of factor B). A fusion protein expression system was then used to generate it in high yield in Escherichia coli, where thrombin cleavage was used to separate the vWF-A domain from its fusion protein partner. A second vWF-A domain with improved stability and solubility was created using a Cys(267)-->Ser mutation and a four-residue C-terminal extension of the first vWF-A domain. The recombinant domains were investigated by analytical gel filtration, sucrose density centrifugation and analytical ultracentrifugation, in order to show that both domains were monomeric and possessed compact structures that were consistent with known vWF-A crystal structures. This expression system and its characterization permitted the first investigation of the function of the isolated vWF-A domain. It was able to inhibit substantially the binding of (125)I-labelled factor B to immobilized C3b. This demonstrated both the presence of a C3b binding site in this portion of factor B and a ligand-binding property of the vWF-A domain. The site at which factor D cleaves factor B is close to the N-terminus of both recombinant vWF-A domains. Factor D was shown to cleave the vWF-A domain in the presence or absence of C3b, whereas the cleavage of intact factor B under the same conditions occurs only in the presence of C3b.  (+info)

Sodium butyrate blocks interferon-gamma (IFN-gamma)-induced biosynthesis of MHC class III gene products (complement C4 and factor B) in human fetal intestinal epithelial cells. (6/379)

Human intestinal epithelial cells have been established as local sites for complement biosynthesis. In this study, we investigated the effects of IFN-gamma and sodium butyrate on biosynthesis of MHC class III gene products (complement C4 and factor B) in the human fetal intestinal epithelial cell line INT-407. IFN-gamma induced a dose- and time-dependent increase in C4 and factor B secretion. However, sodium butyrate dose-dependently inhibited IFN-gamma-induced C4 and factor B secretion. These effects were also observed at the mRNA level. Immunoblotting indicated that IFN-gamma induced a rapid activation of Stat1alpha, and fluorescence immunohistochemistry detected a translocation of Stat1alpha into the nucleus within 1 h. However, the translocation of Stat1alpha was not affected by the addition of sodium butyrate. Nuclear run-on assay indicated that IFN-gamma induced a weak increase in the transcription rate of factor B gene, and sodium butyrate did not affect this response. IFN-gamma and sodium butyrate induced a counter-regulatory effect on C4 and factor B secretion: IFN-gamma acted as a potent inducer, but sodium butyrate potently abrogated these responses. These are mainly regulated through the post-transcriptional mechanism.  (+info)

Counter-regulatory effect of sodium butyrate on tumour necrosis factor-alpha (TNF-alpha)-induced complement C3 and factor B biosynthesis in human intestinal epithelial cells. (7/379)

The various biological activities of butyrate have been well documented. In this study, we tested the effects of butyrate on TNF-alpha-induced complement C3 and factor B biosynthesis in human intestinal epithelial cells. The biosynthesis of C3, factor B and IL-8 was evaluated at the protein and mRNA levels. To evaluate transcriptional activation, the nuclear run-on assay was performed. The transcription factor-DNA binding activity was assessed by an electrophoretic gel mobility shift assay (EMSA). In the intestinal epithelial cell lines HT-29, T84 and Caco-2, sodium butyrate enhanced TNF-alpha-induced C3 secretion, but suppressed TNF-alpha-induced factor B and IL-8 secretion. Nuclear run-on assay revealed that transcriptional regulatory mechanisms are involved in the effects of sodium butyrate. The EMSAs indicated that sodium butyrate suppressed TNF-alpha-induced nuclear factor (NF)-kappaB- and activation protein (AP)-1-DNA binding activity, but enhanced TNF-alpha-induced activation of CCAAT/enhancer-binding protein (C/EBP)beta (NF-IL-6)-DNA binding activity. Sodium butyrate induced a counter-regulatory effect on TNF-alpha-induced C3 and factor B biosynthesis in human intestinal epithelial cells. Butyrate action has been discussed with its activity to induce histone hyperacetylation, but its counter-regulatory effect on complement biosynthesis may be closely associated with the modulation of transcription factor activation.  (+info)

Mutational analysis of the primary substrate specificity pocket of complement factor B. Asp(226) is a major structural determinant for p(1)-Arg binding. (8/379)

Factor B is a serine protease, which despite its trypsin-like specificity has Asn instead of the typical Asp at the bottom of the S(1) pocket (position 189, chymotrypsinogen numbering). Asp residues are present at positions 187 and 226 and either one could conceivably provide the negative charge for binding the P(1)-Arg of the substrate. Determination of the crystal structure of the factor B serine protease domain has revealed that the side chain of Asp(226) is within the S(1) pocket, whereas Asp(187) is located outside the pocket. To investigate the possible role of these atypical structural features in substrate binding and catalysis, we constructed a panel of mutants of these residues. Replacement of Asp(187) caused moderate (50-60%) decrease in hemolytic activity, compared with wild type factor B, whereas replacement of Asn(189) resulted in more profound reductions (71-95%). Substitutions at these two positions did not significantly affect assembly of the alternative pathway C3 convertase. In contrast, elimination of the negative charge from Asp(226) completely abrogated hemolytic activity and also affected formation of the C3 convertase. Kinetic analyses of the hydrolysis of a P(1)-Arg containing thioester by selected mutants confirmed that residue Asp(226) is a primary structural determinant for P(1)-Arg binding and catalysis.  (+info)

Complement Factor B is a protein that plays a crucial role in the complement system, which is a part of the immune system that helps to eliminate pathogens and damaged cells from the body. Specifically, Factor B is a component of the alternative pathway of the complement system, which provides a rapid and amplified response to microbial surfaces.

Factor B is cleaved by another protease called Factor D into two fragments, Ba and Bb. The formation of the C3 convertase (C3bBb) is essential for the activation of the alternative pathway. This complex can cleave and activate more C3 molecules, leading to a cascade of reactions that result in the formation of the membrane attack complex (MAC), which forms pores in the membranes of target cells, causing their lysis and elimination.

Deficiencies or mutations in Complement Factor B can lead to various complement-mediated diseases, such as atypical hemolytic uremic syndrome (aHUS) and age-related macular degeneration (AMD).

Complement C2 is a protein that plays a crucial role in the complement system, which is a part of the immune system that helps to eliminate pathogens and damaged cells from the body. Specifically, C2 is a component of the classical complement pathway, which is activated by the binding of antibodies to antigens on the surface of foreign particles or cells.

When the classical pathway is activated, C2 is cleaved into two fragments: C2a and C2b. C2a then binds to C4b to form the C3 convertase (C4b2a), which cleaves C3 into C3a and C3b. C3b can then go on to form the membrane attack complex, which creates a pore in the membrane of the target cell, leading to its lysis.

In summary, Complement C2 is a protein that helps to activate the complement system and destroy foreign particles or cells through the formation of the C3 convertase and the membrane attack complex.

Complement Factor H is a protein involved in the regulation of the complement system, which is a part of the immune system that helps to clear pathogens and damaged cells from the body. Specifically, Complement Factor H helps to regulate the activation and deactivation of the complement component C3b, preventing excessive or unwanted activation of the complement system and protecting host tissues from damage.

Complement Factor H is a crucial protein in maintaining the balance between the protective effects of the complement system and the potential for harm to the body's own cells and tissues. Deficiencies or mutations in Complement Factor H have been associated with several diseases, including age-related macular degeneration (AMD), atypical hemolytic uremic syndrome (aHUS), and C3 glomerulopathy.

Complement Factor D is a protein that plays a crucial role in the complement system, which is a part of the immune system that helps to clear pathogens and damaged cells from the body. Specifically, Factor D is a serine protease that is involved in the alternative pathway of the complement system.

In this pathway, Factor D helps to cleave another protein called Factor B, which then activates a complex called the C3 convertase. The C3 convertase cleaves complement component 3 (C3) into C3a and C3b, leading to the formation of the membrane attack complex (MAC), which creates a pore in the membrane of the target cell, causing its lysis and removal from the body.

Deficiencies or mutations in Complement Factor D can lead to an impaired alternative pathway and increased susceptibility to certain infections, particularly those caused by Neisseria bacteria. Additionally, abnormal regulation of the complement system has been implicated in a variety of diseases, including autoimmune disorders, inflammatory conditions, and neurodegenerative diseases.

Complement C3b is a protein fragment that plays a crucial role in the complement system, which is a part of the immune system that helps to clear pathogens and damaged cells from the body. C3b is generated during the activation of the complement system, particularly via the classical, lectin, and alternative pathways.

Once formed, C3b can bind covalently to the surface of microbes or other target particles, marking them for destruction by other components of the immune system. Additionally, C3b can interact with other proteins in the complement system to generate the membrane attack complex (MAC), which forms pores in the membranes of targeted cells, leading to their lysis and removal.

In summary, Complement C3b is a vital protein fragment involved in the recognition, tagging, and elimination of pathogens and damaged cells during the immune response.

Complement C3 Convertase, Alternative Pathway is a complex enzyme composed of the proteins C3b and Bb. It plays a crucial role in the alternative pathway of the complement system, which is a part of the innate immune system that helps to defend the body against invading pathogens.

The alternative pathway is continuously activated at a low level, and C3 Convertase is responsible for amplifying this activation. It does so by cleaving the complement component C3 into C3a and C3b. The C3b then binds to the surface of the pathogen and can form additional C3 Convertases, leading to a positive feedback loop that results in the rapid accumulation of complement components on the surface of the pathogen.

This accumulation of complement components helps to mark the pathogen for destruction by other immune cells, such as neutrophils and macrophages. Additionally, the cleavage products C3a and C5a generated during this process can act as anaphylatoxins, inducing inflammation and attracting more immune cells to the site of infection.

Regulation of Complement C3 Convertase is critical to prevent damage to host tissues. Several regulatory proteins, such as factor H and decay-accelerating factor (DAF), help to limit the formation and activity of C3 Convertase on host cells and tissues. Dysregulation of the complement system, including the alternative pathway and Complement C3 Convertase, has been implicated in a variety of diseases, including autoimmune disorders, inflammatory diseases, and infectious diseases.

Complement C3 is a protein that plays a central role in the complement system, which is a part of the immune system that helps to clear pathogens and damaged cells from the body. Complement C3 can be activated through three different pathways: the classical pathway, the lectin pathway, and the alternative pathway. Once activated, it breaks down into two fragments, C3a and C3b.

C3a is an anaphylatoxin that helps to recruit immune cells to the site of infection or injury, while C3b plays a role in opsonization, which is the process of coating pathogens or damaged cells with proteins to make them more recognizable to the immune system. Additionally, C3b can also activate the membrane attack complex (MAC), which forms a pore in the membrane of target cells leading to their lysis or destruction.

In summary, Complement C3 is an important protein in the complement system that helps to identify and eliminate pathogens and damaged cells from the body through various mechanisms.

The alternative complement pathway is one of the three initiating pathways of the complement system, which is a part of the innate immune system that helps to clear pathogens and damaged cells from the body. The other two pathways are the classical and lectin pathways.

The alternative pathway is continuously activated at a low level, even in the absence of infection or injury, through the spontaneous cleavage of complement component C3 into C3a and C3b by the protease factor D in the presence of magnesium ions. The generated C3b can then bind covalently to nearby surfaces, including pathogens and host cells.

On self-surfaces, regulatory proteins like decay-accelerating factor (DAF) or complement receptor 1 (CR1) help to prevent the formation of the alternative pathway convertase and thus further activation of the complement system. However, on foreign surfaces, the C3b can recruit more complement components, forming a complex called the alternative pathway convertase (C3bBb), which cleaves additional C3 molecules into C3a and C3b.

The generated C3b can then bind to the surface and participate in the formation of the membrane attack complex (MAC), leading to the lysis of the target cell. The alternative pathway plays a crucial role in the defense against gram-negative bacteria, fungi, and parasites, as well as in the clearance of immune complexes and apoptotic cells. Dysregulation of the alternative complement pathway has been implicated in several diseases, including autoimmune disorders and atypical hemolytic uremic syndrome (aHUS).

Complement activation is the process by which the complement system, a part of the immune system, is activated to help eliminate pathogens and damaged cells from the body. The complement system consists of a group of proteins that work together to recognize and destroy foreign substances.

Activation of the complement system can occur through three different pathways: the classical pathway, the lectin pathway, and the alternative pathway. Each pathway involves a series of proteolytic reactions that ultimately result in the formation of the membrane attack complex (MAC), which creates a pore in the membrane of the target cell, leading to its lysis and removal.

The classical pathway is typically activated by the binding of antibodies to antigens on the surface of a pathogen or damaged cell. The lectin pathway is activated by the recognition of specific carbohydrate structures on the surface of microorganisms. The alternative pathway can be spontaneously activated and serves as an amplification loop for both the classical and lectin pathways.

Complement activation plays a crucial role in the immune response, but uncontrolled or excessive activation can also lead to tissue damage and inflammation. Dysregulation of complement activation has been implicated in various diseases, including autoimmune disorders, inflammatory conditions, and neurodegenerative diseases.

Complement Factor I is a protein involved in the regulation of the complement system, which is a part of the immune system that helps to clear pathogens and damaged cells from the body. Specifically, Complement Factor I is a serine protease that regulates the complement component C3b by cleaving it into inactive fragments, thereby preventing the excessive activation of the complement system and protecting host tissues from damage.

Complement Factor I functions in conjunction with other regulatory proteins, such as complement receptor 1 (CR1) and membrane cofactor protein (MCP), to control the activity of the complement system at various stages. Deficiencies or mutations in Complement Factor I have been associated with several diseases, including atypical hemolytic uremic syndrome (aHUS), age-related macular degeneration (AMD), and systemic lupus erythematosus (SLE).

Macular degeneration, also known as age-related macular degeneration (AMD), is a medical condition that affects the central part of the retina, called the macula. The macula is responsible for sharp, detailed vision, which is necessary for activities such as reading, driving, and recognizing faces.

In AMD, there is a breakdown or deterioration of the macula, leading to gradual loss of central vision. There are two main types of AMD: dry (atrophic) and wet (exudative). Dry AMD is more common and progresses more slowly, while wet AMD is less common but can cause rapid and severe vision loss if left untreated.

The exact causes of AMD are not fully understood, but risk factors include age, smoking, family history, high blood pressure, obesity, and exposure to sunlight. While there is no cure for AMD, treatments such as vitamin supplements, laser therapy, and medication injections can help slow its progression and reduce the risk of vision loss.

Cobra venoms are a type of snake venom that is produced by cobras, which are members of the genus Naja in the family Elapidae. These venoms are complex mixtures of proteins and other molecules that have evolved to help the snake immobilize and digest its prey.

Cobra venoms typically contain a variety of toxic components, including neurotoxins, hemotoxins, and cytotoxins. Neurotoxins target the nervous system and can cause paralysis and respiratory failure. Hemotoxins damage blood vessels and tissues, leading to internal bleeding and organ damage. Cytotoxins destroy cells and can cause tissue necrosis.

The specific composition of cobra venoms can vary widely between different species of cobras, as well as between individual snakes of the same species. Some cobras have venoms that are primarily neurotoxic, while others have venoms that are more hemotoxic or cytotoxic. The potency and effects of cobra venoms can also be influenced by factors such as the age and size of the snake, as well as the temperature and pH of the environment.

Cobra bites can be extremely dangerous and even fatal to humans, depending on the species of cobra, the amount of venom injected, and the location of the bite. Immediate medical attention is required in the event of a cobra bite, including the administration of antivenom therapy to neutralize the effects of the venom.

The complement system is a group of proteins found in the blood and on the surface of cells that when activated, work together to help eliminate pathogens such as bacteria, viruses, and fungi from the body. The proteins are normally inactive in the bloodstream. When they encounter an invading microorganism or foreign substance, a series of reactions take place leading to the activation of the complement system. Activation results in the production of effector molecules that can punch holes in the cell membranes of pathogens, recruit and activate immune cells, and help remove debris and dead cells from the body.

There are three main pathways that can lead to complement activation: the classical pathway, the lectin pathway, and the alternative pathway. Each pathway involves a series of proteins that work together in a cascade-like manner to amplify the response and generate effector molecules. The three main effector molecules produced by the complement system are C3b, C4b, and C5b. These molecules can bind to the surface of pathogens, marking them for destruction by other immune cells.

Complement proteins also play a role in the regulation of the immune response. They help to prevent excessive activation of the complement system, which could damage host tissues. Dysregulation of the complement system has been implicated in a number of diseases, including autoimmune disorders and inflammatory conditions.

In summary, Complement System Proteins are a group of proteins that play a crucial role in the immune response by helping to eliminate pathogens and regulate the immune response. They can be activated through three different pathways, leading to the production of effector molecules that mark pathogens for destruction. Dysregulation of the complement system has been linked to various diseases.

Complement C4 is a protein that plays a crucial role in the complement system, which is a part of the immune system that helps to clear pathogens and damaged cells from the body. Complement C4 is involved in the early stages of the complement activation cascade, where it helps to identify and tag foreign or abnormal cells for destruction by other components of the immune system.

Specifically, Complement C4 can be cleaved into two smaller proteins, C4a and C4b, during the complement activation process. C4b then binds to the surface of the target cell and helps to initiate the formation of the membrane attack complex (MAC), which creates a pore in the cell membrane and leads to lysis or destruction of the target cell.

Deficiencies or mutations in the Complement C4 gene can lead to various immune disorders, including certain forms of autoimmune diseases and susceptibility to certain infections.

Complement C3b inactivator proteins, also known as complement regulators or decay-accelerating factor (DAF), are a group of proteins that play a crucial role in regulating the complement system. The complement system is a part of the immune system that helps to eliminate pathogens and damaged cells from the body.

The complement C3b inactivator proteins include two main types: complement receptor 1 (CR1) and decay-accelerating factor (DAF). These proteins work by regulating the formation of the membrane attack complex (MAC), a protein structure that forms pores in the cell membrane, leading to cell lysis.

Complement C3b inactivator proteins bind to C3b and C4b components of the complement system, preventing them from forming the MAC. By doing so, they help to prevent excessive activation of the complement system, which can damage healthy cells and tissues.

Deficiencies or dysfunction of complement C3b inactivator proteins have been associated with several diseases, including autoimmune disorders, inflammatory diseases, and infectious diseases. Therefore, understanding the role of these proteins in regulating the complement system is essential for developing new therapies to treat these conditions.

Complement C5 is a protein that plays a crucial role in the complement system, which is a part of the immune system that helps to eliminate pathogens and damaged cells from the body. The complement system is a complex series of biochemical reactions that help to identify and destroy foreign substances, such as bacteria and viruses.

Complement C5 is one of several proteins in the complement system that are activated in a cascading manner in response to an activating event, such as the binding of an antibody to a pathogen. Once activated, Complement C5 can be cleaved into two smaller proteins, C5a and C5b.

C5a is a powerful anaphylatoxin, which means it can cause the release of histamine from mast cells and basophils, leading to inflammation and increased vascular permeability. It also acts as a chemoattractant, drawing immune cells to the site of infection or injury.

C5b, on the other hand, plays a role in the formation of the membrane attack complex (MAC), which is a protein structure that can punch holes in the membranes of pathogens, leading to their lysis and destruction.

Overall, Complement C5 is an important component of the immune system's response to infection and injury, helping to eliminate pathogens and damaged cells from the body.

Enzyme precursors are typically referred to as zymogens or proenzymes. These are inactive forms of enzymes that can be activated under specific conditions. When the need for the enzyme's function arises, the proenzyme is converted into its active form through a process called proteolysis, where it is cleaved by another enzyme. This mechanism helps control and regulate the activation of certain enzymes in the body, preventing unwanted or premature reactions. A well-known example of an enzyme precursor is trypsinogen, which is converted into its active form, trypsin, in the digestive system.

Complement C5a is a protein fragment that is generated during the activation of the complement system, which is a part of the immune system. The complement system helps to eliminate pathogens and damaged cells from the body by tagging them for destruction and attracting immune cells to the site of infection or injury.

C5a is formed when the fifth component of the complement system (C5) is cleaved into two smaller fragments, C5a and C5b, during the complement activation cascade. C5a is a potent pro-inflammatory mediator that can attract and activate various immune cells, such as neutrophils, monocytes, and eosinophils, to the site of infection or injury. It can also increase vascular permeability, promote the release of histamine, and induce the production of reactive oxygen species, all of which contribute to the inflammatory response.

However, excessive or uncontrolled activation of the complement system and generation of C5a can lead to tissue damage and inflammation, contributing to the pathogenesis of various diseases, such as sepsis, acute respiratory distress syndrome (ARDS), and autoimmune disorders. Therefore, targeting C5a or its receptors has been explored as a potential therapeutic strategy for these conditions.

Complement C1q is a protein that is part of the complement system, which is a group of proteins in the blood that help to eliminate pathogens and damaged cells from the body. C1q is the first component of the classical complement pathway, which is activated by the binding of C1q to antibodies that are attached to the surface of a pathogen or damaged cell.

C1q is composed of six identical polypeptide chains, each containing a collagen-like region and a globular head region. The globular heads can bind to various structures, including the Fc regions of certain antibodies, immune complexes, and some types of cells. When C1q binds to an activating surface, it triggers a series of proteolytic reactions that lead to the activation of other complement components and the formation of the membrane attack complex (MAC), which can punch holes in the membranes of pathogens or damaged cells, leading to their destruction.

In addition to its role in the immune system, C1q has also been found to have roles in various physiological processes, including tissue remodeling, angiogenesis, and the clearance of apoptotic cells. Dysregulation of the complement system, including abnormalities in C1q function, has been implicated in a variety of diseases, including autoimmune disorders, inflammatory diseases, and neurodegenerative conditions.

Complement receptors are proteins found on the surface of various cells in the human body, including immune cells and some non-immune cells. They play a crucial role in the complement system, which is a part of the innate immune response that helps to eliminate pathogens and damaged cells from the body. Complement receptors bind to complement proteins or fragments that are generated during the activation of the complement system. This binding triggers various intracellular signaling events that can lead to diverse cellular responses, such as phagocytosis, inflammation, and immune regulation.

There are several types of complement receptors, including:

1. CR1 (CD35): A receptor found on erythrocytes, B cells, neutrophils, monocytes, macrophages, and glomerular podocytes. It functions in the clearance of immune complexes and regulates complement activation.
2. CR2 (CD21): Expressed mainly on B cells and follicular dendritic cells. It facilitates antigen presentation, B-cell activation, and immune regulation.
3. CR3 (CD11b/CD18, Mac-1): Present on neutrophils, monocytes, macrophages, and some T cells. It mediates cell adhesion, phagocytosis, and intracellular signaling.
4. CR4 (CD11c/CD18, p150,95): Expressed on neutrophils, monocytes, macrophages, and dendritic cells. It is involved in cell adhesion, phagocytosis, and intracellular signaling.
5. C5aR (CD88): Found on various immune cells, including neutrophils, monocytes, macrophages, mast cells, eosinophils, and dendritic cells. It binds to the complement protein C5a and mediates chemotaxis, degranulation, and inflammation.
6. C5L2 (GPR77): Present on various cell types, including immune cells. Its function is not well understood but may involve regulating C5a-mediated responses or acting as a receptor for other ligands.

These receptors play crucial roles in the immune response and inflammation by mediating various functions such as chemotaxis, phagocytosis, cell adhesion, and intracellular signaling. Dysregulation of these receptors has been implicated in several diseases, including autoimmune disorders, infections, and cancer.

Complement C3-C5 convertases are proteins that play a crucial role in the activation of the complement system, which is a part of the immune system. The complement system helps to eliminate pathogens and damaged cells from the body by marking them for destruction and attracting immune cells to the site of infection or injury.

The C3-C5 convertases are formed during the activation of the complement component 3 (C3) protein, which is a central player in the complement system. The formation of the C3-C5 convertase involves two main steps:

1. C3 convertase formation: In this step, a complex of proteins called the C3 convertase is formed by the cleavage of C3 into C3a and C3b fragments. This complex can then cleave additional C3 molecules into C3a and C3b fragments, amplifying the complement response.
2. C5 convertase formation: In this step, the C3b fragment from the C3 convertase binds to another protein called C4b2a, forming a new complex called the C5 convertase. The C5 convertase can then cleave the C5 protein into C5a and C5b fragments.

The C5b fragment goes on to form the membrane attack complex (MAC), which creates a pore in the membrane of the target cell, leading to its lysis or destruction. The C3a and C5a fragments are small proteins called anaphylatoxins that can cause inflammation and attract immune cells to the site of infection or injury.

Overall, the formation of Complement C3-C5 convertases is a critical step in the activation of the complement system and plays a key role in the body's defense against pathogens and damaged cells.

The "Classical Complement Pathway" is one of the three pathways that make up the complement system, which is a part of the immune system in humans and other animals. The complement system helps to enhance the ability of antibodies and phagocytic cells to clear pathogens from the body.

The Classical Complement Pathway is initiated by the binding of the first component of the complement system, C1, to an activator surface, such as an antigen-antibody complex. Activation of C1 results in the sequential activation of other components of the complement system, including C4 and C2, which form the C3 convertase (C4b2a). The C3 convertase cleaves the third component of the complement system, C3, into C3a and C3b. C3b then binds to the activator surface and forms a complex with other components of the complement system, leading to the formation of the membrane attack complex (MAC), which creates a pore in the membrane of the target cell, causing its lysis.

The Classical Complement Pathway plays an important role in the immune response to pathogens and can also contribute to inflammation and tissue damage in certain diseases, such as autoimmune disorders and allergies.

Complement C9 is a protein that plays a crucial role in the complement system, which is a part of the immune system that helps to eliminate pathogens and damaged cells from the body. Specifically, C9 is one of the components of the membrane attack complex (MAC), which is a protein structure that forms pores in the membranes of target cells, leading to their lysis or destruction.

When activated, C9 polymerizes and inserts itself into the cell membrane, forming a transmembrane pore that disrupts the membrane's integrity and causes the cell to lyse. This process is an essential part of the complement system's ability to destroy pathogens and clear damaged cells from the body.

Defects in the C9 gene can lead to a rare genetic disorder called complement component 9 deficiency, which is characterized by recurrent bacterial infections and immune complex-mediated diseases. Additionally, mutations in the C9 gene have been associated with an increased risk of age-related macular degeneration (AMD), a leading cause of blindness in older adults.

Complement inactivator proteins are a group of regulatory proteins that help to control and limit the activation of the complement system, which is a part of the immune system. The complement system is a complex series of biochemical reactions that help to eliminate pathogens and damaged cells from the body. However, if not properly regulated, the complement system can also cause damage to healthy tissues and contribute to the development of various diseases.

Complement inactivator proteins work by inhibiting specific components of the complement system, preventing them from activating and causing an immune response. Some examples of complement inactivator proteins include:

1. C1 inhibitor (C1INH): This protein regulates the activation of the classical pathway of the complement system by inhibiting the C1 complex, which is a group of proteins that initiate this pathway.
2. Decay-accelerating factor (DAF or CD55): This protein regulates the activation of both the classical and alternative pathways of the complement system by accelerating the decay of the C3/C5 convertases, which are enzymes that activate the complement components C3 and C5.
3. Membrane cofactor protein (MCP or CD46): This protein regulates the activation of the alternative pathway of the complement system by serving as a cofactor for the cleavage and inactivation of C3b, a component of the C3 convertase.
4. Factor H: This protein also regulates the activation of the alternative pathway of the complement system by acting as a cofactor for the cleavage and inactivation of C3b, and by preventing the formation of the C3 convertase.

Deficiencies or dysfunction of complement inactivator proteins can lead to various diseases, including hereditary angioedema (C1INH deficiency), atypical hemolytic uremic syndrome (factor H deficiency or dysfunction), and age-related macular degeneration (complement component overactivation).

The Complement Membrane Attack Complex (MAC), also known as the Terminal Complement Complex (TCC), is a protein structure that forms in the final stages of the complement system's immune response. The complement system is a part of the innate immune system that helps to eliminate pathogens and damaged cells from the body.

The MAC is composed of several proteins, including C5b, C6, C7, C8, and multiple subunits of C9, which assemble on the surface of target cells. The formation of the MAC creates a pore-like structure in the cell membrane, leading to disruption of the membrane's integrity and ultimately causing cell lysis or damage.

The MAC plays an important role in the immune response by helping to eliminate pathogens that have evaded other immune defenses. However, uncontrolled activation of the complement system and formation of the MAC can also contribute to tissue damage and inflammation in various diseases, such as autoimmune disorders, age-related macular degeneration, and ischemia-reperfusion injury.

Complement C3a is a protein fragment that is generated during the activation of the complement system, which is a part of the immune system. The complement system helps to eliminate pathogens and damaged cells from the body by marking them for destruction and attracting immune cells to the site of infection or injury.

C3a is produced when the third component of the complement system (C3) is cleaved into two smaller fragments, C3a and C3b, during the complement activation cascade. C3a is a potent anaphylatoxin, which means it can cause the release of histamine and other mediators from mast cells and basophils, leading to inflammation, increased vascular permeability, and smooth muscle contraction.

C3a also has chemotactic properties, meaning it can attract immune cells such as neutrophils and monocytes to the site of complement activation. Additionally, C3a can modulate the activity of various immune cells, including dendritic cells, T cells, and B cells, and play a role in the regulation of the adaptive immune response.

It's important to note that while C3a has important functions in the immune response, uncontrolled or excessive activation of the complement system can lead to tissue damage and inflammation, contributing to the pathogenesis of various diseases such as autoimmune disorders, inflammatory diseases, and allergies.

An amino acid sequence is the specific order of amino acids in a protein or peptide molecule, formed by the linking of the amino group (-NH2) of one amino acid to the carboxyl group (-COOH) of another amino acid through a peptide bond. The sequence is determined by the genetic code and is unique to each type of protein or peptide. It plays a crucial role in determining the three-dimensional structure and function of proteins.

Complement activating enzymes are proteins that play a crucial role in the activation of the complement system, which is a part of the immune system. The complement system is a complex series of biochemical reactions that help to eliminate pathogens and damaged cells from the body.

There are several types of complement activating enzymes, including:

1. Classical pathway activators: These include the C1, C4, and C2 components of the complement system. When activated, they trigger a series of reactions that lead to the formation of the membrane attack complex (MAC), which creates a pore in the membrane of the target cell, leading to its lysis.
2. Alternative pathway activators: These include factors B, D, and P. They are constantly active at low levels and can be activated by surfaces that are not normally found in the body, such as bacterial cell walls. Once activated, they also trigger the formation of the MAC.
3. Lectin pathway activators: These include mannose-binding lectin (MBL) and ficolins. They bind to carbohydrates on the surface of microbes and activate the complement system through the MBL-associated serine proteases (MASPs).

Overall, complement activating enzymes play a critical role in the immune response by helping to identify and eliminate pathogens and damaged cells from the body.

Properdin is defined as a positive regulatory protein in the complement system, which is a part of the immune system. It plays a crucial role in the alternative pathway of complement activation. Properdin stabilizes the C3 convertase (C3bBb), preventing its decay and increasing the efficiency of the alternative pathway. This results in the production of the membrane attack complex, which leads to the lysis of foreign cells or pathogens. Deficiencies in properdin can lead to an increased susceptibility to bacterial infections.

A peptide fragment is a short chain of amino acids that is derived from a larger peptide or protein through various biological or chemical processes. These fragments can result from the natural breakdown of proteins in the body during regular physiological processes, such as digestion, or they can be produced experimentally in a laboratory setting for research or therapeutic purposes.

Peptide fragments are often used in research to map the structure and function of larger peptides and proteins, as well as to study their interactions with other molecules. In some cases, peptide fragments may also have biological activity of their own and can be developed into drugs or diagnostic tools. For example, certain peptide fragments derived from hormones or neurotransmitters may bind to receptors in the body and mimic or block the effects of the full-length molecule.

Complement C3d is a protein fragment that is formed during the activation of the complement system, which is a part of the immune system. The complement system helps to eliminate pathogens such as bacteria and viruses from the body by tagging them for destruction and attracting immune cells to the site of infection.

C3d is a cleavage product of complement component C3, which is one of the central proteins in the complement system. When C3 is activated, it is cleaved into two fragments: C3a and C3b. C3b can then be further cleaved into C3d and C3c.

C3d plays a role in the activation of the immune system by helping to link the complement system with the adaptive immune response. It does this by binding to receptors on B cells, which are a type of white blood cell that produces antibodies. This interaction can help to stimulate the production of antibodies and enhance the immune response to pathogens.

C3d has also been implicated in the development of certain autoimmune diseases, as it can contribute to the formation of immune complexes that can cause tissue damage.

Molecular sequence data refers to the specific arrangement of molecules, most commonly nucleotides in DNA or RNA, or amino acids in proteins, that make up a biological macromolecule. This data is generated through laboratory techniques such as sequencing, and provides information about the exact order of the constituent molecules. This data is crucial in various fields of biology, including genetics, evolution, and molecular biology, allowing for comparisons between different organisms, identification of genetic variations, and studies of gene function and regulation.

Complement receptor 3b (CR3b or CD11b/CD18) is not a medical definition itself, but I can provide you with the relevant information regarding this term.

Complement receptor 3 (CR3) is a heterodimeric receptor consisting of two subunits, CD11b (also known as Mac-1 or CR3 alpha) and CD18 (also known as beta2 integrin). There are two forms of the CD11b/CD18 heterodimer: CR3a (CD11b/CD18) and CR3b (CD11b/CD18'). The difference between these two forms lies in the conformation of the CD11b subunit.

Complement receptor 3b (CR3b or CD11b/CD18') is a less common form of the CR3 receptor, which is primarily expressed on myeloid cells such as monocytes, macrophages, and neutrophils. CR3b has a higher affinity for complement component C3b and its fragments iC3b and C3dg compared to CR3a.

CR3b plays a role in various immune functions, including:

1. Phagocytosis: Binding of C3b or its fragments to CR3b facilitates the recognition and uptake of opsonized pathogens by phagocytes.
2. Adhesion: The integrin component of CR3b mediates cell-cell and cell-matrix interactions, contributing to leukocyte migration and recruitment to sites of inflammation or infection.
3. Intracellular signaling: Activation of CR3b can lead to intracellular signaling events that modulate immune responses, such as the release of pro-inflammatory cytokines and reactive oxygen species.

In summary, Complement receptor 3b (CR3b or CD11b/CD18') is a less common form of CR3 primarily expressed on myeloid cells that binds complement component C3b and its fragments with high affinity, mediating phagocytosis, adhesion, and intracellular signaling.

A Complement Hemolytic Activity Assay is a laboratory test used to measure the functionality and activity level of the complement system, which is a part of the immune system. The complement system is a group of proteins that work together to help eliminate pathogens from the body.

The assay measures the ability of the complement system to lyse (break open) red blood cells. This is done by mixing the patient's serum (the liquid portion of the blood) with antibody-coated red blood cells and incubating them together. The complement proteins in the serum will then bind to the antibodies on the red blood cells and cause them to lyse.

The degree of hemolysis (red blood cell lysis) is directly proportional to the activity level of the complement system. By measuring the amount of hemolysis, the assay can determine whether the complement system is functioning properly and at what level of activity.

This test is often used to diagnose or monitor complement-mediated diseases such as autoimmune disorders, infections, and some types of cancer. It may also be used to evaluate the effectiveness of treatments that target the complement system.

Complement inactivating agents are substances or drugs that inhibit the complement system, which is a part of the immune system responsible for the recognition and elimination of foreign substances and microorganisms. The complement system consists of a group of proteins that work together to help eliminate pathogens from the body.

Complement inactivating agents are used in medical settings to prevent or treat various conditions associated with excessive or unwanted activation of the complement system, such as inflammation, autoimmune diseases, and transplant rejection. These agents can inhibit different components of the complement pathway, including C1 esterase inhibitors, C3 convertase inhibitors, and C5a receptor antagonists.

Examples of complement inactivating agents include eculizumab, ravulizumab, and Alexion's Ultomiris, which are monoclonal antibodies that target C5, a protein involved in the final steps of the complement pathway. These drugs have been approved for the treatment of paroxysmal nocturnal hemoglobinuria (PNH), atypical hemolytic uremic syndrome (aHUS), and other complement-mediated diseases.

Other complement inactivating agents include C1 esterase inhibitors, such as Berinert and Ruconest, which are used to treat hereditary angioedema (HAE). These drugs work by inhibiting the activation of the classical pathway of the complement system, thereby preventing the release of inflammatory mediators that can cause swelling and pain.

Overall, complement inactivating agents play an important role in the treatment of various complement-mediated diseases, helping to reduce inflammation, prevent tissue damage, and improve patient outcomes.

Hemolytic-Uremic Syndrome (HUS) is a serious condition that affects the blood and kidneys. It is characterized by three major features: the breakdown of red blood cells (hemolysis), the abnormal clotting of small blood vessels (microthrombosis), and acute kidney failure.

The breakdown of red blood cells leads to the release of hemoglobin into the bloodstream, which can cause anemia. The microthrombi can obstruct the flow of blood in the kidneys' filtering system (glomeruli), leading to damaged kidney function and potentially acute kidney failure.

HUS is often caused by a bacterial infection, most commonly Escherichia coli (E. coli) that produces Shiga toxins. This form of HUS is known as STEC-HUS or Stx-HUS. Other causes include infections with other bacteria, viruses, medications, pregnancy complications, and certain medical conditions such as autoimmune diseases.

Symptoms of HUS may include fever, fatigue, decreased urine output, blood in the stool, swelling in the face, hands, or feet, and irritability or confusion. Treatment typically involves supportive care, including dialysis for kidney failure, transfusions to replace lost red blood cells, and managing high blood pressure. In severe cases, a kidney transplant may be necessary.

Complement C1 is a protein complex that plays a crucial role in the complement system, which is a part of the immune system that helps to eliminate pathogens and damaged cells from the body. The complement system consists of a group of proteins that work together to destroy microbes and remove debris.

Complement C1 is composed of three subunits: C1q, C1r, and C1s. When activated, C1q binds to the surface of a pathogen or damaged cell, leading to the activation of C1r and C1s. Activated C1r then cleaves and activates C1s, which in turn cleaves and activates other complement components, ultimately resulting in the formation of the membrane attack complex (MAC), a protein structure that forms a pore in the membrane of the target cell, leading to its lysis and destruction.

Defects in the complement component C1 can lead to immune disorders, such as hereditary angioedema, which is characterized by recurrent episodes of swelling in various parts of the body.

Complement C4b is a protein fragment that is formed during the activation of the complement system, which is a part of the immune system. The complement system helps to eliminate pathogens and damaged cells from the body by tagging them for destruction and attracting immune cells to the site of infection or injury.

C4b is generated when the C4 protein is cleaved into two smaller fragments, C4a and C4b, during the activation of the classical or lectin pathways of the complement system. C4b then binds covalently to the surface of the target cell or pathogen, forming a complex with other complement proteins that can create a membrane attack complex (MAC) and cause cell lysis.

C4b can also act as an opsonin, coating the surface of the target cell or pathogen and making it easier for immune cells to recognize and phagocytose them. Additionally, C4b can activate the alternative pathway of the complement system, leading to further amplification of the complement response.

Positive Transcriptional Elongation Factor B (P-TEFb) is a crucial protein complex in the process of transcription, which is the first step in gene expression. The main function of P-TEFb is to help RNA polymerase II, the enzyme responsible for transcribing DNA into RNA, to continue and complete the transcription of genes.

P-TEFb is composed of two subunits: cyclin T (CYCT) and CDK9 (cyclin-dependent kinase 9). The complex acts by phosphorylating several proteins that associate with RNA polymerase II, including the negative elongation factors NELF and DSIF. This phosphorylation converts NELF from a repressor to an activator of transcription elongation and relieves DSIF-mediated pausing of RNA polymerase II, allowing it to transcribe genes efficiently.

P-TEFb plays a significant role in regulating the expression of numerous genes, including those involved in cell growth, differentiation, and survival. Its dysregulation has been implicated in several diseases, such as cancer and HIV infection. In cancer, P-TEFb can contribute to oncogene activation and tumor progression, while in HIV, it is required for the transcription of viral genes during the early and late stages of infection.

The term "Receptor, Anaphylatoxin C5a" refers to a specific type of receptor found on the surface of various cells in the human body, including immune cells and endothelial cells. This receptor binds to a molecule called C5a, which is a cleavage product of the complement component C5 and is one of the most potent anaphylatoxins.

Anaphylatoxins are inflammatory mediators that play a crucial role in the immune response, particularly in the activation of the complement system and the recruitment of immune cells to sites of infection or injury. C5a is generated during the activation of the complement system and has a wide range of biological activities, including chemotaxis (attracting immune cells to the site of inflammation), increased vascular permeability, and the activation of immune cells such as neutrophils, monocytes, and mast cells.

The C5a receptor, also known as CD88, is a G protein-coupled receptor that belongs to the superfamily of seven transmembrane domain receptors. When C5a binds to the receptor, it triggers a series of intracellular signaling events that lead to the activation of various cellular responses, such as the release of inflammatory mediators and the recruitment of immune cells to the site of inflammation.

Abnormal activation of the C5a/C5a receptor pathway has been implicated in a variety of inflammatory diseases, including sepsis, acute respiratory distress syndrome (ARDS), and autoimmune disorders. Therefore, targeting this pathway with therapeutic agents has emerged as a promising strategy for the treatment of these conditions.

Complement C6 is a protein that plays a crucial role in the complement system, which is a part of the immune system that helps to eliminate pathogens and damaged cells from the body. Specifically, C6 is a component of the membrane attack complex (MAC), which is a group of proteins that work together to form a pore in the membrane of target cells, leading to their lysis or destruction.

The complement system is activated through several different pathways, including the classical pathway, the lectin pathway, and the alternative pathway. Once activated, these pathways converge at the level of C3, which is cleaved into C3a and C3b fragments. C3b can then bind to the surface of target cells and initiate the formation of the MAC.

C6 is one of several proteins that are required for the formation of the MAC. When C6 binds to C7, it undergoes a conformational change that allows it to interact with C8 and form a stable complex. This complex then recruits additional C9 molecules, which polymerize to form the pore in the target cell membrane.

Deficiencies in complement components, including C6, can lead to increased susceptibility to certain types of infections, as well as autoimmune disorders and other medical conditions.

Complement C3c is a protein component of the complement system, which is a part of the immune system that helps to clear pathogens and damaged cells from the body. Complement C3c is formed when the third component of the complement system (C3) is cleaved into two smaller proteins, C3a and C3b, during the complement activation process.

C3b can then be further cleaved into C3c and C3dg. C3c is a stable fragment that remains in the circulation and can be measured in blood tests as a marker of complement activation. It plays a role in the opsonization of pathogens, which means it coats them to make them more recognizable to immune cells, and helps to initiate the membrane attack complex (MAC), which forms a pore in the cell membrane of pathogens leading to their lysis or destruction.

Abnormal levels of C3c may indicate an underlying inflammatory or immune-mediated condition, such as infection, autoimmune disease, or cancer.

Complement C7 is a protein that plays a role in the complement system, which is a part of the immune system that helps to clear pathogens and damaged cells from the body. Specifically, C7 is a component of the membrane attack complex (MAC), which is a group of proteins that forms a pore in the membrane of target cells, leading to their lysis or destruction.

C7 is activated when it binds to the C5b-7 complex, which is formed by the cleavage of C5 and C6 by the C5 convertase. Once bound to the C5b-7 complex, C7 undergoes a conformational change that allows it to insert into the target cell membrane. This forms the basis for the formation of the MAC and subsequent lysis of the target cell.

Deficiencies in complement components, including C7, can lead to increased susceptibility to certain infections and autoimmune disorders. Additionally, abnormal regulation of the complement system has been implicated in a variety of diseases, including inflammatory and degenerative conditions.

The Mannose-Binding Lectin (MBL) pathway is a part of the complement system, which is a group of proteins that play a crucial role in the body's immune defense against infectious agents. The MBL pathway is an alternative activation pathway of the complement system, which can be initiated without the need for antibodies.

MBL is a protein found in blood plasma and other bodily fluids. It recognizes and binds to specific sugars (mannose and fucose) found on the surface of many microorganisms, including bacteria, viruses, fungi, and parasites. When MBL binds to these sugars, it triggers a series of proteolytic cleavage events that activate the complement components C4 and C2, forming the C3 convertase (C4b2a).

The C3 convertase then cleaves the complement component C3 into C3a and C3b. C3b can bind to the surface of microorganisms, leading to their opsonization (coating) and subsequent phagocytosis by immune cells. Additionally, C3b can also trigger the formation of the membrane attack complex (MAC), which creates a pore in the membrane of microorganisms, leading to their lysis and death.

Overall, the MBL pathway plays an essential role in innate immunity, providing a rapid and effective defense against invading microorganisms.

CD55, also known as Decay-accelerating factor (DAF), is a protein that acts as an inhibitor of the complement system, which is a part of the immune system. It prevents the formation of the membrane attack complex (MAC) on host cells and tissues, thereby protecting them from damage caused by the complement activation. CD55 is found on the surface of many types of cells in the body, including red blood cells, white blood cells, and cells lining the blood vessels.

As an antigen, CD55 is a molecule that can be recognized by the immune system and stimulate an immune response. However, unlike some other antigens, CD55 does not typically elicit a strong immune response because it is a self-antigen, meaning it is normally present in the body and should not be targeted by the immune system.

In certain medical conditions, such as autoimmune disorders or transplant rejection, the immune system may mistakenly attack cells expressing CD55. In these cases, measuring the levels of CD55 antigens can provide valuable diagnostic information and help guide treatment decisions.

The Complement C1 Inhibitor protein, also known as C1-INH, is a protein involved in the regulation of the complement system and the contact system, which are parts of the immune system. The complement system helps to eliminate pathogens (e.g., bacteria, viruses) from the body, while the contact system helps to regulate blood coagulation and inflammation.

C1-INH works by inhibiting the activation of C1, an enzyme complex that is the first component of the classical complement pathway. By inhibiting C1, C1-INH prevents the activation of downstream components of the complement system, thereby helping to regulate the immune response and prevent excessive inflammation.

Deficiencies or dysfunction in the C1-INH protein can lead to a group of genetic disorders known as C1 inhibitor deficiency disorders, which include hereditary angioedema (HAE) and acquired angioedema (AAE). These conditions are characterized by recurrent episodes of swelling in various parts of the body, such as the face, hands, feet, and airway, which can be painful and potentially life-threatening if they affect the airway.

Complement C8 is a protein component of the complement system, which is a part of the immune system that helps to eliminate pathogens and damaged cells from the body. Specifically, C8 is a part of the membrane attack complex (MAC), which forms a pore in the membrane of target cells, leading to their lysis or destruction.

C8 is composed of three subunits: alpha, beta, and gamma. It is activated when it binds to the complement component C5b67 complex on the surface of a target cell. Once activated, C8 undergoes a conformational change that allows it to insert into the target cell membrane and form a pore, which disrupts the cell's membrane integrity and can lead to its death.

Deficiencies in complement components, including C8, can make individuals more susceptible to certain infections and autoimmune diseases. Additionally, mutations in the genes encoding complement proteins have been associated with various inherited disorders, such as atypical hemolytic uremic syndrome (aHUS), which is characterized by thrombotic microangiopathy and kidney failure.

Factor I deficiency in turn leads to low levels of complement component 3 (C3), factor B, factor H and properdin in blood, due ... Complement factor I (factor I) is a protein of the complement system, first isolated in 1966 in guinea pig serum, that ... Loss of function mutations in the Complement Factor I gene lead to low levels of factor I which results in increased complement ... Complement factor I, also known as C3b/C4b inactivator, is a protein that in humans is encoded by the CFI gene. ...
... is a protein that in humans is encoded by the CFB gene. This gene encodes complement factor B, a component ... CFB complement factor B". Ambrus JL, Peters MG, Fauci AS, Brown EJ (March 1990). "The Ba fragment of complement factor B ... Christie DL, Gagnon J (January 1983). "Amino acid sequence of the Bb fragment from complement Factor B. Sequence of the major ... Upon activation of the alternative pathway, it is cleaved by complement factor D yielding the noncatalytic chain Ba and the ...
"The role of complement factor C3 in lipid metabolism". Molecular Immunology. 15th European Meeting on Complement in Human ... 12th European Meeting on Complement in Human Disease12th European Meeting on CHD12th European Meeting on Complement in Human ... that allows it to bind to a plasma protein called Factor B. This complex is then cleaved by Factor D, a serine protease, to ... Factor I, a serine protease activated by cofactors, can cleave and C3b and C4b, thus preventing convertase formation. C3 ...
Activated C3 can then interact with factor B. Factor B is then activated by factor D, to form Bb. The resultant complex, C3bBb ... "Interactions between human complement components factor H, factor I and C3b". The Biochemical Journal. 326 (2): 553-61. doi: ... Complement component 3 has been shown to interact with Factor H. Deficiencies in C3 lead to genetic infections, usually fatal ... Factor I is the protease cleaves C3b but requires a cofactor (e.g Factor H, CR1, MCP or C4BP) for activity. Several ...
This gene encodes the basic form of complement factor 4, part of the classical activation pathway. The protein is expressed as ... Complement component 4 Complement component 4A HLA A1-B8-DR3-DQ2 haplotype Complement system Complement deficiency ... Aoki H, Takizawa F, Tsuji S, Nagasawa S (Jul 2000). "Elongation factor-1alpha as a homologous complement activator of Jurkat ... Complement component 4B (Chido blood group) is a kind of the Complement component 4 protein that in humans is encoded by the ...
Decay Accelerating Factor, DAF (CD55) Protectin (CD59) Complement C3b/C4b Receptor 1, CR1 (CD35) Complement Regulator of the ... Complement control protein are proteins that interact with components of the complement system. The complement system is ... Complement proteins protect against malignant cells- both by direct complement attack and through initiation of Complement- ... factor H competes with factor B to bind C3b; if it manages to bind, then the convertase is not formed. Factor H can bind C3b ...
PSAP Complement component 4, partial deficiency of; 120790; C1NH Complement factor H deficiency; 609814; HF1 Complement factor ... GLA Factor V and factor VIII, combined deficiency of; 227300; MCFD2 Factor V deficiency; 227400; F5 Factor XI deficiency, ... F11 Factor XII deficiency; 234000; F12 Factor XIIIA deficiency; 613225; F13A1 Factor XIIIB deficiency; 613235; F13B Failure of ... LCAT Fletcher factor deficiency; 612423; KLKB1 Focal cortical dysplasia, Taylor balloon cell type; 607341; TSC1 Focal dermal ...
... complement subgroups factor a group into smaller pieces. As previously mentioned, complements need not exist. A p-complement is ... A Frobenius complement is a special type of complement in a Frobenius group. A complemented group is one where every subgroup ... if K is a complement of H, then H is a complement of K. Neither H nor K need be a normal subgroup of G. Complements need not ... That is, H could have two distinct complements K1 and K2 in G. If there are several complements of a normal subgroup, then they ...
"OMIM Entry - * 300383 - COMPLEMENT FACTOR PROPERDIN; CFP". www.omim.org. Retrieved 2022-03-24. editor., Leung, Donald Y. M., ... The gene responsible for the production of properdin, Complement Factor Properdin (CFP), lies on the X-chromosome at the ... Properdin deficiency is a rare X-linked disease in which properdin, an important complement factor responsible for the ... Pertaining to complement deficiencies, there is no cure and the treatments for complement deficiencies vary widely. The best ...
Like complement factor H, CFHR5 is able to bind to complement C3. A mutation in CHFR5 was found in patients with the disease ... "Entrez Gene: CFHR5 complement factor H-related 5". McRae JL, Duthy TG, Griggs KM, et al. (2005). "Human factor H-related ... 2006). "Variations in the complement regulatory genes factor H (CFH) and factor H related 5 (CFHR5) are associated with ... Complement factor H-related protein 5 is a protein that in humans is encoded by the CFHR5 gene. CFHR5 is structurally related ...
Diaz-Guillen MA, Rodriguez de Cordoba S, Heine-Suner D (Jul 1999). "A radiation hybrid map of complement factor H and factor H- ... CFHR4 complement factor H-related 4". Hageman GS, Hancox LS, Taiber AJ, et al. (2007). "Extended Haplotypes in the Complement ... Complement factor H-related protein 4 is a protein that in humans is encoded by the CFHR4 gene. GRCh38: Ensembl release 89: ... 2000). "Functional properties of complement factor H-related proteins FHR-3 and FHR-4: binding to the C3d region of C3b and ...
Complement factor H-related protein 2) at the PDBe-KB. Zipfel PF, Skerka C (1994). "Complement factor H and related proteins: ... Díaz-Guillén MA, Rodríguez de Córdoba S, Heine-Suñer D (1999). "A radiation hybrid map of complement factor H and factor H- ... "Two additional human serum proteins structurally related to complement factor H. Evidence for a family of factor H-related ... Complement factor H-related protein 2 is a protein that in humans is encoded by the CFHR2 gene. GRCh38: Ensembl release 89: ...
"Cellular adhesion mediated by factor J, a complement inhibitor. Evidence for nucleolin involvement". The Journal of Biological ... Nucleolin is also able to act as a transcriptional coactivator with Chicken Ovalbumin Upstream Promoter Transcription Factor II ...
... is produced when complement factor I cleaves C3b. Complement receptors on white blood cells are able to bind iC3b, so iC3b ... thus preventing amplification of the complement cascade through the alternative pathway. Complement factor I can further cleave ... iC3b is a protein fragment that is part of the complement system, a component of the vertebrate immune system. ... v t e (Complement system, All stub articles, Biochemistry stubs). ...
These SNPs were located in the gene encoding complement factor H, which was an unexpected finding in the research of ARMD. The ... April 2005). "Complement factor H polymorphism in age-related macular degeneration". Science. 308 (5720): 385-9. Bibcode: ... "Complement factor H variant increases the risk of age-related macular degeneration". Science. 308 (5720): 419-21. Bibcode: ... It has been identified different variants associated with transcription factor coding-genes, such as TBX3 and TBX5, NKX2-5 o ...
Wu LC, Morley BJ, Campbell RD (Jan 1987). "Cell-specific expression of the human complement protein factor B gene: evidence for ... the body signals the Complement system and the Complement component 2 protein attaches to Complement system 4 resulting in an ... It is also important to note that Complement component 2 deficiency can be caused by genetic and environmental factors. In ... Gagnon J (Sep 1984). "Structure and activation of complement components C2 and factor B". Philosophical Transactions of the ...
It can also be seen in systemic lupus erythematosus as a result of increased usage of complement factors due to the pathology ... The CH50 is testing the classical complement pathway in an individual thus requiring functioning C1-C9 factors. If an ... Total complement activity (TCA) refers to a series of tests that determine the functioning of the complement system in an ... One can interpret the CH50 value along with the individual's complement factor values to help determine the etiology. For ...
Complement factors are decreased in rheumatoid arthritis and lupus arthritis. Microscopic analysis of synovial fluid is ... Jay, GD; Britt, DE; Cha, CJ (March 2000). "Lubricin is a product of megakaryocyte stimulating factor gene expression by human ...
Markusen, James R. (May 1, 1983). "Factor movements and commodity trade as complements". Journal of International Economics. 14 ... Markusen, James R.; Venables, Anthony J. (November 1, 2007). "Interacting factor endowments and trade costs: A multi-country, ... Markusen's international trade and economics research has contributed to the identification of factors that influence trade ... Markusen's regional economics research has investigated how factors such as infrastructure and education, impact economic ...
Calippe, Bertrand; Guillonneau, Xavier; Sennlaub, Florian (March 2014). "Complement factor H and related proteins in age- ... A SNP in the F5 gene causes Factor V Leiden thrombophilia. rs3091244 is an example of a triallelic SNP in the CRP gene on human ... Other factors, like genetic recombination and mutation rate, can also determine SNP density. SNP density can be predicted by ... LD can be affected by two parameters (among other factors, such as population stratification): 1) The distance between the SNPs ...
Malhotra R, Ward M, Sim RB, Bird MI (July 1999). "Identification of human complement Factor H as a ligand for L-selectin". The ... The embryo secretes human chorionic gonadotropin (hCG), which downregulates anti-adhesion factor, MUC-1, located on the uterine ... Human sell consists of 10 exons and its transcription factor is FOXO 1, on the other hand the mouse sell gene is composed of 9 ... an adjacent epidermal growth factor-like domain, two to the consensus repeat units homologous to those found in C3/C4-binding ...
It is the first drug that selectively inhibits factor B, the active component of the complement's C3 and C5 convertases. In ... April 2019). "Small-molecule factor B inhibitor for the treatment of complement-mediated diseases". Proceedings of the National ... Iptacopan is also investigated as a drug in other complement-mediated diseases, like age-related macular degeneration and some ...
April 2005). "Complement factor H variant increases the risk of age-related macular degeneration". Science. 308 (5720): 419-21 ... Some of the factors that should be considered are the level of efficacy of various genetic tests in the general population, ... Combining molecular scale information with macro-scale clinical data, such as patients' tumor type and other risk factors, ... 2 July 2015). "Race/Ethnic Differences in the Associations of the Framingham Risk Factors with Carotid IMT and Cardiovascular ...
BCX9930, an oral Factor D inhibitor for the treatment of complement-mediated diseases. FDA has granted Fast Track designation ...
In the meantime, notebooks and small form factor desktop computers complement the range. The names of the devices borrow from ... Complementing Tuxedo OS, the company is working on tools to control hardware functions and improve usability. Licensed under ...
Opsonins include Mfge8, Gas6, Protein S, antibodies and complement factors C1q and C3b. Phagoptosis has multiple functions ... Pathogenic cells such as bacteria can be opsonised by antibodies or complement factors, enabling their phagocytosis and ...
1989). "20 KDa homologous restriction factor of complement resembles T cell activating protein". Biochem. Biophys. Res. Commun ... When complement activation leads to deposition of C5b678 on host cells, CD59 can prevent C9 from polymerizing and forming the ... Ninomiya H, Sims PJ (1992). "The human complement regulatory protein CD59 binds to the alpha-chain of C8 and to the "b"domain ... 1992). "Complement regulatory proteins at the feto-maternal interface during human placental development: distribution of CD59 ...
... factor H, factor HR1 or HR3, membrane cofactor protein, factor I, factor B, complement C3, and thrombomodulin). This results in ... The complement system activation may be due to mutations in the complement regulatory proteins (factor H, factor I, or membrane ... of complement can result from production of anti-factor H autoantibodies or from genetic mutations in any of several complement ... "Platelet-associated complement factor H in healthy persons and patients with atypical HUS". Blood. 114 (20): 4538-4545. doi: ...
Lee FJ, Moss J, Vaughan M (1992). "Human and Giardia ADP-ribosylation factors (ARFs) complement ARF function in Saccharomyces ... ADP-ribosylation factor 5 is a protein that in humans is encoded by the ARF5 gene. ADP-ribosylation factor 5 (ARF5) is a member ... Shin, O H; Exton J H (August 2001). "Differential binding of arfaptin 2/POR1 to ADP-ribosylation factors and Rac1". Biochem. ... Tsuchiya M, Price SR, Tsai SC, Moss J, Vaughan M (March 1991). "Molecular identification of ADP-ribosylation factor mRNAs and ...
"Entrez Gene: CFHR3 complement factor H-related 3". Zipfel PF, Skerka C (1994). "Complement factor H and related proteins: an ... Diaz-Guillen MA, Rodriguez de Cordoba S, Heine-Suner D (Jul 1999). "A radiation hybrid map of complement factor H and factor H- ... Complement factor H-related protein 3 is a protein that in humans is encoded by the CFHR3 gene. GRCh38: Ensembl release 89: ... 2000). "Complement factor H: sequence analysis of 221 kb of human genomic DNA containing the entire fH, fHR-1 and fHR-3 genes ...
Factor I deficiency in turn leads to low levels of complement component 3 (C3), factor B, factor H and properdin in blood, due ... Complement factor I (factor I) is a protein of the complement system, first isolated in 1966 in guinea pig serum, that ... Loss of function mutations in the Complement Factor I gene lead to low levels of factor I which results in increased complement ... Complement factor I, also known as C3b/C4b inactivator, is a protein that in humans is encoded by the CFI gene. ...
Complement factor I deficiency is a disorder that affects the immune system. Explore symptoms, inheritance, genetics of this ... or absent complement factor I. The lack (deficiency) of functional complement factor I protein allows uncontrolled activation ... medlineplus.gov/genetics/condition/complement-factor-i-deficiency/ Complement factor I deficiency. ... Complement factor I and several related proteins protect healthy cells by preventing activation of the complement system when ...
Rattus norvegicus complement factor H (Cfh), mRNA Rattus norvegicus complement factor H (Cfh), mRNA. gi,77861916,ref,NM_ ... Complement factor H regulates retinal development and its absence may establish a footprint for age related macular ... Complement factor H regulates retinal development and its absence may establish a footprint for age related macular ... The role of the microRNA-146a/complement factor H/interleukin-1β-mediated inflammatory loop circuit in the perpetuate ...
... Science. 2005 Apr 15;308(5720):419-21. doi: ... DNA resequencing of the complement factor H gene within this haplotype revealed a common coding variant, Y402H, that ...
Complement factor H. The complement system is a crucial component of the innate immunity against microbial infection. ... Complement factor H, a 155 kDaplasma glycoprotein, is an essential regulatory protein that plays a critical role in the ... Complement factor H has revealed an association with two different renal diseases, glomerulonephri-tisand atypical hemolytic ... Factor H binds to C3b, accelerates the decay of the alternative pathway C3-convertase and acts as a cofactor for the factor ...
... complement-mediated... (More). Complement factor B (FB) mutant variants are associated with excessive complement activation in ... atypical hemolytic uremic syndrome, C3 glomerulopathy, complement, danicopan, factor B, factor D. in Frontiers in Immunology. ... Factor D Inhibition Blocks Complement Activation Induced by Mutant Factor B Associated With Atypical Hemolytic Uremic Syndrome ... Complement factor B (FB) mutant variants are associated with excessive complement activation in kidney diseases such as ...
title = "Complement C4 Deficiency - A Plausible Risk Factor for Non-Tuberculous Mycobacteria (NTM) Infection in Apparently ... T1 - Complement C4 Deficiency - A Plausible Risk Factor for Non-Tuberculous Mycobacteria (NTM) Infection in Apparently ... Complement C4 Deficiency - A Plausible Risk Factor for Non-Tuberculous Mycobacteria (NTM) Infection in Apparently ... Complement C4 Deficiency - A Plausible Risk Factor for Non-Tuberculous Mycobacteria (NTM) Infection in Apparently ...
Events / Evening Meeting / Insights from Reliability-Based Design to Complement Load and Resistance Factor Design Approach ... Insights from Reliability-Based Design to Complement Load and Resistance Factor Design Approach. ... "Insights from Reliability-Based Design to Complement Load and Resistance Factor Design Approach," by B.K. Low in the November ...
Dive into the research topics of Functional anatomy of complement Factor H. Together they form a unique fingerprint. ...
... the complement system reacts promptly to threat (AP). Protective membrane-bound and soluble r.. ... Complement Factor H: Function and Dysfunction Due to the constant monitoring of its alternate channel, the complement system ... Pathogenic microorganisms, on the other hand, frequently resist complement assault and so escape destruction. Complement factor ... Binding sites, especially for complement receptor (CR3), malondialdehyde (MDA)-modified proteins, and apolipoprotein E (apoE), ...
Background Effective regulation of complement activation may be crucial to preserving complement function during ARDS. Factor H ... Factor H preserves alternative complement function during ARDS linked to improved survival. William Bain, Mohammadreza Tabary, ... Factor H preserves alternative complement function during ARDS linked to improved survival ... Factor H preserves alternative complement function during ARDS linked to improved survival ...
Variation registry for Complement factor I deficiency Select database by name. ADAbase. AICDAbase. AIREbase. AK2base. AP3B1base ...
... of complement factor H. The factor H deficiency was defined by undetectable complement hemolytic activity by the classic (CH50 ... 2006) noted that a defect in complement factor H results in continuous activation of the alternative complement pathway and ... Decreased levels of serum C3 and factor B but normal levels of serum C4 and factor I were found; factor H was undetectable by ... 1987) studied a family in which 3 female sibs had undetectable levels of factor H and C3 nephritic factor, low levels of factor ...
Complement receptor 1 (CR1) has factor H-like activity, permitting factor I to cleave C3b. Membrane cofactor protein also has ... Ehrlich and Morgan termed this factor complement. The complement system as understood today is a multimolecular system composed ... Factor H competes with factor B for binding to C3b and displaces Bb from C3bBb. It accelerates the inactivation of C3b by ... Here, C3b binds to factor B that is cleaved by factor D to Bb. C3bBb complex then acts as the C3 convertase and generates more ...
Learn more about an association of rare mutation in the complement factor I gene and numerous episodes of recurrent aseptic ... The complement regulatory factor I (CFI) is a two-chain serine protease and an endogenous inhibitor of the classical and ... Complement Factor I Gene Variant as a Treatable Cause of Recurrent Aseptic Neutrophilic Meningitis. Neurol Neuroimmunol ... He was found to have a rare heterozygous mutation in the complement factor I gene (CFI) that was not previously associated with ...
Complement C3 nephritic factor. Category. Immunology Test background. A proportion of patients with membranoproliferative ...
... complement factor H [CFH], C4b binding protein, and complement factor I [CFI]) [37, 38]. Defective regulation of the complement ... 4. PE and Complement Factors. The complement system, composed of over 30 proteins that act in concert to protect the host ... 2. Angiogenic Factors and PE. Angiogenic factors and their receptors are important regulators of placental vascular development ... A. Sambola, J. Osende, J. Hathcock et al., "Role of risk factors in the modulation of tissue factor activity and blood ...
How endothelial cells protect themselves from complement by expressing decay-accelerating factor (DAF). *Frances Williams1 ... Williams, F. How endothelial cells protect themselves from complement by expressing decay-accelerating factor (DAF). Arthritis ... How endothelial cells protect themselves from complement by expressing decay-accelerating factor (DAF) ... To test the hypothesis that inflammatory cytokines and complement(C) MACs play a role in the expression of DAF, CD59 and MCP, ...
de Vries, B, Matthijsen, RA, Wolfs, TGAM, van Bijnen, AA, Heeringa, P & Buurman, WA 2003, Inhibition of complement factor C5 ... T1 - Inhibition of complement factor C5 protects against renal ischemia-reperfusion injury: inhibition of late apoptosis and ... N2 - Inhibition of complement factor C5 protects against renal ischemia-reperfusion injury: inhibition of late apoptosis and ... AB - Inhibition of complement factor C5 protects against renal ischemia-reperfusion injury: inhibition of late apoptosis and ...
You are here: Home1 / Protein & Peptides2 / Recombinant Mouse Adipsin / Complement Factor D / CFD Protein (His Tag... ... Complement Factor D / CFD Protein (His Tag). ... Recombinant Mouse Adipsin / Complement Factor D / CFD Protein ( ...
Expression of human complement regulating factor (hCRF) in porcine organs prevents hyperacute rejection of these organs after ... Expression of human complement regulating factor (hCRF) in porcine organs prevents hyperacute rejection of these organs after ... Expression of human complement regulating factor (hCRF) in porcine organs prevents hyperacute rejection of these organs after ... Expression of human complement regulating factor (hCRF) in porcine organs prevents hyperacute rejection of these organs after ...
Complement factor H,Complement factor H. C,. H [auth G]. 383. Homo sapiens. Mutation(s): 0 Gene Names: CFH, HF, HF1, HF2. ... Complement factor I. D,. I [auth H]. 321. Homo sapiens. Mutation(s): 0 Gene Names: CFI, IF. EC: 3.4.21.45. ... Complement factor I. E [auth I],. J. 244. Homo sapiens. Mutation(s): 0 Gene Names: CFI, IF. EC: 3.4.21.45. ... Complement C3. A,. F [auth E]. 645. Homo sapiens. Mutation(s): 0 Gene Names: C3, CPAMD1. ...
... recognizes human complement factor H which exists in 2 forms. The most common form, of 150 kDa, and the les… ... strong,Mouse anti Human Complement Factor H antibody, clone 028B-244.2.10X (10-10),/strong, ... Mouse anti Human Complement Factor H antibody, clone 028B-244.2.10X (10-10) recognizes human complement factor H which exists ... Complement factor H functions as a cofactor in the inactivation of C3b by factor I. It makes C3b susceptible to cleavage by ...
Identification of complement factor 5 as a susceptibility locus for experimental allergic asthma. Nature Immunology. 2000 Sep;1 ... Identification of complement factor 5 as a susceptibility locus for experimental allergic asthma. In: Nature Immunology. 2000 ... Identification of complement factor 5 as a susceptibility locus for experimental allergic asthma. / Karp, Christopher L.; Grupe ... title = "Identification of complement factor 5 as a susceptibility locus for experimental allergic asthma", ...
Further insights into modulation of complement activation by the factor H-related family of proteins ... Further insights into modulation of complement activation by the factor H-related family of proteins ...
We now show that complement factor H-related protein 1 (FHR-1) and factor H-like protein 1 (FHL-1), proteins of the FH protein ... Interaction of Shiga toxin 2 with complement regulators of the factor H protein family.. Poolpol K, Orth-Höller D, Speth C, ... Stx2 was shown to activate complement via the alternative pathway, to bind factor H (FH) at short consensus repeats (SCRs) 6-8 ... Interaction of Shiga toxin 2 with complement regulators of the factor H protein family. Mol Immunol 58(1), 77-84. ...
Adipocytes have high levels of many components of the complement system. These components are involved in antimicrobial ... Complement factor D (adipsin) levels are elevated in acquired partial lipodystrophy (Barraquer-Simons syndrome). Int. J. Mol. ... Complement-mediated adipocyte lysis by nephritic factor sera. J. Exp. Med. 177, 1827-1831 (1993). ... Kruglikov, I.L., Scherer, P.E. Control of adipose tissue cellularity by the terminal complement cascade. Nat Rev Endocrinol 19 ...
Complement factor C5a exerts an anti-inflammatory effect in acute pancreatitis and associated lung injury. American Journal of ... Complement factor C5a exerts an anti-inflammatory effect in acute pancreatitis and associated lung injury. In: American Journal ... Complement factor C5a exerts an anti-inflammatory effect in acute pancreatitis and associated lung injury. / Bhatia, Madhav; ... Bhatia, M, Saluja, AK, Singh, VP, Frossard, JL, Lee, HS, Bhagat, L, Gerard, C & Steer, ML 2001, Complement factor C5a exerts ...
Primary: complement. Persistent complement, properdin, or Factor B deficiency. None. Pneumococcal. Meningococcal. Hib (children ... Persons with functional or anatomic asplenia (including sickle cell disease), HIV infection and persistent complement component ... Persons with functional or anatomic asplenia (including sickle cell disease) and persistent complement component deficiency ( ... Other immunosuppressive medications include human immune mediators like interleukins and colony-stimulating factors, immune ...
... transforming growth factor-beta1, tumor necrosis factor-alpha, or interferon-gamma. C3 and factor B proteins were measured in ... In skin the keratinocyte is the major cell type, it is known to produce two soluble complement components, C3 and factor B. In ... Synthesis of complement components C3 and factor B in human keratinocytes is differentially regulated by cytokines. ... Tumor necrosis factor-alpha induced production of C3 and interferon-gamma induced production of factor B were inhibited by ...
  • Complement factor I and several related proteins protect healthy cells by preventing activation of the complement system when it is not needed. (medlineplus.gov)
  • Binding sites, especially for complement receptor (CR3), malondialdehyde (MDA)-modified proteins, and apolipoprotein E (apoE), are dispersed throughout its 20 CCP modules (CCPs), also known as short consensus repeats, to facilitate additional 'non-canonical' FH activities. (imedpub.com)
  • The complement system as understood today is a multimolecular system composed of more than 32 proteins and consisting of serum proteins, serosal proteins, and cell membrane receptors that bind to complement fragments. (medscape.com)
  • The complement system consists of 7 serum and 9 membrane regulatory proteins, 1 serosal regulatory protein, and 8 cell membrane receptors that bind complement fragments. (medscape.com)
  • The complement regulatory factor I (CFI) is a two-chain serine protease and an endogenous inhibitor of the classical and alternative complement pathways by cleaving C3b and C4b in the presence of cofactor proteins. (discovermednews.com)
  • Cell surface proteins have evolved which prevent EC damage by the cytotoxic defence system, decay-accelerating factor (DAF), protectin (CD59) and membrane cofactor protein (MCP). (biomedcentral.com)
  • We now show that complement factor H-related protein 1 (FHR-1) and factor H-like protein 1 (FHL-1), proteins of the FH protein family that show amino acid sequence and regulatory function similarities with FH, also bind to Stx2. (leibniz-hki.de)
  • C3 and factor B proteins were measured in culture supernatant by enzyme-linked immunosorbent assay and C3 and factor B transcripts in harvested cells by reverse transcriptase - polymerase chain reaction . (bvsalud.org)
  • Cytokine induced upregulation of C3 and factor B proteins was always associated with the upregulation of levels of C3 and factor B mRNA . (bvsalud.org)
  • This binding is dependent on the expression of proteins termed complement-regulator acquiring surface proteins (CRASPs). (ox.ac.uk)
  • thus, PIGA mutations lead to a deficiency of GPI-anchored proteins, such as complement decay-accelerating factor (also known as CD55) and CD59 glycoprotein (CD59), which are both complement inhibitors. (medscape.com)
  • The key factors in clot formation are the chemical and physical nature of the surfaces and their interactions with the blood components, such as platelets and plasma proteins. (springer.com)
  • Genes that encode the proteins of complement components or their isotypes are distributed throughout different chromosomes, with 19 genes comprising 3 significant complement gene clusters in the human genome. (medscape.com)
  • The important components of this system are various cell membrane-associated proteins such as complement receptor 1 (CR1), complement receptor 2 (CR2), and decay accelerating factor (DAF). (medscape.com)
  • for example, the proteins factor H and factor I inhibit the formation of the enzyme C3 convertase of the alternative pathway. (medscape.com)
  • Complement factor I, also known as C3b/C4b inactivator, is a protein that in humans is encoded by the CFI gene. (wikipedia.org)
  • Complement factor I (factor I) is a protein of the complement system, first isolated in 1966 in guinea pig serum, that regulates complement activation by cleaving cell-bound or fluid phase C3b and C4b. (wikipedia.org)
  • Then, factor I is cleaved by furin to yield the mature factor I protein, which is a disulfide-linked dimer of heavy chain (residues 19-335, 51 kDalton) and light chain (residues 340-583, 37 kDalton). (wikipedia.org)
  • the heavy chain plays an inhibitory role in maintaining the enzyme inactive until it meets the complex formed by the substrate (either C3b or C4b) and a cofactor protein (Factor H, C4b-binding protein, complement receptor 1, and membrane cofactor protein). (wikipedia.org)
  • This gene provides instructions for making a protein called complement factor I. This protein helps regulate a part of the body's immune response known as the complement system . (medlineplus.gov)
  • Mutations in the CFI gene that cause complement factor I deficiency result in abnormal, nonfunctional, or absent complement factor I. The lack (deficiency) of functional complement factor I protein allows uncontrolled activation of the complement system. (medlineplus.gov)
  • The unregulated activity of the complement system decreases blood levels of another complement protein called C3, reducing the immune system's ability to fight infections. (medlineplus.gov)
  • See the reference protein sequence for complement factor H precursor (NP_569093.2). (nih.gov)
  • Complement factor H, a 155 kDaplasma glycoprotein, is an essential regulatory protein that plays a critical role in the homeostasis of the complement system in plasma and in the protection of bystander host cells and tissues from damage by complement activation. (biovendor.com)
  • In addition, factor H has multiple physiological activities acts as an extracellularmatrix component, binds to cellular receptors of the integrintype, and interacts with a wide selection of ligands, such as the C-reactive protein, thrombospondin, bone sialoprotein, osteopontin, and heparin. (biovendor.com)
  • Complement factor H is a soluble AP suppressor that recognizes self-surfaces on autologous surfaces, either directly via particular glycosaminoglycan and sialic acid or indirectly via C-reactive protein (CRP), and operates in fluid phase. (imedpub.com)
  • 1987) studied a family in which 3 female sibs had undetectable levels of factor H and C3 nephritic factor, low levels of factor B, C3, and C5 (see 120500), and normal levels of C4-binding protein (120830), factor I (217030), and classic pathway factors. (findzebra.com)
  • Interaction of Shiga toxin 2 with complement regulators of the factor H protein family. (leibniz-hki.de)
  • Poolpol K, Orth-Höller D, Speth C, Zipfel PF, Skerka C, de Córdoba SR, Brockmeyer J, Bielaszewska M, Würzner R (2014) Interaction of Shiga toxin 2 with complement regulators of the factor H protein family. (leibniz-hki.de)
  • Complement factor H (CFH), consisting of 20 domains called complement control protein (CCP1-20), downregulates the AP as a cofactor for mediating C3 inactivation by complement factor I. However, anomalies related to CFH are known to cause excessive complement activation and cytotoxicity. (elsevierpure.com)
  • Structure-function mapping of BbCRASP-1, the key complement factor H and FHL-1 binding protein of Borrelia burgdorferi. (ox.ac.uk)
  • Serum-resistant B. burgdorferi strains bind complement factor H (FH) and FH-like protein 1 (FHL-1) on the spirochaete surface. (ox.ac.uk)
  • In an individual with the sporadic/relapsing form of the disease we have found a mutation comprising a deletion, subsequent frame shift and premature stop codon leading to half normal levels of serum factor H. In one of the three families there is a point mutation in exon 20 causing an arginine to glycine change, which is likely to alter structure and hence function of the factor H protein. (nih.gov)
  • Factor H is a major plasma protein that plays a critical regulatory role in the alternative pathway of complement activation. (nih.gov)
  • Eculizumab (Soliris) and ravulizumab-cwvz (Ultomiris) are inhibitors that work to block complement protein C5. (webmd.com)
  • There's another complement protein called C6. (webmd.com)
  • Protein expression is influenced by many factors that may vary between experiments or laboratories. (genscript.com)
  • These bacteria use the surface protein Usp2 to capture and incapacitate the major complement factor C3. (lu.se)
  • 1986) reported a consanguineous Algerian family in which 2 brothers had early-onset glomerulonephritis with C3 deposits and low levels (less than 10% of normal) of complement factor H . The factor H deficiency was defined by undetectable complement hemolytic activity by the classic (CH50) and alternate (AP50) pathways, and low levels of C3 and factor B (138470). (findzebra.com)
  • Activation of the complement pathways. (medscape.com)
  • This prevents these components of the classical and of alternative complement pathways from forming a positive feedback loop. (bio-rad-antibodies.com)
  • The complement cascade consists of 3 separate pathways that converge in a final common pathway. (medscape.com)
  • Complement pathways and deficiencies. (medscape.com)
  • Welch (2002) discussed the role of complement in renal disease. (findzebra.com)
  • The role of complement in modulating susceptibility to asthma highlights the importance of immunoregulatory events at the interface of innate and adaptive immunity in disease pathogenesis. (johnshopkins.edu)
  • In conclusion, multiple interactions of key complement inhibitors FH, FHR-1 and FHL-1 with Stx2 corroborate our hypothesis of a direct role of complement in EHEC-associated HUS. (leibniz-hki.de)
  • Cases of complement deficiency have helped defined the role of complement in host defense. (medscape.com)
  • The complement decay-accelerating factor CD55 exhibited the greatest reduction in cell surface levels during infection. (imperial.ac.uk)
  • Expression of human complement regulating factor (hCRF) in porcine organs prevents hyperacute rejection of these organs after xenotransplantation to nonhuman primates. (elsevierpure.com)
  • Mouse anti Human Complement Factor H antibody, clone 028B-244.2.10X (10-10) recognizes human complement factor H which exists in 2 forms. (bio-rad-antibodies.com)
  • Another important mechanism by which bacteria resist human complement is the production of proteases that efficiently degrade complement components. (lu.se)
  • Atypical hemolytic uremic syndrome is caused by complement overactivation. (wikipedia.org)
  • Complement factor B (FB) mutant variants are associated with excessive complement activation in kidney diseases such as atypical hemolytic uremic syndrome (aHUS), C3 glomerulopathy and membranoproliferative glomerulonephritis (MPGN). (lu.se)
  • Atypical hemolytic uremic syndrome (aHUS) is a disease associated with dysregulation of the immune complement system, especially of the alternative pathway (AP). (elsevierpure.com)
  • Dive into the research topics of 'Functional anatomy of complement Factor H'. Together they form a unique fingerprint. (ed.ac.uk)
  • Conventional protease inhibitors do not completely inactivate Factor I but they can do so if the enzyme is pre-incubated with its substrate: this supports the proposed rearrangement of the molecule upon binding to the substrate. (wikipedia.org)
  • These two latter pathogenic mechanisms are the target of novel strategies of anti-complement treatments, which can be split into terminal and proximal complement inhibitors. (frontiersin.org)
  • Many novel terminal complement inhibitors are now in clinical development: they all target C5 (as eculizumab), potentially paralleling the efficacy and safety profile of eculizumab. (frontiersin.org)
  • Indeed, proximal inhibitors are designed to interfere with early phases of complement activation, eventually preventing C3-mediated extravascular hemolysis in addition to intravascular hemolysis. (frontiersin.org)
  • Indeed, we envision a new scenario of therapeutic complement inhibition, where proximal inhibitors (either anti-C3, anti-FD or anti-FB) may prove effective for the treatment of PNH, either in monotherapy or in combination with anti-C5 agents, eventually leading to drastic improvement of hematological response. (frontiersin.org)
  • 2006) summarized features of MPGN relevant to the complement cascade. (findzebra.com)
  • More than 80% of patients with MPGN II are positive for serum C3 nephritic factor (C3NeF), an autoantibody directed against C3bBb, the convertase of the alternative pathway of the complement cascade. (findzebra.com)
  • The complement system functions as an interactive sequence, with one reaction leading to another in the form of a cascade. (medscape.com)
  • Mutations in the CFI gene result in an inability to control the complement cascade appropriately. (discovermednews.com)
  • How the immune response can activate the cascade process is still unknown but it is proposed to act in synergy with additional exacerbating factors such as predisposing maternal and ambient factors [ 12 ]. (hindawi.com)
  • mouse homolog is a regulatory serine proteinase of the complement cascade that cleaves C3b and C4b and inactivates them [RGD, Feb 2006]. (genscript.com)
  • The effects of settled grain dust on the human serum complement cascade were investigated. (cdc.gov)
  • Deficiencies in the complement cascade can lead to overwhelming infection and sepsis. (medscape.com)
  • New studies point to the complex interplay between the complement cascade and adaptive immune response, and complement is also being studied in association with ischemic injury as a target of therapy. (medscape.com)
  • Complement factor D (adipsin) levels are elevated in acquired partial lipodystrophy (Barraquer-Simons syndrome). (nature.com)
  • abstract = "Inhibition of complement factor C5 protects against renal ischemia-reperfusion injury: inhibition of late apoptosis and inflammation.De Vries B, Matthijsen RA, Wolfs TG, Van Bijnen AA, Heeringa P, Buurman WA.Department of General Surgery, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, Maastricht, The Netherlands.BACKGROUND: Complement has been implicated in the pathophysiology of renal ischemia-reperfusion (I/R) injury. (maastrichtuniversity.nl)
  • CONCLUSIONS: Renal I/R is followed by activation of the complement system and intrarenal deposition of C3 and MAC. (maastrichtuniversity.nl)
  • To study the effect of MAC on HMEC expression of DAF, EC monolayers were opsonised with IgG2a anti-endoglin monoclonal antibody, thus optimising complement fixation ability. (biomedcentral.com)
  • Mice were control treated or treated with BB5.1, a monoclonal antibody that prevents cleavage of complement factor C5, thereby preventing C5a generation and formation of the membrane attack complex (MAC). (maastrichtuniversity.nl)
  • Lectins activate the lectin pathway in a manner similar to the antibody interaction with complement in the classical pathway. (medscape.com)
  • Complement factor I deficiency is a disorder that affects the immune system. (medlineplus.gov)
  • Immune complement and coagulation dysfunction in adverse outcomes of SARS-CoV-2 infection. (nih.gov)
  • The trouble in PNH comes from part of your immune system called the complement system. (webmd.com)
  • The complement system is part of the innate immune system. (medscape.com)
  • In addition to playing an important role in host defense against infection, the complement system is a mediator in both the pathogenesis and prevention of immune complex diseases, such as systemic lupus erythematosus (SLE). (medscape.com)
  • Factor H binds to C3b, accelerates the decay of the alternative pathway C3-convertase and acts as a cofactor for the factor Imediated proteolyticinac-tivation of C3b. (biovendor.com)
  • Factor H (FH) is the primary negative regulator of the alternative pathway (AP) of complement. (ersjournals.com)
  • Laboratory features usually include decreased serum levels of factor H , complement component C3 (120700), and a decrease in other alternative pathway components, indicating activation of the alternative complement pathway. (findzebra.com)
  • Depending on the nature of complement activators, the classic pathway, the alternative pathway, or the more recently discovered lectin pathway is activated predominantly to produce C3 convertase. (medscape.com)
  • Binding of factor H to C3b increases its inactivation by factor I. Properdin stabilizes it, preventing its inactivation by factors H and I. The alternate pathway does not result in a truly nonspecific activation of complement because it requires specific types of compounds for activation. (medscape.com)
  • To test the hypothesis that inflammatory cytokines and complement(C) MACs play a role in the expression of DAF, CD59 and MCP, and to investigate the intracellular signalling pathway involved in DAF expression. (biomedcentral.com)
  • It is important in regulating the complement pathway, preventing unnecessary inflammation which can damage the host tissue. (bio-rad-antibodies.com)
  • Stx2 was shown to activate complement via the alternative pathway, to bind factor H (FH) at short consensus repeats (SCRs) 6-8 and 18-20 and to delay and reduce FH cofactor activity on the cell surface. (leibniz-hki.de)
  • It is widely accepted that members of the complement pathway are expressed at high levels in white adipose tissue (WAT). (nature.com)
  • Cellular lysis is counteracted by different cellular defence mechanisms that control this 'tug-of-war' behaviour of the complement system: it can be kept in check or let loose and activate a cell death pathway. (nature.com)
  • Upregulation of early and downregulation of terminal pathway complement genes in subcutaneous adipose tissue and adipocytes in acquired obesity. (nature.com)
  • and regulation of complement activation, alternative pathway. (jax.org)
  • In vitro activation of the alternative pathway of complement by settled grain dust. (cdc.gov)
  • The factor I heavy chain has four domains: an FI membrane attack complex (FIMAC) domain, CD5 domain, and low density lipoprotein receptor 1 and 2 (LDLr1 and LDLr2) domains. (wikipedia.org)
  • Similarly, sEng is a truncated form of receptor for two subtypes of transforming growth factor beta (TGF β ) specifically, TGF β 1 and TGF β 2 which are highly expressed by vascular endothelial cells and syncytiotrophoblasts. (hindawi.com)
  • Factor-B conversion and reductions in hemolytic complement consumption were dose related. (cdc.gov)
  • Background Effective regulation of complement activation may be crucial to preserving complement function during ARDS. (ersjournals.com)
  • Cellular membrane type-1 matrix metalloproteinase (MT1-MMP) cleaves C3b, an essential component of the complement system. (nature.com)
  • Mutagenesis was performed to study the effect of factor D (FD) inhibition on C3 convertase-induced FB cleavage, complement-mediated. (lu.se)
  • These results suggest that FD inhibition can effectively block complement overactivation induced by FB gain-of-function mutations. (lu.se)
  • Furthermore, we examined the effect of inhibition of complement-factor C5 on renal I/R injury. (maastrichtuniversity.nl)
  • Anti-complement Treatment for Paroxysmal Nocturnal Hemoglobinuria: Time for Proximal Complement Inhibition? (frontiersin.org)
  • At the moment there are three strategies of proximal complement inhibition: anti-C3 agents, anti-factor D agents and anti-factor B agents. (frontiersin.org)
  • Preliminary data clearly demonstrate that proximal complement inhibition is pharmacologically feasible and apparently safe, and may drastically improve the hematological response to complement inhibition in PNH. (frontiersin.org)
  • The role of the microRNA-146a/complement factor H/interleukin-1β-mediated inflammatory loop circuit in the perpetuate inflammation of chronic temporal lobe epilepsy. (nih.gov)
  • Complement activation plays a crucial role in the regulation of inflammation and late apoptosis. (maastrichtuniversity.nl)
  • The complement system plays an important part in host defense and inflammation . (bvsalud.org)
  • 4 , 6 - 9 Several factors, including inflammation, oxidative stress, and dyslipidemia, are considered decisive for the progression of atherosclerosis in ESRD. (lww.com)
  • at the same time, the inflammation promoted by complement activation can result in cellular damage when not kept in check. (medscape.com)
  • Another, danicopan, is a factor D inhibitor. (webmd.com)
  • Fabhalta (iptacopan) is a first-in-class, complement factor B inhibitor. (drugs.com)
  • We showed that one common strategy is to bind complement inhibitor C4BP, which leads to decreased opsonisation of bacteria with C3b impairing phagocytosis and allowing bacterial survival. (lu.se)
  • Enables complement component C3b binding activity and heparin binding activity. (jax.org)
  • Loss of function mutations in the Complement Factor I gene lead to low levels of factor I which results in increased complement activity. (wikipedia.org)
  • Complement factor I deficiency is caused by mutations in the CFI gene. (medlineplus.gov)
  • Subsequent mutation analysis of the factor H gene has revealed two mutations in patients with HUS. (nih.gov)
  • Human keratinocytes were cultured in the presence of supernatant of activated peripheral blood mononuclear cells , interleukin-1alpha , interleukin-2 , interleukin-6 , transforming growth factor-beta1 , tumor necrosis factor-alpha , or interferon-gamma . (bvsalud.org)
  • Tumor necrosis factor-alpha induced production of C3 and interferon-gamma induced production of factor B were inhibited by cycloheximide . (bvsalud.org)
  • In 1 family, of Polish origin, a teenaged male had vasculitis, thrombocytopenia, proteinuria, and depressed levels of serum factor H and complement component C3. (findzebra.com)
  • The index case had depressed serum factors H and B levels and IgA nephropathy (161950) which progressed to renal failure. (findzebra.com)
  • The most widely studied serum markers for PE, to date, are vascular endothelial growth factor (VEGF) and placental growth factor (PlGF). (hindawi.com)
  • Factor H is secreted by the liver into the blood serum. (bio-rad-antibodies.com)
  • CspA-mediated binding of human factor H inhibits complement deposition and confers serum resistance in Borrelia burgdorferi. (ouhsc.edu)
  • An intricate system regulates complement activity. (medscape.com)
  • The complement system is a crucial component of the innate immunity against microbial infection. (biovendor.com)
  • Due to the constant monitoring of its alternate channel, the complement system reacts promptly to threat (AP). (imedpub.com)
  • The complement system labels microbes and host debris for clearance. (rcsb.org)
  • The complement system has recently been found to be involved in the pathogenesis of EHEC-associated HUS. (leibniz-hki.de)
  • Adipocytes have high levels of many components of the complement system. (nature.com)
  • Up-regulation of the complement system in subcutaneous adipocytes from nonobese, hypertriglyceridemic subjects is associated with adipocyte insulin resistance. (nature.com)
  • Researchers are also looking at medicines that work against other players in the complement system. (webmd.com)
  • The complement system plays an important part in defense against pyogenic organisms. (medscape.com)
  • These findings underscore the duality of the complement system. (medscape.com)
  • Knowledge about the complement system is expanding. (medscape.com)
  • Although the complement system is part of the body's innate, relatively nonspecific defense against pathogens, its role is hardly primitive or easily understood. (medscape.com)
  • Using microarray analysis of pulmonary gene expression and single nucleotide polymorphism-based genotyping, combined with quantitative trait locus analysis, we identified the gene encoding complement factor 5 (C5) as a susceptibility locus for allergen-induced airway hyperresponsiveness in a murine model of asthma. (johnshopkins.edu)
  • BACKGROUND: Complement has been implicated in the pathophysiology of renal ischemia-reperfusion (I/R) injury. (maastrichtuniversity.nl)
  • How do endothelial cells (ECs) protect themselves against damage by complement, particularly when they are present at the interface between blood and inflamed tissue? (biomedcentral.com)
  • DAF prevents the formation and accelerates the decay of complement 3 (C3) convertases, MCP binds to C3b and C4b promoting their degradation and CD59 inhibits the membrane-attack complex (MAC). (biomedcentral.com)
  • Complement factor H functions as a cofactor in the inactivation of C3b by factor I. It makes C3b susceptible to cleavage by factor I, resulting in iC3b. (bio-rad-antibodies.com)
  • Angiogenic factors and their receptors are important regulators of placental vascular development [ 13 ]. (hindawi.com)
  • This work demonstrates that pathogens interact with complement regulators in ways that are distinct from the mechanisms used by the host and are thus obvious targets for drug design. (ox.ac.uk)
  • Dysregulated factor I activity has clinical implications. (wikipedia.org)
  • Clinical significance of complement deficiencies. (medlineplus.gov)
  • This in turn results in an exponential production of multiple factors such as cytokines and growth factors leading to the clinical manifestations of PE [ 11 ]. (hindawi.com)
  • Some new clinical entities are linked with partial complement defects. (medscape.com)
  • This article outlines some of the disease states associated with complement deficiencies and their clinical implications. (medscape.com)
  • Factor I deficiency in turn leads to low levels of complement component 3 (C3), factor B, factor H and properdin in blood, due to unregulated activation of C3 convertase, and to low levels of IgG, due to loss of iC3b and C3dg production. (wikipedia.org)
  • In the first phase, a series of specific interactions leads to formation of intrinsic complement proteinase, termed C3 convertase. (medscape.com)
  • Factor H also inhibits the formation of the C3bBb complex (C3 convertase) and increases the rate of dissociation of both C3 convertase and the (C3b)NBB complex (C5 convertase). (bio-rad-antibodies.com)
  • Grumach AS, Leitao MF, Arruk VG, Kirschfink M, Condino-Neto A. Recurrent infections in partial complement factor I deficiency: evaluation of three generations of a Brazilian family. (medlineplus.gov)
  • Rattus norvegicus complement factor I (Cfi), mRNA. (genscript.com)
  • Complement factor H has revealed an association with two different renal diseases, glomerulonephri-tisand atypical hemolytic uremicsyndrome (aHUS). (biovendor.com)
  • Patients with aHUS are currently treated with eculizumab while there is no specific treatment for other complement-mediated renal diseases. (lu.se)
  • Synthesis of complement components C3 and factor B in human keratinocytes is differentially regulated by cytokines. (bvsalud.org)
  • In skin the keratinocyte is the major cell type, it is known to produce two soluble complement components, C3 and factor B . In this study we investigated the regulation of synthesis of these components in foreskin keratinocytes by cytokines . (bvsalud.org)
  • In conclusion, synthesis of C3 and factor B in keratinocytes is regulated by some cytokines , known to be produced by inflammatory cells and keratinocytes . (bvsalud.org)
  • He was found to have a rare heterozygous mutation in the complement factor I gene (CFI) that was not previously associated with neurologic manifestations. (discovermednews.com)
  • These findings confirmed an association between a rare mutation in the complement factor I gene and numerous episodes of recurrent aseptic meningitis. (discovermednews.com)
  • As a first line of defense against pathogens and a mediator between innate and adaptive immunity, complement is a particular focus of evasion strategies developed by pathogens. (lu.se)
  • The factor I light chain contains only the serine protease domain. (wikipedia.org)
  • The authors then performed a complement analysis, which revealed that component concentrations and factor levels were normal. (discovermednews.com)
  • In addition to the following diseases, low factor I is associated with recurrent bacterial infections in children. (wikipedia.org)
  • Complement factor H deficiency (CFHD) can manifest as several different phenotypes, including asymptomatic, recurrent bacterial infections, and renal failure. (findzebra.com)
  • 1 It is a multifactorial disease with several identified genetic and environmental risk factors, including age, smoking, body mass index, hypertension, and others. (dovepress.com)
  • Genetic, behavioral, and sociodemographic risk factors for second eye progression in age-related macular degeneration. (genscript.com)
  • [ 3 ] A registry of complement deficiencies has been established as a means to promote joint projects on treatment and prevention of diseases associated with defective complement function. (medscape.com)
  • Complement deficiencies are said to comprise between 1 and 10% of all primary immunodeficiencies. (medscape.com)
  • Deficiencies in complement predispose patients to infection via 2 mechanisms: (1) ineffective opsonization and (2) defects in lytic activity (defects in MAC). (medscape.com)
  • Specific complement deficiencies are also associated with an increased risk of developing autoimmune disease, such as SLE. (medscape.com)
  • The term "nocturnal" refers to the belief that hemolysis is triggered by acidosis during sleep and activates complement to hemolyze an unprotected and abnormal RBC membrane. (medscape.com)
  • Here, C3b binds to factor B that is cleaved by factor D to Bb. (medscape.com)
  • Complement factor C5a acting via C5a receptors (C5aR) is recognized as an anaphylotoxin and chemoattractant that exerts proinflammatory effects in many pathological states. (elsevierpure.com)
  • Factor I is a glycoprotein heterodimer consisting of a disulfide linked heavy chain and light chain. (wikipedia.org)