Complement Pathway, Classical: 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.Complement C3: 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 C4: 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.Complement Activation: 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.Complement C1q: 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.Complement C3-C5 Convertases: 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 C2: 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).Complement C4b: 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).Complement C3b: 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.Complement Pathway, Alternative: 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.Complement C4a: The smaller fragment formed when complement C4 is cleaved by COMPLEMENT C1S. It is an anaphylatoxin that causes symptoms of immediate hypersensitivity (HYPERSENSITIVITY, IMMEDIATE) but its activity is weaker than that of COMPLEMENT C3A or COMPLEMENT C5A.Complement System Proteins: 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).Complement C5: 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.Complement Activating Enzymes: 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.Complement C3a: 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.Complement Inactivator Proteins: 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.Complement C1: 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.Proprotein Convertase 2: A serine endopeptidase that has specificity for cleavage at ARGININE. It cleaves a variety of prohormones including PRO-OPIOMELANOCORTIN, proluteinizing-hormone-releasing hormone, proenkephalins, prodynorphin, and PROINSULIN.Complement C5a: 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.Proprotein Convertase 1: A CALCIUM-dependent endopeptidase that has specificity for cleavage at ARGININE that is near paired basic residues. It cleaves a variety of prohormones including PRO-OPIOMELANOCORTIN; PRORENIN; proenkephalins; prodynorphin; prosomatostatin; and PROINSULIN.Complement Factor B: 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.Complement C1s: A 77-kDa subcomponent of complement C1, encoded by gene C1S, is a SERINE PROTEASE existing as a proenzyme (homodimer) in the intact complement C1 complex. Upon the binding of COMPLEMENT C1Q to antibodies, the activated COMPLEMENT C1R cleaves C1s into two chains, A (heavy) and B (light, the serine protease), linked by disulfide bonds yielding the active C1s. The activated C1s, in turn, cleaves COMPLEMENT C2 and COMPLEMENT C4 to form C4b2a (CLASSICAL C3 CONVERTASE).Complement C6: 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.Complement C5 Convertase, Classical Pathway: A serine protease that cleaves multiple COMPLEMENT 5 into COMPLEMENT 5A (anaphylatoxin) and COMPLEMENT 5B in the CLASSICAL COMPLEMENT ACTIVATION PATHWAY. It is a complex of CLASSICAL PATHWAY C3 CONVERTASE (C4b2a) with an additional COMPLEMENT C3B, or C4b2a3b.Complement C3d: 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).Complement C3c: 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.Receptors, Complement: Molecules on the surface of some B-lymphocytes and macrophages, that recognize and combine with the C3b, C3d, C1q, and C4b components of complement.Complement C9: 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.Complement C1r: A 80-kDa subcomponent of complement C1, existing as a SERINE PROTEASE proenzyme in the intact complement C1 complex. When COMPLEMENT C1Q is bound to antibodies, the changed tertiary structure causes autolytic activation of complement C1r which is cleaved into two chains, A (heavy) and B (light, the serine protease), connected by disulfide bonds. The activated C1r serine protease, in turn, activates COMPLEMENT C1S proenzyme by cleaving the Arg426-Ile427 bond. No fragment is released when either C1r or C1s is cleaved.Complement C3 Convertase, Classical Pathway: A serine protease that cleaves multiple COMPLEMENT 3 into COMPLEMENT 3A (anaphylatoxin) and COMPLEMENT 3B in the CLASSICAL COMPLEMENT ACTIVATION PATHWAY. It is a complex of COMPLEMENT 4B and COMPLEMENT 2A (C4b2a).Proprotein Convertase 5: A serine endopeptidase found primarily in the EXTRACELLULAR MATRIX. It has specificity for cleavage of a variety of substrates including PRORENIN, pro-membrane type-1 matrix metalloproteinase, and NEURAL CELL ADHESION MOLECULE L1.Complement Membrane Attack Complex: 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.Proprotein Convertases: Proteolytic enzymes that are involved in the conversion of protein precursors such as peptide prohormones into PEPTIDE HORMONES. Some are ENDOPEPTIDASES, some are EXOPEPTIDASES.Properdin: 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.Complement C2a: The COOH-terminal fragment of COMPLEMENT 2, released by the action of activated COMPLEMENT C1S. It is a SERINE PROTEASE. C2a combines with COMPLEMENT C4B to form C4b2a (CLASSICAL PATHWAY C3 CONVERTASE) and subsequent C4b2a3b (CLASSICAL PATHWAY C5 CONVERTASE).Complement Factor D: 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.Complement C7: 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 C2b: The N-terminal fragment of COMPLEMENT 2, released by the action of activated COMPLEMENT C1S.Complement C3 Convertase, Alternative Pathway: 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.Complement C5b: The larger fragment generated from the cleavage of C5 by C5 CONVERTASE that yields COMPLEMENT C5A and C5b (beta chain + alpha' chain, the residual alpha chain, bound by disulfide bond). C5b remains bound to the membrane and initiates the spontaneous assembly of the late complement components to form C5b-8-poly-C9, the MEMBRANE ATTACK COMPLEX.Complement C1 Inactivator Proteins: Serum proteins that inhibit, antagonize, or inactivate COMPLEMENT C1 or its subunits.Complement Factor H: 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).Complement C4b-Binding Protein: A serum protein that regulates the CLASSICAL COMPLEMENT ACTIVATION PATHWAY. It binds as a cofactor to COMPLEMENT FACTOR I which then hydrolyzes the COMPLEMENT C4B in the CLASSICAL PATHWAY C3 CONVERTASE (C4bC2a).Receptors, Complement 3b: 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.Complement Hemolytic Activity Assay: 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.Complement C3b Inactivator Proteins: 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.Hemolysis: The destruction of ERYTHROCYTES by many different causal agents such as antibodies, bacteria, chemicals, temperature, and changes in tonicity.Complement Factor I: 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.Complement C3 Nephritic Factor: An IgG autoantibody against the ALTERNATIVE PATHWAY C3 CONVERTASE, found in serum of patients with MESANGIOCAPILLARY GLOMERULONEPHRITIS. The binding of this autoantibody to C3bBb stabilizes the enzyme thus reduces the actions of C3b inactivators (COMPLEMENT FACTOR H; COMPLEMENT FACTOR I). This abnormally stabilized enzyme induces a continuous COMPLEMENT ACTIVATION and generation of C3b thereby promoting the assembly of MEMBRANE ATTACK COMPLEX and cytolysis.Complement C3-C5 Convertases, Classical Pathway: Important enzymes in the CLASSICAL COMPLEMENT ACTIVATION PATHWAY. They cleave COMPLEMENT C3 and COMPLEMENT C5.Subtilisins: A family of SERINE ENDOPEPTIDASES isolated from Bacillus subtilis. EC 3.4.21.-Furin: A proprotein convertase with specificity for the proproteins of PROALBUMIN; COMPLEMENT 3C; and VON WILLEBRAND FACTOR. It has specificity for cleavage near paired ARGININE residues that are separated by two amino acids.Complement Inactivating Agents: Compounds that negatively regulate the cascade process of COMPLEMENT ACTIVATION. Uncontrolled complement activation and resulting cell lysis is potentially dangerous for the host.Antigens, CD55: 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.Complement C8: 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.Complement C1 Inhibitor Protein: 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.Opsonin Proteins: Proteins that bind to particles and cells to increase susceptibility to PHAGOCYTOSIS, especially ANTIBODIES bound to EPITOPES that attach to FC RECEPTORS. COMPLEMENT C3B may also participate.Antigen-Antibody Complex: The complex formed by the binding of antigen and antibody molecules. The deposition of large antigen-antibody complexes leading to tissue damage causes IMMUNE COMPLEX DISEASES.Complement Pathway, Mannose-Binding Lectin: 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.Immunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.Receptor, Anaphylatoxin C5a: A G-protein-coupled receptor that signals an increase in intracellular calcium in response to the potent ANAPHYLATOXIN peptide COMPLEMENT C5A.Blood Bactericidal Activity: The natural bactericidal property of BLOOD due to normally occurring antibacterial substances such as beta lysin, leukin, etc. This activity needs to be distinguished from the bactericidal activity contained in a patient's serum as a result of antimicrobial therapy, which is measured by a SERUM BACTERICIDAL TEST.Neuroendocrine Secretory Protein 7B2: An acidic protein found in the NEUROENDOCRINE SYSTEM that functions as a molecular chaperone for PROPROTEIN CONVERTASE 2.Complement Fixation Tests: Serologic tests based on inactivation of complement by the antigen-antibody complex (stage 1). Binding of free complement can be visualized by addition of a second antigen-antibody system such as red cells and appropriate red cell antibody (hemolysin) requiring complement for its completion (stage 2). Failure of the red cells to lyse indicates that a specific antigen-antibody reaction has taken place in stage 1. If red cells lyse, free complement is present indicating no antigen-antibody reaction occurred in stage 1.Receptors, Complement 3d: Molecular sites on or in B-lymphocytes, follicular dendritic cells, lymphoid cells, and epithelial cells that recognize and combine with COMPLEMENT C3D. Human complement receptor 2 (CR2) serves as a receptor for both C3dg and the gp350/220 glycoprotein of HERPESVIRUS 4, HUMAN, and binds the monoclonal antibody OKB7, which blocks binding of both ligands to the receptor.Serine Endopeptidases: Any member of the group of ENDOPEPTIDASES containing at the active site a serine residue involved in catalysis.Antigens, CD59: Small glycoproteins found on both hematopoietic and non-hematopoietic cells. CD59 restricts the cytolytic activity of homologous complement by binding to C8 and C9 and blocking the assembly of the membrane attack complex. (From Barclay et al., The Leukocyte Antigen FactsBook, 1993, p234)Antigens, CD46: A ubiquitously expressed complement receptor that binds COMPLEMENT C3B and COMPLEMENT C4B and serves as a cofactor for their inactivation. CD46 also interacts with a wide variety of pathogens and mediates immune response.Anaphylatoxins: Serum peptides derived from certain cleaved COMPLEMENT PROTEINS during COMPLEMENT ACTIVATION. They induce smooth MUSCLE CONTRACTION; mast cell HISTAMINE RELEASE; PLATELET AGGREGATION; and act as mediators of the local inflammatory process. The order of anaphylatoxin activity from the strongest to the weakest is C5a, C3a, C4a, and C5a des-arginine.Molecular Sequence Data: 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.Collectins: A class of C-type lectins that target the carbohydrate structures found on invading pathogens. Binding of collectins to microorganisms results in their agglutination and enhanced clearance. Collectins form trimers that may assemble into larger oligomers. Each collectin polypeptide chain consists of four regions: a relatively short N-terminal region, a collagen-like region, an alpha-helical coiled-coil region, and carbohydrate-binding region.Mannose-Binding Lectin: A specific mannose-binding member of the collectin family of lectins. It binds to carbohydrate groups on invading pathogens and plays a key role in the MANNOSE-BINDING LECTIN COMPLEMENT PATHWAY.Phagocytosis: The engulfing and degradation of microorganisms; other cells that are dead, dying, or pathogenic; and foreign particles by phagocytic cells (PHAGOCYTES).Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Amino Acid Sequence: 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.Immunoglobulin M: A class of immunoglobulin bearing mu chains (IMMUNOGLOBULIN MU-CHAINS). IgM can fix COMPLEMENT. The name comes from its high molecular weight and originally being called a macroglobulin.Carboxypeptidase H: A ZINC-containing exopeptidase primarily found in SECRETORY VESICLES of endocrine and neuroendocrine cells. It catalyzes the cleavage of C-terminal ARGININE or LYSINE residues from polypeptides and is active in processing precursors of PEPTIDE HORMONES and other bioactive peptides.Cobra Venoms: 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.ZymosanMannose-Binding Protein-Associated Serine Proteases: Serum serine proteases which participate in COMPLEMENT ACTIVATION. They are activated when complexed with the MANNOSE-BINDING LECTIN, therefore also known as Mannose-binding protein-Associated Serine Proteases (MASPs). They cleave COMPLEMENT C4 and COMPLEMENT C2 to form C4b2a, the CLASSICAL PATHWAY C3 CONVERTASE.Erythrocytes: Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.Cryoglobulins: Abnormal immunoglobulins, especially IGG or IGM, that precipitate spontaneously when SERUM is cooled below 37 degrees Celsius. It is characteristic of CRYOGLOBULINEMIA.Lupus Erythematosus, Systemic: A chronic, relapsing, inflammatory, and often febrile multisystemic disorder of connective tissue, characterized principally by involvement of the skin, joints, kidneys, and serosal membranes. It is of unknown etiology, but is thought to represent a failure of the regulatory mechanisms of the autoimmune system. The disease is marked by a wide range of system dysfunctions, an elevated erythrocyte sedimentation rate, and the formation of LE cells in the blood or bone marrow.Mannans: Polysaccharides consisting of mannose units.Recombinant Proteins: Proteins prepared by recombinant DNA technology.Glomerulonephritis: Inflammation of the renal glomeruli (KIDNEY GLOMERULUS) that can be classified by the type of glomerular injuries including antibody deposition, complement activation, cellular proliferation, and glomerulosclerosis. These structural and functional abnormalities usually lead to HEMATURIA; PROTEINURIA; HYPERTENSION; and RENAL INSUFFICIENCY.Dose-Response Relationship, Immunologic: A specific immune response elicited by a specific dose of an immunologically active substance or cell in an organism, tissue, or cell.Mice, Inbred C57BLComplement C5 Convertase, Alternative Pathway: A serine protease that cleaves multiple COMPLEMENT C5 into COMPLEMENT C5A (anaphylatoxin) and COMPLEMENT C5B in the ALTERNATIVE COMPLEMENT ACTIVATION PATHWAY. It is the complex of ALTERNATIVE PATHWAY C3 CONVERTASE (C3bBb) with an additional COMPLEMENT C3B, or C3bBb3b.Peptide Fragments: Partial proteins formed by partial hydrolysis of complete proteins or generated through PROTEIN ENGINEERING techniques.Enzyme-Linked Immunosorbent Assay: An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Guinea Pigs: A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.Neutrophils: Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes.Protein PrecursorsRabbits: The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.Sheep: Any of the ruminant mammals with curved horns in the genus Ovis, family Bovidae. They possess lachrymal grooves and interdigital glands, which are absent in GOATS.Antibodies, Monoclonal: Antibodies produced by a single clone of cells.Kinetics: The rate dynamics in chemical or physical systems.Protein Structure, Tertiary: The level of protein structure in which combinations of secondary protein structures (alpha helices, beta sheets, loop regions, and motifs) pack together to form folded shapes called domains. Disulfide bridges between cysteines in two different parts of the polypeptide chain along with other interactions between the chains play a role in the formation and stabilization of tertiary structure. Small proteins usually consist of only one domain but larger proteins may contain a number of domains connected by segments of polypeptide chain which lack regular secondary structure.Steroid 21-Hydroxylase: An adrenal microsomal cytochrome P450 enzyme that catalyzes the 21-hydroxylation of steroids in the presence of molecular oxygen and NADPH-FERRIHEMOPROTEIN REDUCTASE. This enzyme, encoded by CYP21 gene, converts progesterones to precursors of adrenal steroid hormones (CORTICOSTERONE; HYDROCORTISONE). Defects in CYP21 cause congenital adrenal hyperplasia (ADRENAL HYPERPLASIA, CONGENITAL).Cell Line: Established cell cultures that have the potential to propagate indefinitely.Immunoelectrophoresis: A technique that combines protein electrophoresis and double immunodiffusion. In this procedure proteins are first separated by gel electrophoresis (usually agarose), then made visible by immunodiffusion of specific antibodies. A distinct elliptical precipitin arc results for each protein detectable by the antisera.Complement C3-C5 Convertases, Alternative Pathway: Important enzymes in the ALTERNATIVE COMPLEMENT ACTIVATION PATHWAY. They cleave COMPLEMENT C3 and COMPLEMENT C5.Blood Proteins: Proteins that are present in blood serum, including SERUM ALBUMIN; BLOOD COAGULATION FACTORS; and many other types of proteins.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Surface Plasmon Resonance: A biosensing technique in which biomolecules capable of binding to specific analytes or ligands are first immobilized on one side of a metallic film. Light is then focused on the opposite side of the film to excite the surface plasmons, that is, the oscillations of free electrons propagating along the film's surface. The refractive index of light reflecting off this surface is measured. When the immobilized biomolecules are bound by their ligands, an alteration in surface plasmons on the opposite side of the film is created which is directly proportional to the change in bound, or adsorbed, mass. Binding is measured by changes in the refractive index. The technique is used to study biomolecular interactions, such as antigen-antibody binding.Glycoproteins: Conjugated protein-carbohydrate compounds including mucins, mucoid, and amyloid glycoproteins.Immunoglobulins: Multi-subunit proteins which function in IMMUNITY. They are produced by B LYMPHOCYTES from the IMMUNOGLOBULIN GENES. They are comprised of two heavy (IMMUNOGLOBULIN HEAVY CHAINS) and two light chains (IMMUNOGLOBULIN LIGHT CHAINS) with additional ancillary polypeptide chains depending on their isoforms. The variety of isoforms include monomeric or polymeric forms, and transmembrane forms (B-CELL ANTIGEN RECEPTORS) or secreted forms (ANTIBODIES). They are divided by the amino acid sequence of their heavy chains into five classes (IMMUNOGLOBULIN A; IMMUNOGLOBULIN D; IMMUNOGLOBULIN E; IMMUNOGLOBULIN G; IMMUNOGLOBULIN M) and various subclasses.Eosinophil-Derived Neurotoxin: A 19-kDa cationic peptide found in EOSINOPHIL granules. Eosinophil-derived neurotoxin is a RIBONUCLEASE and may play a role as an endogenous antiviral agent.Electrophoresis, Polyacrylamide Gel: Electrophoresis in which a polyacrylamide gel is used as the diffusion medium.Carrier Proteins: Transport proteins that carry specific substances in the blood or across cell membranes.Antibodies: Immunoglobulin molecules having a specific amino acid sequence by virtue of which they interact only with the ANTIGEN (or a very similar shape) that induced their synthesis in cells of the lymphoid series (especially PLASMA CELLS).Base Sequence: The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Autoantibodies: Antibodies that react with self-antigens (AUTOANTIGENS) of the organism that produced them.Antibodies, Bacterial: Immunoglobulins produced in a response to BACTERIAL ANTIGENS.Lectins: Proteins that share the common characteristic of binding to carbohydrates. Some ANTIBODIES and carbohydrate-metabolizing proteins (ENZYMES) also bind to carbohydrates, however they are not considered lectins. PLANT LECTINS are carbohydrate-binding proteins that have been primarily identified by their hemagglutinating activity (HEMAGGLUTININS). However, a variety of lectins occur in animal species where they serve diverse array of functions through specific carbohydrate recognition.Protein Processing, Post-Translational: Any of various enzymatically catalyzed post-translational modifications of PEPTIDES or PROTEINS in the cell of origin. These modifications include carboxylation; HYDROXYLATION; ACETYLATION; PHOSPHORYLATION; METHYLATION; GLYCOSYLATION; ubiquitination; oxidation; proteolysis; and crosslinking and result in changes in molecular weight and electrophoretic motility.Enzyme Precursors: Physiologically inactive substances that can be converted to active enzymes.Aspartic Acid Endopeptidases: A sub-subclass of endopeptidases that depend on an ASPARTIC ACID residue for their activity.Pituitary Hormones: Hormones secreted by the PITUITARY GLAND including those from the anterior lobe (adenohypophysis), the posterior lobe (neurohypophysis), and the ill-defined intermediate lobe. Structurally, they include small peptides, proteins, and glycoproteins. They are under the regulation of neural signals (NEUROTRANSMITTERS) or neuroendocrine signals (HYPOTHALAMIC HORMONES) from the hypothalamus as well as feedback from their targets such as ADRENAL CORTEX HORMONES; ANDROGENS; ESTROGENS.Edetic Acid: A chelating agent that sequesters a variety of polyvalent cations such as CALCIUM. It is used in pharmaceutical manufacturing and as a food additive.Molecular Weight: The sum of the weight of all the atoms in a molecule.Proglucagon: The common precursor polypeptide of pancreatic GLUCAGON and intestinal GLUCAGON-LIKE PEPTIDES. Proglucagon is the 158-amino acid segment of preproglucagon without the N-terminal signal sequence. Proglucagon is expressed in the PANCREAS; INTESTINES; and the CENTRAL NERVOUS SYSTEM. Posttranslational processing of proglucagon is tissue-specific yielding numerous bioactive peptides.Eosinophil Peroxidase: A 66-kDa peroxidase found in EOSINOPHIL granules. Eosinophil peroxidase is a cationic protein with a pI of 10.8 and is comprised of a heavy chain subunit and a light chain subunit. It possesses cytotoxic activity towards BACTERIA and other organisms, which is attributed to its peroxidase activity.Pro-Opiomelanocortin: A 30-kDa protein synthesized primarily in the ANTERIOR PITUITARY GLAND and the HYPOTHALAMUS. It is also found in the skin and other peripheral tissues. Depending on species and tissues, POMC is cleaved by PROHORMONE CONVERTASES yielding various active peptides including ACTH; BETA-LIPOTROPIN; ENDORPHINS; MELANOCYTE-STIMULATING HORMONES; and others (GAMMA-LPH; CORTICOTROPIN-LIKE INTERMEDIATE LOBE PEPTIDE; N-terminal peptide of POMC or NPP).Lipopolysaccharides: Lipid-containing polysaccharides which are endotoxins and important group-specific antigens. They are often derived from the cell wall of gram-negative bacteria and induce immunoglobulin secretion. The lipopolysaccharide molecule consists of three parts: LIPID A, core polysaccharide, and O-specific chains (O ANTIGENS). When derived from Escherichia coli, lipopolysaccharides serve as polyclonal B-cell mitogens commonly used in laboratory immunology. (From Dorland, 28th ed)Glomerulonephritis, Membranoproliferative: Chronic glomerulonephritis characterized histologically by proliferation of MESANGIAL CELLS, increase in the MESANGIAL EXTRACELLULAR MATRIX, and a thickening of the glomerular capillary walls. This may appear as a primary disorder or secondary to other diseases including infections and autoimmune disease SYSTEMIC LUPUS ERYTHEMATOSUS. Various subtypes are classified by their abnormal ultrastructures and immune deposits. Hypocomplementemia is a characteristic feature of all types of MPGN.RNA, Messenger: RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm.Streptococcus pneumoniae: A gram-positive organism found in the upper respiratory tract, inflammatory exudates, and various body fluids of normal and/or diseased humans and, rarely, domestic animals.Bacterial Outer Membrane Proteins: Proteins isolated from the outer membrane of Gram-negative bacteria.EsterasesComplement C5a, des-Arginine: A derivative of complement C5a, generated when the carboxy-terminal ARGININE is removed by CARBOXYPEPTIDASE B present in normal human serum. C5a des-Arg shows complete loss of spasmogenic activity though it retains some chemotactic ability (CHEMOATTRACTANTS).Species Specificity: The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.Egtazic Acid: A chelating agent relatively more specific for calcium and less toxic than EDETIC ACID.Macrophage-1 Antigen: An adhesion-promoting leukocyte surface membrane heterodimer. The alpha subunit consists of the CD11b ANTIGEN and the beta subunit the CD18 ANTIGEN. The antigen, which is an integrin, functions both as a receptor for complement 3 and in cell-cell and cell-substrate adhesive interactions.Metalloendopeptidases: ENDOPEPTIDASES which use a metal such as ZINC in the catalytic mechanism.Chromatography, Gel: Chromatography on non-ionic gels without regard to the mechanism of solute discrimination.C-Reactive Protein: A plasma protein that circulates in increased amounts during inflammation and after tissue damage.Sequence Homology, Amino Acid: The degree of similarity between sequences of amino acids. This information is useful for the analyzing genetic relatedness of proteins and species.Cloning, Molecular: The insertion of recombinant DNA molecules from prokaryotic and/or eukaryotic sources into a replicating vehicle, such as a plasmid or virus vector, and the introduction of the resultant hybrid molecules into recipient cells without altering the viability of those cells.Immune Sera: Serum that contains antibodies. It is obtained from an animal that has been immunized either by ANTIGEN injection or infection with microorganisms containing the antigen.Bacterial Proteins: Proteins found in any species of bacterium.Blotting, Western: Identification of proteins or peptides that have been electrophoretically separated by blot transferring from the electrophoresis gel to strips of nitrocellulose paper, followed by labeling with antibody probes.Kidney Glomerulus: A cluster of convoluted capillaries beginning at each nephric tubule in the kidney and held together by connective tissue.Serum: The clear portion of BLOOD that is left after BLOOD COAGULATION to remove BLOOD CELLS and clotting proteins.Binding, Competitive: The interaction of two or more substrates or ligands with the same binding site. The displacement of one by the other is used in quantitative and selective affinity measurements.Glicentin: A 69-amino acid peptide derived from the N-terminal of PROGLUCAGON. It is mainly produced by the INTESTINAL L CELLS. Further processing of glicentin yield a 30-amino acid N-terminal peptide (glicentin-related polypeptide) and a 37-amino acid peptide OXYNTOMODULIN. Both glicentin and oxyntomodulin can reduce digestive secretions and delay gastric emptying.Antigens, Bacterial: Substances elaborated by bacteria that have antigenic activity.Carboxypeptidases: Enzymes that act at a free C-terminus of a polypeptide to liberate a single amino acid residue.Schistosoma: A genus of trematode flukes belonging to the family Schistosomatidae. There are over a dozen species. These parasites are found in man and other mammals. Snails are the intermediate hosts.Genetic Complementation Test: A test used to determine whether or not complementation (compensation in the form of dominance) will occur in a cell with a given mutant phenotype when another mutant genome, encoding the same mutant phenotype, is introduced into that cell.Subtilisin: A serine endopeptidase isolated from Bacillus subtilis. It hydrolyzes proteins with broad specificity for peptide bonds, and a preference for a large uncharged residue in P1. It also hydrolyzes peptide amides. (From Enzyme Nomenclature, 1992) EC 126.96.36.199.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Flow Cytometry: Technique using an instrument system for making, processing, and displaying one or more measurements on individual cells obtained from a cell suspension. Cells are usually stained with one or more fluorescent dyes specific to cell components of interest, e.g., DNA, and fluorescence of each cell is measured as it rapidly transverses the excitation beam (laser or mercury arc lamp). Fluorescence provides a quantitative measure of various biochemical and biophysical properties of the cell, as well as a basis for cell sorting. Other measurable optical parameters include light absorption and light scattering, the latter being applicable to the measurement of cell size, shape, density, granularity, and stain uptake.CHO Cells: CELL LINE derived from the ovary of the Chinese hamster, Cricetulus griseus (CRICETULUS). The species is a favorite for cytogenetic studies because of its small chromosome number. The cell line has provided model systems for the study of genetic alterations in cultured mammalian cells.Arteriolosclerosis: Thickening of the walls of small ARTERIES or ARTERIOLES due to cell proliferation or HYALINE deposition.Transfection: The uptake of naked or purified DNA by CELLS, usually meaning the process as it occurs in eukaryotic cells. It is analogous to bacterial transformation (TRANSFORMATION, BACTERIAL) and both are routinely employed in GENE TRANSFER TECHNIQUES.Major Histocompatibility Complex: The genetic region which contains the loci of genes which determine the structure of the serologically defined (SD) and lymphocyte-defined (LD) TRANSPLANTATION ANTIGENS, genes which control the structure of the IMMUNE RESPONSE-ASSOCIATED ANTIGENS, HUMAN; the IMMUNE RESPONSE GENES which control the ability of an animal to respond immunologically to antigenic stimuli, and genes which determine the structure and/or level of the first four components of complement.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Cricetinae: A subfamily in the family MURIDAE, comprising the hamsters. Four of the more common genera are Cricetus, CRICETULUS; MESOCRICETUS; and PHODOPUS.Receptors, LDL: Receptors on the plasma membrane of nonhepatic cells that specifically bind LDL. The receptors are localized in specialized regions called coated pits. Hypercholesteremia is caused by an allelic genetic defect of three types: 1, receptors do not bind to LDL; 2, there is reduced binding of LDL; and 3, there is normal binding but no internalization of LDL. In consequence, entry of cholesterol esters into the cell is impaired and the intracellular feedback by cholesterol on 3-hydroxy-3-methylglutaryl CoA reductase is lacking.Hemoglobinuria, Paroxysmal: A condition characterized by the recurrence of HEMOGLOBINURIA caused by intravascular HEMOLYSIS. In cases occurring upon cold exposure (paroxysmal cold hemoglobinuria), usually after infections, there is a circulating antibody which is also a cold hemolysin. In cases occurring during or after sleep (paroxysmal nocturnal hemoglobinuria), the clonal hematopoietic stem cells exhibit a global deficiency of cell membrane proteins.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Membrane Proteins: Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.Mice, Inbred BALB CPolymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Cytotoxicity, Immunologic: The phenomenon of target cell destruction by immunologically active effector cells. It may be brought about directly by sensitized T-lymphocytes or by lymphoid or myeloid "killer" cells, or it may be mediated by cytotoxic antibody, cytotoxic factor released by lymphoid cells, or complement.DNA Primers: Short sequences (generally about 10 base pairs) of DNA that are complementary to sequences of messenger RNA and allow reverse transcriptases to start copying the adjacent sequences of mRNA. Primers are used extensively in genetic and molecular biology techniques.Signal Transduction: The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Gene Expression Regulation: Any of the processes by which nuclear, cytoplasmic, or intercellular factors influence the differential control (induction or repression) of gene action at the level of transcription or translation.ADAM Proteins: A family of membrane-anchored glycoproteins that contain a disintegrin and metalloprotease domain. They are responsible for the proteolytic cleavage of many transmembrane proteins and the release of their extracellular domain.Macrophages: The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood MONOCYTES. Main types are PERITONEAL MACROPHAGES; ALVEOLAR MACROPHAGES; HISTIOCYTES; KUPFFER CELLS of the liver; and OSTEOCLASTS. They may further differentiate within chronic inflammatory lesions to EPITHELIOID CELLS or may fuse to form FOREIGN BODY GIANT CELLS or LANGHANS GIANT CELLS. (from The Dictionary of Cell Biology, Lackie and Dow, 3rd ed.)Immunity, Innate: The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from the presence of naturally occurring ANTI-INFECTIVE AGENTS, constitutional factors such as BODY TEMPERATURE and immediate acting immune cells such as NATURAL KILLER CELLS.Gene Expression: The phenotypic manifestation of a gene or genes by the processes of GENETIC TRANSCRIPTION and GENETIC TRANSLATION.Membrane Glycoproteins: Glycoproteins found on the membrane or surface of cells.DNA, Complementary: Single-stranded complementary DNA synthesized from an RNA template by the action of RNA-dependent DNA polymerase. cDNA (i.e., complementary DNA, not circular DNA, not C-DNA) is used in a variety of molecular cloning experiments as well as serving as a specific hybridization probe.DNA: A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine).Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Immunohistochemistry: Histochemical localization of immunoreactive substances using labeled antibodies as reagents.Oxyntomodulin: A 37-amino acid peptide derived from the C-terminal of GLICENTIN. It is mainly produced by the INTESTINAL L CELLS. Oxyntomodulin can reduce digestive secretions, delay gastric emptying, and reduced food intake.Proteolysis: Cleavage of proteins into smaller peptides or amino acids either by PROTEASES or non-enzymatically (e.g., Hydrolysis). It does not include Protein Processing, Post-Translational.Antigens, CD: Differentiation antigens residing on mammalian leukocytes. CD stands for cluster of differentiation, which refers to groups of monoclonal antibodies that show similar reactivity with certain subpopulations of antigens of a particular lineage or differentiation stage. The subpopulations of antigens are also known by the same CD designation.Fibrinogen: Plasma glycoprotein clotted by thrombin, composed of a dimer of three non-identical pairs of polypeptide chains (alpha, beta, gamma) held together by disulfide bonds. Fibrinogen clotting is a sol-gel change involving complex molecular arrangements: whereas fibrinogen is cleaved by thrombin to form polypeptides A and B, the proteolytic action of other enzymes yields different fibrinogen degradation products.Alleles: Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.Kidney: Body organ that filters blood for the secretion of URINE and that regulates ion concentrations.Cell Membrane: The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.alpha 1-Antitrypsin: Plasma glycoprotein member of the serpin superfamily which inhibits TRYPSIN; NEUTROPHIL ELASTASE; and other PROTEOLYTIC ENZYMES.Haptoglobins: Plasma glycoproteins that form a stable complex with hemoglobin to aid the recycling of heme iron. They are encoded in man by a gene on the short arm of chromosome 16.Substrate Specificity: A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.Protease Inhibitors: Compounds which inhibit or antagonize biosynthesis or actions of proteases (ENDOPEPTIDASES).Models, Molecular: Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.Isoflurophate: A di-isopropyl-fluorophosphate which is an irreversible cholinesterase inhibitor used to investigate the NERVOUS SYSTEM.Sequence Homology, Nucleic Acid: The sequential correspondence of nucleotides in one nucleic acid molecule with those of another nucleic acid molecule. Sequence homology is an indication of the genetic relatedness of different organisms and gene function.Hydrolysis: The process of cleaving a chemical compound by the addition of a molecule of water.Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Peptides, Cyclic: Peptides whose amino and carboxy ends are linked together with a peptide bond forming a circular chain. Some of them are ANTI-INFECTIVE AGENTS. Some of them are biosynthesized non-ribosomally (PEPTIDE BIOSYNTHESIS, NON-RIBOSOMAL).Blotting, Northern: Detection of RNA that has been electrophoretically separated and immobilized by blotting on nitrocellulose or other type of paper or nylon membrane followed by hybridization with labeled NUCLEIC ACID PROBES.
Autoantibody stabilization of the classical pathway C3 convertase leading to C3 deficiency and Neisserial sepsis: C4 nephritic factor revisited. (1/1)(+info)
No data available that match "complement c5 convertase classical pathway"
After the creation of C5 convertase (either as (C3b)2BbP or C4b2a3b from the classical pathway), the complement system follows ... The alternative pathway is one of three complement pathways that opsonize and kill pathogens. The pathway is triggered when the ... This complex is also known as a fluid-phase C3-convertase. This convertase, the alternative pathway C3-convertase, although ... The C5-convertase of the alternative pathway consists of (C3b)2BbP (sometimes referred to as C3b2Bb). ...
... complement component C5 convertase. Now EC 188.8.131.52, classical-complement-pathway C3/C5 convertase EC 184.108.40.206: complement ... complement subcomponent C1s EC 220.127.116.11: classical-complement-pathway C3/C5 convertase EC 18.104.22.168: Transferred entry: ... factor I EC 22.214.171.124: complement factor D EC 126.96.36.199: alternative-complement-pathway C3/C5 convertase EC 188.8.131.52: ... Proprotein convertase 1 EC 184.108.40.206: Proprotein convertase 2 EC 220.127.116.11: Snake venom factor V activator EC 18.104.22.168: ...
The classical pathway C5 convertase is composed of the larger fragments of complement proteins, C4b, C2b produced by cleavage ... The complement component C5 can be also activated by fluid phase C5 convertase. C5 is activated by CVFBb in the presence of ... Target of function The target of C5 convertase is complement protein C5. C5 is a two-chain (α, β) plasma glycoprotein (Mr = ... or the alternative pathway (C3bBbC3b) of complement system. Two fluid phase C5 convertases have been described: the classical ...
... two regulators of complement. The membrane attack complex is initiated when the complement protein C5 convertase cleaves C5 ... All three pathways of the complement system (classical, lectin and alternative pathways) initiate the formation of MAC. Another ... Terminal complement pathway deficiency Peitsch MC, Tschopp J (1991). "Assembly of macromolecular pores by immune defense ... Deficiencies of C5 to C9 components does not lead to generic infections, but only to increased susceptibility to Neisseria spp ...
C3b binds to the C3 convertase (C4bC2a), to form C5 convertase (C4bC2aC3b). C5 convertase then cleaves C5 into C5a and C5b. ... Alternative complement pathway - another complement system pathway Lectin pathway - another complement system pathway Noris, ... The classical complement pathway is one of three pathways which activate the complement system, which is part of the immune ... Activation of the complement pathway through the classical, lectin or alternative complement pathway is followed by a cascade ...
"Formation of classical C3 convertase during the alternative pathway of human complement activation". PubMed Article. Retrieved ... It is a membrane protein and regulates also C5 convertase of the classical and alternative pathway. DAF protects host cells ... C3 convertase can be used to refer to the form produced in the alternative pathway (C3bBb) or the classical and lectin pathways ... C3 convertase formation can occur in three different pathways: the classical, lectin, and alternative pathways. Cleavage of ...
In the classical and lectin pathways of complement activation, formation of the C3-convertase and C5-convertases requires ... The protein encoded by this gene is part of the classical pathway of the complement system, acting as a multi-domain serine ... C2b is the larger, enzymatically active fragment which is incorporated into the C3 convertase in this pathway, C4b2b. C2a is ... a fragment of complement component C2 produced during C3 convertase formation". Acta Crystallographica D. 65 (Pt 3): 266-74. ...
... iC3b C5 - C5a C3-convertase C5-convertase Late stage Membrane attack complex (MAC) C6 C7 C8 C9 Complement pathway inhibitors C1 ... system Complement system Classical complement pathway Mannan-binding lectin pathway Alternate complement pathway Complement ... divided by pathway) Classical complement pathway C1Q complex - C1R / C1S C4 - C4a C2 Mannan-binding lectin pathway MASP1 / ... Classical, Lectin, Alternate Decay-accelerating factor (CD59) - Classical, Lectin, Alternate Factor I - Classical, Lectin, ...
The complex of C3b(2)Bb is a protease which cleaves C5 into C5b and C5a. C5 convertase is also formed by the Classical Pathway ... Three biochemical pathways activate the complement system: the classical complement pathway, the alternative complement pathway ... Lectin pathwayEdit. Main article: Lectin pathway. The lectin pathway is homologous to the classical pathway, but with the ... The three pathways of activation all generate homologous variants of the protease C3-convertase. The classical complement ...
The complex of C3b(2)Bb is a protease which cleaves C5 into C5b and C5a. C5 convertase is also formed by the Classical Pathway ... Three biochemical pathways activate the complement system: the classical complement pathway, the alternative complement pathway ... The three pathways of activation all generate homologous variants of the protease C3-convertase. The classical complement ... C4b and C2a then bind together to form the classical C3-convertase, as in the classical pathway. Ficolins are homologous to MBL ...
... classical pathway, alternative pathway and lectin pathway) that ultimately lead to the formation of a C3 convertase. Formation ... In such cases treatment with the complement-inhibitory anti-C5 monoclonal antibody, eculizumab, is found to be highly effective ... In the classical pathway, the microbial pathogen is coated in antibodies (IgG and IgM) released by B cells. The C1 complement ... Additionally, C3b plays a role in forming a C3 convertase when bound to Factor B (C3bBb complex), or a C5 convertase when bound ...
... participates in all three of the complement pathways (classical, alternative, and lectin); the alternative pathway is " ... C5 binding sites, 4) private allelic residues. Additionally, the same study identified the expression of human complement C4 ... the C4b-C2a complex with protease activity has been termed the C3 convertase. Protein 4b can be further cleaved into 4c and 4d ... In the classical pathway, the complement component-hereafter abbreviated by the "C" preceding the protein number- termed C1s, a ...
... complement c5 convertase, alternative pathway MeSH D12.776.124.486.274.860.387.750 -- complement c3-c5 convertases, classical ... complement c3 convertase, classical pathway MeSH D12.776.124.486.274.860.387.750.750 -- complement c5 convertase, classical ... complement c3-c5 convertases MeSH D12.776.124.486.274.860.387.500 -- complement c3-c5 convertases, alternative pathway MeSH ... complement c4a MeSH D12.776.124.486.274.350.260 -- complement c4b MeSH D12.776.124.486.274.450 -- complement c5 MeSH D12.776. ...
MASP2 and initiate the lectin pathway of complement activation which is somewhat similar to the classical complement pathway. ... C3 is cleaved into its a and b subunits, and C3b binds the convertase. These together are called the C5 convertase. Similarly ... dependent signaling pathway. MyD88 - dependent pathway is induced by various PAMPs stimulating the TLRs on macrophages and ... dependent pathway and triggers the signaling through NF-κB and the MAP kinase pathway and therefore the secretion of pro- ...
C1s cleaves C4 and C2, which eventually leads to the production of the classical pathway C3-convertase. ... classical pathway. • immune system process. • innate immune response. • complement activation, lectin pathway. • complement ... Complement component 1s (EC 22.214.171.124, C1 esterase, activated complement C1s, complement C overbar 1r, C1s) is a protein ... Sim RB (1981). "The human complement system serine proteases C1r and C1s and their proenzymes". Methods in Enzymology. 80 Pt C ...
The lectin pathway is a type of cascade reaction in the complement system, similar in structure to the classical complement ... C3 convertase is, in classical terms, C4b2a.. Clinical significance. It has been found that people deficient in MBL experience ... In contrast to the classical complement pathway, the lectin pathway does not recognize an antibody bound to its target. The ... The MASPs are very similar to C1r and C1s molecules of the classical complement pathway, respectively, and are thought to have ...
fr C3 convertase classique * en classical-complement-pathway C3/C5-convertase Immunologia ... C3/C5-convertasa de la via clàssica del complement C3/C5-convertasa de la via clàssica del complement ... ca C3/C5-convertasa de la via clàssica del complement, n f ... es C3/C5-convertasa de la vía clásica del complemento * ... Enzim que actua en la confluència de la via clàssica del complement amb la via alternativa i amb la via de la lectina i que ...
C5 convertases of the alternative and classical pathways of complement are complex serine proteases that are made up of two or ... Covalent association of C3.b with C4b within C5 convertase of the classical complement pathway. J. Exp. Med. 165: 1494. ... Distal recognition site for classical pathway convertase located in the C345C/Netrin module of complement C5. J. Immunol. 165: ... Localization of the covalent C3b-binding site on C4b within the complement classical pathway C5 convertase, C4b2a3b. J. Biol. ...
Mouse complement C4 has an inherently low classical pathway C5 convertase subunit activity in vitro and in vivo (3, 17, 61), ... Mouse complement component C4 is devoid of classical pathway C5 convertase subunit activity. Mol. Immunol. 33:297-309. ... 5) (52). In C1q-deficient mice, which cannot activate complement by the antibody-dependent classical pathway, 14NS1, 16NS1, and ... and 17NS1 retained protective activity without triggering the classical pathway of complement activation. It should be noted ...
Alternative pathway (AP) C5 convertases were generated on small streptavidin beads that were coated with purified C3b molecules ... The C5 convertase is a multi-molecular protease complex that catalyses the cleavage of native C5 into its biologically ... Finally, we define two interfaces on C5 important for its recognition by surface-bound C5 convertases. We establish a highly ... Through development of a highly purified model system for C5 convertases, we here aim to provide insights into the surface- ...
Covalent association of C3b with C4b within C5 convertase of the classical complement pathway. Takata, Y., Kinoshita, T., ... CD59, an LY-6-like protein expressed in human lymphoid cells, regulates the action of the complement membrane attack complex on ... Complement-mediated tumor cell damage induced by antibodies against membrane cofactor protein (MCP, CD46). Seya, T., Hara, T., ... Membrane cofactor protein (MCP or CD46): newest member of the regulators of complement activation gene cluster. Liszewski, M.K ...
After the creation of C5 convertase (either as (C3b)2BbP or C4b2a3b from the classical pathway), the complement system follows ... The alternative pathway is one of three complement pathways that opsonize and kill pathogens. The pathway is triggered when the ... This complex is also known as a fluid-phase C3-convertase. This convertase, the alternative pathway C3-convertase, although ... The C5-convertase of the alternative pathway consists of (C3b)2BbP (sometimes referred to as C3b2Bb). ...
In this chapter, we focus on the clinical consequence of dysregulation of the alternative pathway (AP) of complement. We first ... The complement system is the cornerstone of innate immunity. As one of the first lines of host defense, it plays a major role ... Covalent binding of C3b to C4b within the classical complement pathway C5 convertase. Determination of amino acid residues ... By binding to C5, it prevents C5 convertase-mediated cleavage of C5 to C5a and C5b. Because C5b is not formed, the MAC cannot ...
... two regulators of complement. The membrane attack complex is initiated when the complement protein C5 convertase cleaves C5 ... All three pathways of the complement system (classical, lectin and alternative pathways) initiate the formation of MAC. Another ... Terminal complement pathway deficiency Peitsch MC, Tschopp J (1991). "Assembly of macromolecular pores by immune defense ... Deficiencies of C5 to C9 components does not lead to generic infections, but only to increased susceptibility to Neisseria spp ...
These include the different forms of C3/C5 convertases in the classical and the alternative pathways of COMPLEMENT ACTIVATION. ... Serine proteases that cleave COMPLEMENT C3 into COMPLEMENT C3A and COMPLEMENT C3B, or cleave COMPLEMENT C5 into COMPLEMENT C5A ... C3 Convertases, Complement; C3-C5 Convertases, Complement; C5 Convertases, Complement; Complement C3 C5 Convertases; Convertase ... Convertase, C3-C5; Convertase, Complement 3; Convertases, Complement C3; Convertases, Complement C3-C5; Convertases, Complement ...
Indeed, it now seems clear that complement first evolved as part of the innate immune system, where it still plays an important ... Although first discovered as an effector arm of the antibody response, complement can also be activated early in infection in ... This activity was said to complement the antibacterial activity of antibody, hence the name. ... Complement was discovered many years ago as a heat-labile component of normal plasma that augments the opsonization of bacteria ...
C2a, a serine protease, then combines with complement factor C4b to generate the C3 or C5 convertase. ... Component C2 which is part of the classical pathway of the complement system is cleaved by activated factor C1 into two ... Component C2 which is part of the classical pathway of the complement system is cleaved by activated factor C1 into two ... Enzyme and pathway databases. Reactomei. R-MMU-166663 Initial triggering of complement. R-MMU-174577 Activation of C3 and C5. R ...
CRP is able to activate the classical pathway of complement,13 serving as a potential link between complement activation and ... 11 DAF prevents the formation and accelerates the decay of the C3 and C5 convertases that act early within the complement ... The classical pathway of complement may be activated by CRP bound to enzymatically degraded low-density lipoprotein.13 The ... Effects of transfected complement regulatory proteins MCP, DAF, MCP/DAF hybrid on complement-mediated swine endothelial cell ...
Abcams Complement C4 ELISA Kit (ab108825) suitable for Cell culture supernatant, Saliva, Milk, Urine, Cerebral Spinal Fluid in ... Non-enzymatic component of C3 and C5 convertases and thus essential for the propagation of the classical complement pathway. ... A Complement C4 specific antibody has been precoated onto 96-well plates and blocked. Standards or test samples are added to ... Complement component C4 is expressed at highest levels in the liver, at moderate levels in the adrenal cortex, adrenal medulla ...
In the classical pathway C5 convertase is composed of C4b2a3b and in the alternative pathway is C3bBbC3b. Both C5 convertases ... Distal Recognition Site for Classical Pathway Convertase Located in the C345C/Netrin Module of Complement Component C5. The ... C5 convertase cleaves C5 about 800 amino acids away from C345C. Other complement proteins such as C6 and C7 interact with C5 at ... This diagram of C5 convertase shows where C5 is cleaved (dotted arrows) to become activated and where the functional C5-C345C ...
The complement system is a network of more than 50 plasma proteins and receptors, which have the role of mediating innate and ... Activation of complement component C5: comparison of C5 convertases of the lectin pathway and the classical pathway of ... Complement activation pathways. The components of complement system can be organised into three major pathways: The classical ... targeted C3/C5 convertase inhibitor for treatment of human complement alternative pathway‐mediated diseases. Blood 118(17): ...
The effect was shown to be specific for the classical and lectin pathways (Fig. 1.4). C1q was found to be the complement ... Therefore, in CP/LP, C3 convertase (C4b2a) was not affected by Efb but C5 convertase (C4b2aC3b) was inhibited, as evidenced by ... A: Classical pathway. B: Lectin pathway. C: Alternative pathway. Fig.ure adapted from Taylor, A. 2008 (Ref. ). ... SSL9, 10, 12-14 were all reported to inhibit both the classical and lectin complement pathways. SSL9 was proposed to directly ...
C3 and C5 convertases of the 3 complement pathways, namely the classical, alternative, and lectin.5 Specifically, CR1 binds to ... to block all complement activation pathways or 10 mM EGTA in the presence of 2 mM MgCl2 (lane 3) to block the classical pathway ... We specifically activated the classical complement pathway using RBCs sensitized with complement-fixing blood group antibodies ... Activation of complement cascade via the antibody-mediated classical pathway can initiate red blood cell (RBC) destruction, ...
CLASSICAL PATHWAY C3 CONVERTASE) and subsequent C4b2a3b (CLASSICAL PATHWAY C5 CONVERTASE). ... complement c3d*complement factor i*complement c1q*complement c4*complement membrane attack complex*classical complement pathway ... complement c3c*mannose binding lectin complement pathway*alternative complement pathway*histocompatibility*complement factor b* ... Taken together, M. catarrhalis interferes with the classical complement activation pathway by binding C4BP to UspA1 and UspA2 ...
... complement C2 and complement factor B, which, respectively, have analogous roles in the classical and alternative pathways of ... Briefly, they are activated by cleavage and function as the serine protease components of the C3/C5 convertases, which play ... Complement B/C2 (IPR011360). Short name: Compl_C2_B Overlapping homologous superfamilies *von Willebrand factor A-like domain ... New structural motifs on the chymotrypsin fold and their potential roles in complement factor B.. EMBO J. 19 164-73 2000 ...
Pathway:Human:Complement Activation Classical]] moved to [[Pathway:Homo sapiens:Complement Activation Classical]]: Renaming ... C5. MASP2. C1QG. C2A. H2O. C3. C8A. C1QA. C4B. C1R. C1S. C1QB. C7. C2. C4B. C3B. C3 convertase. C2A. C4B. C5 convertase. C5B. ... Pathway:Homo sapiens:Complement Activation Classical]] moved to [[Pathway:WP545]]: Moved to stable identifier. 15395. view. 22: ... Ontology Term : classical complement pathway added !. 63169. view. 20:26, 8 May 2013. MaintBot. Updating gpml version. 41148 ...
... complement component 2) for ICC/IF, WB. Anti-Complement C2 pAb (GTX105404) is tested in Human samples. 100% Ab-Assurance. ... CO2 antibody, DKFZp779M0311 antibody, C2 antibody, complement C2 antibody, complement component C2 antibody, C3/C5 convertase ... complement component 2. Background. Component C2 is a serum glycoprotein that functions as part of the classical pathway of the ... The serine proteinase C2a then combines with complement factor 4b to create the C3 or C5 convertase. Deficiency of C2 has been ...
... specific for the C5 component of the activated complement and characterised by the ability to inhibit the conversion of the C5 ... in particular for the therapy of diseases involving tissue damage deriving from uncontrolled activation of the complement ... "Distal recognition site for classical pathway convertase located in the C345C/netrin module of complement component C5," J. ... the antibodies block conversion of C5 by the C5 convertase. This enzyme can be activated by the classical pathway initiated by ...
Component C2 which is part of the classical pathway of the complement system is cleaved by activated factor C1 into two ... C2a, a serine protease, then combines with complement factor 4b to generate the C3 or C5 convertase. ... Defects in C2 are the cause of complement component 2 deficiency (C2D) [MIM:217000]. A deficiency of the complement classical ... Human complement component C2: production and characterization of polyclonal and monoclonal antibodies against C2.. Mol Immunol ...
Preferential inactivation of the C5 convertase of the alternative complement pathway by factor I and membrane cofactor protein ... This pathogen salvages the catalytic complement fragment C2a of the classical pathway C3 convertase and uses it to then deposit ... Regulation of the B cell response to T-dependent antigens by classical pathway complement. J. Immunol. 1996. 157:549-556. View ... The complement deposition is triggered by CRP activation of the classical pathway, followed by amplification of C3 deposition ...
ComplexesPhagocytosisImmuneC4b2aHuman complementC3bBbC4b2a3bDysregulationComponents of the complementInflammatoryEnzymeSerumInitiatesProteolytic cleavageProteasesMoleculeMannose‐bindProperdinEnzymesActivateDepositionBindInhibitionSurface-bound C5 convertasesConvergeSerine proteaseGeneration of C5 convertaseCleaves C5 to generateOpsonizationForm C3 convertaseAlternative pathway activationTriggersPhagocytesFragmentsFragmentCleavage of C3Adaptive immunityTerminal complementInitiateInhibitsComponent of complement
- The results suggest that in serum convertases formed with monomeric C3b will be relatively inefficient in capturing C5 but will continue to cleave C3 opsonizing the cell surface for phagocytosis, whereas convertases formed with C3b-C3b complexes in areas of high C3b density will primarily cleave C5. (jimmunol.org)
- C3 convertases of the alternative pathway (monomeric C3/C5 convertase assembled with monomeric C3b (C3b,Bb)) and the classical pathway (C4b,C2a) are bimolecular complexes ( 1 , 3 ). (jimmunol.org)
- Through development of a highly purified model system for C5 convertases, we here aim to provide insights into the surface-specific nature of these important protease complexes. (biomedcentral.com)
- These fluid phase complexes do not bind to cell membranes and are ultimately scavenged by clusterin and vitronectin, two regulators of complement. (wikipedia.org)
- The complement system, an important arm of innate immunity, provides host defense and physiologic clearance of immune complexes and plays an adjuvant role in the immune response. (asmscience.org)
- The classical pathway (CP) is activated by surface‐bound immune complexes, resulting in cleavage of C4 and thereby generation of C4b ( Figure 1A ). (embopress.org)
- C4b2a is the widely used short‐hand nomenclature for the C4b-C2a complex in the complement field, and similar nomenclature is used for the remaining complexes in the following). (embopress.org)
- Central to innate immunity, complement activation is heightened in pregnancy, 1 in part, to facilitate normal clearance of fetoplacental material, including apoptotic blebs, 2 circulating fetal DNA, 3 and immune complexes. (ahajournals.org)
- In the case of the classical and the lectin pathways, collagen-containing pattern recognition molecules bind to Ag-Ab complexes and carbohydrate residues, respectively, on the surface of the pathogenic cells. (jimmunol.org)
- MBL forms complexes with MBL-associated serine proteases (MASPs), which share a high degree of structural homology with the classical pathway serine proteases C1r and C1s. (frontiersin.org)
- When lectin pathway activation complexes bind to microbial carbohydrates or acetylated ligands, MASP-1 and MASP-2 are converted into their enzymatic active form. (frontiersin.org)
- Both the classical and the lectin pathway share the identical C3 and C5 convertase complexes formed after cleavage of C4 by either activated C1s (classical pathway) or activated MASP-2 (lectin pathway) (see 1) and subsequent cleavage and activation of C4b-bound C2 through activated C1s or MASP-2 (see 2). (asmscience.org)
- The affinity of factor B to bind C3b is higher on "activating "surfaces, and the half-life of C3bB, C3Bb, and C3Bb(C3b)n complexes, significantly increased by the action of properdin, allows the alternative pathway amplification loop to be formed. (asmscience.org)
- Mediates the binding by these cells of particles and immune complexes that have activated complement to eliminate them from the circulation (PubMed:2963069). (nih.gov)
- In contrast, C3, FB, FD, FP and C5, FH and FI attached to ULVWF strings in quantitative patterns consistent with assembly of the AP components into active complexes. (rice.edu)
- This was verified when non-functional FB blocked the formation of AP C3 convertase complexes (C3bBb) on ULVWF strings. (rice.edu)
- Consequently, membrane attack complexes (MAC) are formed on the membrane of target cells (terminal complement), leading to complement-mediated death. (ashpublications.org)
- The various complement activation pathways converge at the formation of active protease complexes called C3 convertases ( 3 ). (asm.org)
- Complement system can be activated by immune complexes and immunologic molecules like endotoxins. (periobasics.com)
- Complement activation is a critical means of host defense against infection and the clearance of immune complexes. (ashpublications.org)
- Complement inflammation is a major inflammatory mechanism whose function is to promote the removal of microorganisms and the processing of immune complexes. (biomedcentral.com)
- Complement activation promotes the removal of microorganisms and the processing of immune complexes. (biomedcentral.com)
- Due to its destructive potential the complement system is heavily regulated but when activated it works largely by forming pore complexes as well as triggering acute inflammation and by promoting phagocytosis by macrophages and neutrophils. (vetbook.org)
- Immune complexes trigger complement activation by binding C1. (vetbook.org)
- 1 , 2 Although IgG1-acetylcholine receptor (AChR) complexes can modulate AChRs by cross-linking and accelerating degradation as well as functionally blocking AChRs, it is the activation of complement through successive stimulation of C3 and C5 convertase that ultimately results in a membrane attack complex with lysis of the post-synaptic muscle endplate. (pubmedcentralcanada.ca)
- One of these is decay-accelerating factor (DAF) or CD55, and its main function is to bind and inactivate pre-formed C3/C5 convertase complexes. (pubmedcentralcanada.ca)
- Moreover, the complement system bridges the innate and adaptive immunity, because the activated complement components facilitate the phagocytosis of pathogens by the host's leukocytes and initiate inflammatory reactions by recruiting and stimulating the cellular elements of the immune system. (jimmunol.org)
- Having been traditionally utilized as a marker of infection and cardiovascular events, there is now growing evidence that CRP plays important roles in inflammatory processes and host responses to infection including the complement pathway, apoptosis, phagocytosis, nitric oxide (NO) release, and the production of cytokines, particularly interleukin-6 and tumor necrosis factor-α. (frontiersin.org)
- The nCRP isoform activates the classical complement pathway, induces phagocytosis, and promotes apoptosis. (frontiersin.org)
- The complement system is a central component of the innate immune response and is involved in many functions, including recognition, opsonization, phagocytosis, and destruction of foreign cells, as well as generation of chemotactic fragments (C3a and C5a) and activation of adaptive immunity ( 30 , 32 , 51 ) Three pathways of complement activation are known: the classical, lectin, and alternative pathways. (pubmedcentralcanada.ca)
- 13 These polysaccharidic components are widely used for bacterial classification, responsible for non-immunological and immunological interactions of bacteria with hosts and also involved in the avoidance of host innate immune mechanisms-such as resistance to phagocytosis, complement-mediated killing, and the bactericidal activity of antimicrobial peptides. (iranjournals.ir)
- Complement activation , Phagocytosis and Inflammatory response. (sqadia.com)
- Complement activation leads to opsonization and enhanced phagocytosis of bacteria. (sqadia.com)
- The effector mechanisms used by antibodies to combat these infections include neutralization, opsonization and phagocytosis, and activation of complement by the classical pathway. (sqadia.com)
- Activation of complement via the innate and the adaptive immune systems is vital to the body's defenses in fighting infections. (jimmunol.org)
- The alternative pathway of the complement system is an innate component of the immune system 's natural defense against infections. (wikipedia.org)
- Indeed, it now seems clear that complement first evolved as part of the innate immune system , where it still plays an important role. (nih.gov)
- Collectively, our data highlight a potential use of CR1-based inhibitors for prevention of complement-dependent immune hemolysis. (bloodjournal.org)
- The complement system is an important mediator of the host immune response to infection and tissue damage, but may cause substantial injury when activated inappropriately. (bloodjournal.org)
- In immune destruction of red blood cells (RBCs), complement plays a critical role, being involved in both intravascular and extravascular hemolysis. (bloodjournal.org)
- Indeed, as many as 50% of patients with immune hemolytic diseases have both IgG and complement on their red cells. (bloodjournal.org)
- 4 Because of the contribution of complement in RBC destruction, we have taken the approach of activation using recombinant complement inhibitory molecules to block complement-mediated immune hemolysis, and thereby prevent some of its associated life-threatening effects. (bloodjournal.org)
- We propose that this localized deposition of complement fragments aids in the fusion process between the spermatozoa and egg, in a role akin to that of complement in immune adherence. (jci.org)
- The complement system, an essential part of the innate immune system, can be activated through three distinct routes: the classical, the alternative, and the lectin pathways. (jimmunol.org)
- Thus, the complement system provides the first line of defense before the adaptive immune response builds up. (jimmunol.org)
- The proteolytic processing of C3 generates an array of cleavage products that are involved in the amplification of complement activity through the formation of C3 and C5 convertases, the opsonization of pathogens, and the attraction and activation of leukocytes of both the innate and adaptive arms of the immune response. (asm.org)
- The complement system provides a fundamental component of the body's immune response to invading microorganisms. (asmscience.org)
- This chapter highlights the various roles of the complement system in the orchestration of the immune response towards microbial infections, gives examples of microbial strategies to evade complement-mediated clearance, and discusses how acquired and inherited complement deficiencies may predispose an organism to infectious disease. (asmscience.org)
- Among its related pathways are Immune response Lectin induced complement pathway and Complement Pathway . (genecards.org)
- The complement system is a key component of the innate immune system, activation of which results in production of C3b (from C3), which is a key opsonic factor reactive with receptors on phagocytes to promote internalization of bacteria and their subsequent destruction. (hindawi.com)
- The term "complement" was introduced by Paul Ehrlich in the late 1890s, as part of his larger theory of the immune system. (wikidoc.org)
- Ehrlich therefore named this heat-labile component "complement", because it is something in the blood which "complements" the cells of the immune system. (wikidoc.org)
- The classical complement pathway typically requires antibodies for activation (specific immune response), while the alternative and mannose-binding lectin pathways can be activated by C3 hydrolysis or antigens without the presence of antibodies (non-specific immune response). (wikidoc.org)
- During this journey, from circulating cells to endothelial cells, C. pneumoniae encounters the innate immune system, in which the complement system may play a fundamental role in controlling Chlamydia infection. (pubmedcentralcanada.ca)
- Complement, a key part of the innate immune system, is composed of multiple components and needs to be activated to function. (ashpublications.org)
- Evaluation of Pasteurella multocida serotype B:2 resistance to immune serum and complement system', Veterinary Research Forum , 8(3), pp. 179-184. (iranjournals.ir)
- In the present study, the possible bactericidal activity of immune calf sera in the presence and absence of complement system was investigated. (iranjournals.ir)
- Results were indicative of the presence of inhibitory mechanism(s) in P. multocida B:2 against bactericidal activity of immune calf serum and complement system. (iranjournals.ir)
- The complement mediators are the major effectors of the immune balance, which operates at the interface between the innate and adaptive immunity, and is vital for many immunoregulatory functions. (biomedcentral.com)
- The mannose-binding lectin pathway can be activated by C3 hydrolysis or antigens without the presence of antibodies non-specific immune response. (rhein-main-verzeichnis.info)
- In renal transplant, the allograft is responsible for triggering many innate and adaptive immune mechanisms, either mediated by cells, such as macrophages and lymphocytes, or by soluble components, such as antibodies and the complement system, which can ultimately lead to graft rejection [ 1 ]. (hindawi.com)
- The complement system can be recruited and brought into action by antibodies generated by the adaptive immune system . (wikipedia.org)
- Ehrlich introduced the term "complement" as part of his larger theory of the immune system. (wikipedia.org)
- The complement system is a part of the larger immune system and three biochemical pathways are present: the classical complement pathway, the alternative pathway, and the mannose-binding lectin pathway. (adipogen.com)
- Complement component C4 is an essential component of humoral immune response. (adipogen.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)
- In addition to being a component of innate immunity and an ancient defense mechanism against invading pathogens, complement activation also participates in the adaptive immune response, inflammation, hemostasis, embryogenesis, and organ repair and development. (jci.org)
- Here we report that MASP-2 deficient mice (which can still activate complement via the classical pathway and the alternative pathway) are highly susceptible to pneumococcal infection and fail to opsonize Streptococcus pneumoniae in the none-immune host. (dmu.ac.uk)
- This gene encodes a component of the complement system, a part of the innate immune system that plays an important role in inflammation, host homeostasis, and host defense against pathogens. (nih.gov)
- Proteolysis of C4 is also triggered via recognition of microbial carbohydrates in the lectin pathway (LP). C4b combines with C2 and subsequent cleavage of C2 to C2a results in generation of the LP/CP C3 convertase C4b2a. (embopress.org)
- The end result is cleavage of C4 and C2 to form C4b2a, the C3 convertase that will then generate C3a and C3b. (hindawi.com)
- C4b and C2a form together C4b2a, which is known as the C3 convertase . (lecturio.com)
- The C-terminal fragment C2a consisting of a serine protease (SP) and a von Willebrand factor type A (vWFA) domain, remains attached to C4b, forming the C3-convertase, C4b2a. (uab.edu)
- The C4b2a complex is also known as C3 convertase as this converts C3 into an active form by separating C3a and C3b. (microbeonline.com)
- The remaining α chain fragment C4b is the major activation product and is an essential subunit of the C3 convertase (C4b2a) and the C5 convertase (C3bC4b2a) enzymes of the classical complement pathway. (adipogen.com)
- Human complement component C2: production and characterization of polyclonal and monoclonal antibodies against C2. (abcam.com)
- The structures of the von Willebrand factor A and serine protease domains from human complement factor B ( P00751 ) have been analysed [ PMID: 15016353 , PMID: 10637221 ]. (ebi.ac.uk)
- 1. Kerr, M.A. The second component of human complement. (qmul.ac.uk)
- The crystal structure of C2a, the catalytic fragment of classical pathway C3 and C5 convertase of human complement. (uab.edu)
- The human complement system is an important component of innate immunity. (uab.edu)
- A single arginine to tryptophan interchange at beta-chain residue 458 of human complement component C4 accounts for the defect in classical pathway C5 convertase activity of allotype C4A6. (moldiag.com)
- The complete exon-intron structure of a human complement component C4A gene. (moldiag.com)
- Null alleles of human complement C4. (moldiag.com)
- Polymorphism of the human complement C4 and steroid 21-hydroxylase genes. (moldiag.com)
- Step 2 is the formation of C3 convertase, C3bBb. (asmscience.org)
- The alternative pathway (AP) C3 convertase C3bBb is formed when factor B (fB) combines with C3b, after which fB is activated by factor D (fD) ( Figure 1A ). (embopress.org)
- C3bBb acts as C3 convertase which cleaves C3 - this creates a continuous loop and many C3b can be deposited on the invader's cell surface. (epomedicine.com)
- Decay Accelerating Factor (DAF) accelerates destruction of C3 convertase (C3bBb). (epomedicine.com)
- Here, we present the crystal structure of Mg(2+)-bound C2a to 1.9 A resolution in comparison to its homolog Bb, the catalytic subunit of the alternative pathway C3-convertase, C3bBb. (uab.edu)
- After the creation of C5 convertase (either as (C3b) 2 BbP or C4b2a3b from the classical pathway), the complement system follows the same path regardless of the means of activation (alternative, classical, or lectin). (wikipedia.org)
- In the classical pathway C5 convertase is composed of C4b2a3b and in the alternative pathway is C3bBbC3b. (davidson.edu)
- Pangburn and Rawal, 2002 ) to form a C5 convertase (C3bBb3b or C4b2a3b), which cleaves C5 to generate the large fragment C5b and the anaphylatoxin C5a ( Figure 1A ). (embopress.org)
- C5a is a 77 amino acid peptide that is created by the C5a convertase proteolytic cleavage of C5 αchain in the classical and alternative complement pathway (C4b2a3b, C3bBb3b). (sinobio.net)
- C4b2a4b in the classical pathway, C4b2a3b in the lectin pathway, and C3b2Bb in the alternative pathway. (wordpress.com)
- Dysregulation of the complement system has been implicated in several diseases and pathologies. (wikipedia.org)
- In this chapter, we focus on the clinical consequence of dysregulation of the alternative pathway (AP) of complement. (asmscience.org)
- Dysregulation of complement activity has, therefore, been connected to various diseases, including autoimmune conditions, thrombotic pathologies and infections. (els.net)
- Complement dysregulation and deficiencies are connected to disease. (els.net)
- Consequently, biomarkers of complement dysregulation may be useful for prediction or treatment of disease. (ahajournals.org)
- Because renal damage with proteinuria is a characteristic pathological feature of preeclampsia, we hypothesized that complement markers in urine, rather than plasma, could better reflect complement dysregulation in disease. (ahajournals.org)
- however, they did not distinguish preeclampsia from chronic hypertension, supporting our hypothesis that complement markers in urine, rather than plasma, better reflect complement dysregulation. (ahajournals.org)
- Dense deposit disease (DDD) and C3 glomerulonephritis (C3GN) are two ultra-rare renal diseases characterized by fluid-phase dysregulation of C3 and C5 convertases that can lead to partial or complete consumption of circulating complement components, including C3. (uiowa.edu)
- These histological features are referred to as C3 glomerulonephritis and imply that dysregulation of the complement alternative pathway ( Fig. 1 ) is central to the pathophysiology of the disease. (biologists.org)
- In C3 glomerulopathy, a high percentage of patients have circulating levels of the autoantibody called C3NeF, which causes systemic dysregulation of the complement system. (revistanefrologia.com)
- C5a, the smaller fragment, is a potent chemotactic and spasmogenic anaphylatoxin that mediates inflammatory responses by stimulating platelets, endothelial cells, eosinophils, neutrophils, and phagocytes to the site of complement activation ( 4 , 5 ). (jimmunol.org)
- The anaphylatoxins C3a and C5a mediate the inflammatory responses of complement. (els.net)
- Derived from proteolytic degradation of complement C4, C4a anaphylatoxin is a mediator of local inflammatory process. (abcam.com)
- 6 The burden of fetoplacental debris becomes exaggerated in severe preeclampsia, 7 - 10 propagating a systemic inflammatory response and placing strain on both classical and alternative complement signaling pathways ( Figure 1 ) as early as the first trimester. (ahajournals.org)
- The significance of complement activation, a major inflammatory mechanism, in AD is particularly problematic. (biomedcentral.com)
- Complements are activated only during inflammatory reactions. (microbeonline.com)
- Further, it highlights activation of inflammatory cells (Basophils, PMNs and Macrophages) through complement receptor binding and downstream release of inflammatory mediators. (biomedcentral.com)
- These findings have relevance to the cellular events of complement activation underling the pathogenesis of AMD, and highlight the potential of 670-nm light as a non-invasive anti-inflammatory therapy. (biomedcentral.com)
- There is increasing evidence for functional crosstalk between inflammatory and thrombotic pathways in inflammatory vascular diseases such as atherosclerosis and vasculitis. (bloodjournal.org)
- Complement by-products stimulate inflammatory response by recruiting and activating leukocytes Phagocytes use surface receptors (mannose receptors, scavenger receptors), to recognize extracellular bacteria. (sqadia.com)
- Components C3 and C5 are involved in the generation of anaphylatoxin and in the promotion of leukocyte chemotaxis, the result of these two activities being the inflammatory response. (thefreedictionary.com)
- The catalytic rate of these convertases approaches maximum velocity, thereby switching the enzyme from cleavage of C3 to cleavage of C5, and production of the cytolytic C5b-9 complex. (jimmunol.org)
- The study of C5 convertases has been difficult because the enzyme complex that cleaves C5 is the same serine protease (C3 convertase) that cleaves C3 ( 1 ). (jimmunol.org)
- Cleavage of C3 produces the proteolytically activated form of C3 (C3b), 3 which forms the nonenzymatic subunit of the enzyme complex responsible for C3 and C5 cleavage ( 1 , 3 ). (jimmunol.org)
- The alternative pathway C3 convertase (C3b,Bb) has C3b as the noncatalytic subunit attached in a Mg 2+ -dependent fashion to the catalytic subunit (Bb) of the enzyme complex. (jimmunol.org)
- The natural surface-bound C5 convertases are the more complex forms of the enzyme and are made up of a C3 convertase and an additional C3b molecule ( 6 , 7 , 8 , 9 , 10 , 11 , 13 , 14 ). (jimmunol.org)
- Both pathways lead to the formation of a common C3 convertase, an enzyme complex with serine proteinase trypsin‐like specificity. (els.net)
- Abcam's Complement C4 Human in vitro ELISA (Enzyme-Linked Immunosorbent Assay) kit is designed for the quantitative measurement of Complement C4 levels in urine, milk, saliva, CSF and cell culture supernatants. (abcam.com)
- C5 complement system plays a chemotactic agent by attracting the neutrophils and this neutrophil can produce the enzyme that could damage the endothelial cells of the blood vessels resulting release of the red blood cell from the blood vessels. (gazetteactuartistes.com)
- We have recently established a mouse strain deficient of the lectin pathway effector enzyme mannan-binding lectin associated serine protease-2 (MASP-2) and shown that this mouse strain is unable to form the lectin pathway specific C3 and C5 convertases. (dmu.ac.uk)
- however, in two patients with nephritic factor in their serum fractional catabolism of C5 was normal despite markedly increased C3 turnover, suggesting that in patients with alternative pathway activation by nephritic factor little or no C5 convertase is generated. (curehunter.com)
- Component C2 is a serum glycoprotein that functions as part of the classical pathway of the complement system. (genetex.com)
- The results showed that P. multocida B:2 is highly resistant to positive serum, containing high levels of IgG and IgM obtained from calves after vaccination, and complement activity in normal fresh calf serum. (iranjournals.ir)
- The destructive effects of fresh serum on gram-negative bacteria is assumed to be one of the consequences of the activity of host complement system. (iranjournals.ir)
- More than 20 types of complements are present in serum, found circulating normally in human body in inactive forms (called as zymogens or proenzymes) . (microbeonline.com)
- In the first, also referred to as the test system, antigen is mixed usually with serial dilutions of a test serum in the presence of complement. (thefreedictionary.com)
- Our previous studies found that antimannan immunoglobulin G (IgG) in normal human serum (NHS) allows C. albicans to initiate the classical pathway. (asm.org)
- A naturally occurring antimannan immunoglobulin G (IgG) is required for activation of the classical pathway by C. albicans yeast cells incubated in normal human serum (NHS) ( 21 , 40 ). (asm.org)
- Our interest has focused on the observed difference in the time required for C3 accumulation via the alternative pathway on C. albicans yeast cells incubated in EGTA-chelated serum versus mannan-absorbed serum. (asm.org)
- C5 convertases of the alternative and classical pathways of complement are complex serine proteases that are made up of two or more subunits ( 1 , 6 , 7 , 8 , 9 , 10 , 11 ). (jimmunol.org)
- In this paper, we report lectin pathway-specific short peptide inhibitors developed by phage display against mannose-binding lectin-associated serine proteases (MASPs), MASP-1 and MASP-2. (jimmunol.org)
- Both peptides block the lectin pathway activation completely while leaving the classical and the alternative routes intact and fully functional, demonstrating that of all complement proteases only MASP-1 and/or MASP-2 are inhibited by these peptides. (jimmunol.org)
- This leads to activation, depending on the species, of mannan-binding lectin-associated serine proteases [ 1 - 3 ] (MASP), the first two proteases being similar to C1r and C1s of the classical pathway. (hindawi.com)
- the activation of proteases (caspases) commits the cell to mitochondrial or death receptor pathways. (brainscape.com)
- In the classical pathway C3 convertase C4b,C2a has a structure similar to the alternative pathway C3 convertase in having C2a as the catalytic subunit noncovalently bound to a C4b molecule. (jimmunol.org)
- High C5 convertase activity was associated with the formation of C3b-C3b or C3b-C4b dimers in which the additional C3b molecule was shown to be covalently attached to a specific site on the first C3b or C4b molecule ( 10 , 16 ). (jimmunol.org)
- The C5 molecule has a molecular weight of about 190 kDa and consists of two polypeptide chains (α, 115 kDa and β, 75 kDa) which are connected by disulfide bonds. (davidson.edu)
- 21. The C3b binding molecule of claim 1, wherein the C3b binding molecule inhibits C3b binding to a convertase. (patentsencyclopedia.com)
- The addition of properdin forms the complex C3bBbP, a stable compound which can bind an additional C3b to form alternative pathway C5-convertase. (wikipedia.org)
- This nonproteolytically activated form of C3 can lead to the formation of the alternative pathway C3 convertase by interacting with factors B and D. This convertase formation can be further induced and stabilised by properdin. (els.net)
- The activation of the alternative pathway is initiated by slow and spontaneous deposition of C3 onto foreign surfaces, although recently it has been shown that properdin can act as a recognition component in this pathway ( 4 ). (jimmunol.org)
- Factor B, factor D, and properdin (factor P) are specific components of the alternative pathway of complement activation. (asmscience.org)
- C3b generates new C3 convertases by interacting with factors B, D and properdin. (uiowa.edu)
- Recently, properdin, a positive regulator of the alternative pathway of complement, has been shown to bind to surfaces and promote complement activation. (pubmedcentralcanada.ca)
- Here we studied whether properdin-mediated complement activation occurs on the surface of Chlamydia pneumoniae , an obligate intracellular Gram-negative bacterium that causes 10 to 20% of community-acquired pneumonia. (pubmedcentralcanada.ca)
- All initiation pathways converge in the formation of short-lived C3 convertase enzymes on the target surface. (biomedcentral.com)
- Potential roles in the proteolytic activation of C3 and C5 have also been assigned to noncomplement proteinases, including enzymes of the coagulation and fibrinolysis cascades. (els.net)
- Yet C3b can activate C5 to induce the lytic sequence . (lecturio.com)
- Only IgM and IgG can activate complement. (periobasics.com)
- The activated C1will activate C4 and C2 resulting C3 convertase. (gazetteactuartistes.com)
- Opsonophagocytosis is initiated when bacterial surfaces activate complement through the alternative pathway (reviewed in ). (prolekare.cz)
- Only IgM and certain IgG subclasses can activate complement this way. (vetbook.org)
- Treatment with sCR1 increased the survival of transfused human group A RBCs in the circulation of mice with pre-existing anti-A for 2 hours after transfusion by 50%, reduced intravascular hemolysis, and lowered the levels of complement deposition (C3 and C4), but not immunoglobulin G (IgG) or IgM, on the transfused cells by 100-fold. (bloodjournal.org)
- The binding of these physiological forms accelerates complement activation on the Chlamydia pneumoniae surface, as measured by C3b and C9 deposition. (pubmedcentralcanada.ca)
- The increased DAF expression was functionally relevant because it significantly reduced C3 deposition and complement-mediated EC lysis. (bloodjournal.org)
- In turn, surface bound C3 convertase promotes accelerated cleavage of C3 into C3a and C3b, thereby promoting opsonization by amplifying C3b deposition through ester bond formation with hydroxyl groups present on the bacterial surface. (prolekare.cz)
- complement deposition has been observed at the muscle endplate of human subjects with MG and in experimental allergic MG (EAMG). (pubmedcentralcanada.ca)
- C3 deposition via the antimannan IgG-dependent classical pathway occurs rapidly and can be detected within 1 min following incubation of the yeast cells with NHS ( 40 ). (asm.org)
- C3 deposition through the alternative pathway exhibits distinctly different characteristics. (asm.org)
- Alternatively, the naturally occurring antimannan IgG that is present in EGTA-chelated NHS may facilitate C3 deposition via the alternative pathway. (asm.org)
- 13 ) revealed that the role of the additional C3b was to bind the substrate, C5. (jimmunol.org)
- The hydrolysis induces a conformational change that allows factor B to bind and form the alternative complement activation pathway C3 convertase (amplification loop is represented by the bold dotted arrow). (els.net)
- Once C3b is formed - it can either follow alternative pathway or bind to C4bC2a (C3 convertase) to form C5 convertase. (epomedicine.com)
- APL-1 and APL-2, are derivatives of Compstatin, bind to and inhibit complement activation at the C3 level, thus blocking all major effector pathways of complement activation. (biomedcentral.com)
- C4b and C2a bind to form C3-convertase. (adipogen.com)
- The structures reveal a parallel two‐point attachment between C5 and CVF, where the presence of SSL7 only slightly affects the C5-CVF interface, explaining the IgA dependence for SSL7‐mediated inhibition of C5 cleavage. (embopress.org)
- Complement inhibition is an intriguing treatment option for patients with severe preeclampsia. (ahajournals.org)
- Acts also in the inhibition of spontaneous complement activation by impairing the formation and function of the alternative and classical pathway C3/C5 convertases, and by serving as a cofactor for the cleavage by factor I of C3b to iC3b, C3c and C3d,g, and of C4b to C4c and C4d (PubMed:2972794, PubMed:8175757). (nih.gov)
- This results in inhibition of the classical and lectin pathway of complement activation, probably due to interference with binding of C2a to C4b such that C3 convertase cannot be formed. (genecards.org)
- 4 This concept has been supported by studies including those using C3 knockout (KO) mice or C3 inhibitors in mice, in which complement-mediated hemolysis (both extravascular and intravascular) was shown to be significantly reduced in various models in the absence or inhibition of mouse C3. (ashpublications.org)
- Inhibition of complement activation on the surface of cells after incorporation of decay-accelerating factor (DAF) into their membranes. (rupress.org)
- Three activation pathways converge at the formation of C3 convertases, cleaving C3 into C3a and C3b. (embopress.org)
- All of the activating pathways converge to form C3 convertases. (ashpublications.org)
- The three complement activation pathways (alternative, classical, lectin) converge at the stage of C3 cleavage to generate the activated form of C3, which is C3b. (uiowa.edu)
- These 3 pathways converge at the component C3. (medscape.com)
- The soluble serine protease C3 convertase (C3b,Bb) assembled with monomeric C3b has been shown to be the simplest form of C5 convertase ( 12 ). (jimmunol.org)
- C2a, a serine protease, then combines with complement factor C4b to generate the C3 or C5 convertase. (uniprot.org)
- CVF functions as a relatively rigid binding scaffold inducing a conformational change in C5, which positions its cleavage site in proximity to the serine protease Bb. (embopress.org)
- The multi-domain serine protease C2 provides the catalytic activity for the C3 and C5-convertases of the classical and lectin pathways of complement activation. (uab.edu)
- FUNCTION: This gene encodes a serine protease that plays an important role in the classical and alternative complement pathways where it cleaves C4b and C3b components of C3 and C5 convertases. (utsouthwestern.edu)
- The third pathway of complement activation is related to the constant, spontaneous hydrolysis of C3, resulting in formation of C3b, which then triggers complement activation. (hindawi.com)
- Cleavage of C3 yields C3a and C3b, the latter of which triggers the formation of the C5 convertase. (ashpublications.org)
- Both fragments play a vital role in killing microorganisms and in eliminating targets of complement action. (jimmunol.org)
- Further degradation of C4b by C1 into the inactive fragments C4c and C4d blocks the generation of C3 convertase. (abcam.com)
- A complex of complement fragments C4b, C2a and C2b. (qmul.ac.uk)
- Complement component 3 (C3) occupies a central position because of the manifold biological activities of its activation fragments, including the major fragment, C3b, which anchors the assembly of convertases effecting C3 and C5 activation. (uab.edu)
- The large fragment formed when COMPLEMENT C4 is cleaved by COMPLEMENT C1S. (labome.org)
- 3. The combination according to claim 1 or 2, wherein the epitope is selected from within a fragment consisting of amino acids 33-124 of the beta chain (SEQ ID NO: 1) or a fragment consisting of amino acids 1-999 of the alpha chain (SEQ ID NO: 10) of C5. (patents.com)
- The structure of C2b, a fragment of complement component C2 produced during C3 convertase formation. (uab.edu)
- Investigations into the role of complement in ischemia/reperfusion (I/R) injury have identified common effector mechanisms that depend on the production of C5a and C5b-9 through the cleavage of C3. (frontiersin.org)
- Less clear however is the mechanism of complement activation that leads to the cleavage of C3 in ischemic tissues and to what extent the potential trigger mechanisms are organ dependent - an important question which informs the development of therapies that are more selective in their ability to limit the injury, yet preserve the other functions of complement where possible. (frontiersin.org)
- Both provide a path to the cleavage of C3 which is a central event in complement activation. (vetsci.co.uk)
- Production of C3-convertase leads to cleavage of C3 into C3a and C3b and C3b joins with the C3 convertase to make C5 convertase. (adipogen.com)
- However, a fluid‐phase AP C3 convertase C3(H 2 O)Bb can also assemble after spontaneous hydrolysis of the C3 thioester and initiate the AP ( Pangburn and Muller‐Eberhard, 1983 ). (embopress.org)
- A single pentameric IgM can initiate the pathway, while several, ideally six, IgGs are needed. (rhein-main-verzeichnis.info)