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.
The destruction of ERYTHROCYTES by many different causal agents such as antibodies, bacteria, chemicals, temperature, and changes in tonicity.
A condition of inadequate circulating red blood cells (ANEMIA) or insufficient HEMOGLOBIN due to premature destruction of red blood cells (ERYTHROCYTES).
Proteins from BACTERIA and FUNGI that are soluble enough to be secreted to target ERYTHROCYTES and insert into the membrane to form beta-barrel pores. Biosynthesis may be regulated by HEMOLYSIN FACTORS.
Substances that are toxic to blood in general, including the clotting mechanism; hematotoxins may refer to the hematopoietic system.
The sequential activation of serum COMPLEMENT PROTEINS to create the COMPLEMENT MEMBRANE ATTACK COMPLEX. Factors initiating complement activation include ANTIGEN-ANTIBODY COMPLEXES, microbial ANTIGENS, or cell surface POLYSACCHARIDES.
A 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.
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).
Acquired hemolytic anemia due to the presence of AUTOANTIBODIES which agglutinate or lyse the patient's own RED BLOOD CELLS.
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.

Sex-limited protein: in vitro and in vivo functions. (1/96)

Mouse complement component C4 exists in two isoforms, C4 and a protein with expression restricted to male animals called sex-limited protein (Slp). Although Slp is about 95% homologous to C4, it is generally believed to be non-functional, at least in conventional haemolytic complement assays. In a previous study, however, we showed that Slp is haemolytically active in a C1-inhibitor (C1INH)-regulated, EDTA-resistant mouse complement activation pathway. To study other possible implications of this finding, we generated constitutively expressing Slp-transgenic mice. The transgene was crossed into otherwise Slp-deficient C57Bl/6J and NZB mice. Members of the third backcross generation of C57Bl/6J mice were tested for functional Slp and classical and alternative complement pathway activities (CH50 and AP50 levels, respectively). Slp-transgenic C57Bl/6J mice showed enhanced CH50, but normal AP50 levels when compared with non-transgenic littermates. To discover a possible protective role for Slp in spontaneous systemic lupus erythematosus (SLE) in NZBxNZW (NZBxW) mice, the third backcross generation of Slp-transgenic NZB mice was mated with NZW mice and the development of SLE in the female offspring was followed. In these introductory experiments, Slp-transgenic NZBxW animals presented with a significantly extended life span. Our results imply that Slp is a mouse complement component with functions which partially resemble some of those of human C4A.  (+info)

Elevated serum levels of soluble membrane cofactor protein (CD46, MCP) in patients with systemic lupus erythematosus (SLE). (2/96)

Membrane cofactor protein (MCP, CD46) is a cell surface complement regulatory protein which acts as a cofactor for the factor I-mediated cleavage of the activated complement components C3b/C4b. To evaluate the clinical usefulness of serum soluble CD46 as a marker of disease activity in patients with SLE, serum levels of sCD46 were measured by ELISA, using two MoAbs (M160 and M177), each of which recognized two different epitopes on CD46 molecule in SLE, other autoimmune diseases and healthy controls. Serum sCD46 levels in active SLE patients (30.5 +/- 14.1 ng/ml) were significantly higher than those of inactive SLE (5.8 +/- 7.1 ng/ml; P = 0.0003), rheumatoid arthritis (14.9 +/- 11.6 ng/ml; P = 0.0218), primary Sjogren's syndrome (12.3 +/- 11.6 ng/ml; P = 0.0039) and normal controls (7.3 +/- 3.6 ng/ml; P = 0.0005). The elevated serum sCD46 levels in active SLE patients significantly decreased from 30.5 +/- 14.1 ng/ml to 8.0 +/- 6.3 ng/ml after effective corticosteroid and immunosuppressant therapy (P = 0.018). Additionally, we found a significant negative association between increasing concentration of sCD46 and decreasing levels of CH50 in SLE (r = -0.598, P = 0.0009). These results suggest that sCD46 reflects in vivo activation of complement system and provides an additional useful serum parameter of active SLE.  (+info)

Monomeric complement-activating IgG paraproteins. (3/96)

Three patients presented a unique syndrome of recurrent panniculitis with an IgGkappa paraprotein and depletion of the early components of the classical pathway of complement. The IgGkappa paraproteins were monomers with a normal structure, and with no evidence for aggregation, as assessed by electron microscopy and ultracentrifugation. Both heavy and light chains were of normal molecular size (SDS-PAGE), and the paraproteins were not heavily glycosylated. However, the paraproteins from all three patients had unusual features that included abnormal behavior on gel filtration chromatography and a heavy chain of high pI. When analyzed by fast protein liquid chromatography (Superdex 200), elution of the paraproteins was retarded, particularly when the ionic strength was increased. This retardation was partially reversed in 20% alcohol, and fully reversed in 6 M guanidine-HCl. Neither anti-C1 inhibitor nor anti-C1q autoantibodies were found in any of the patients' sera. However, the paraproteins bound to the globular heads of C1q at normal ionic strength. They activated C4 in normal human serum, but not in C1q-deficient serum. Activation led to the formation of C1s-C1 inhibitor complexes. Taken together, the data suggest that the unusual paraproteins have the capacity to bind C1q, which then leads to activation of C1. The ability of these paraproteins to activate C1, in spite of their being soluble monomers, is likely to be related to their unique physicochemical features.  (+info)

Enhanced anti-inflammatory activity of a liposomal intercellular adhesion molecule-1 antisense oligodeoxynucleotide in an acute model of contact hypersensitivity. (4/96)

The anti-inflammatory activity of free and liposome-encapsulated oligonucleotide targeted against intercellular adhesion molecule-1 mRNA was investigated in a delayed type hypersensitivity model of acute inflammation in mice. Contact hypersensitivity reactions to 2, 4-dinitrofluorobenzene were monitored by measuring ear thickness and cellular infiltration, both of which were observed to be maximal 24 h after ear challenge. A murine-specific phosphorothioate oligodeoxynucleotide and various control sequences were each passively encapsulated into 100-nm diameter large unilamellar vesicles composed of egg phosphatidylcholine and cholesterol. All formulations were administered as a single-bolus injection into the tail vein approximately 15 min after initiating ear inflammation. Oligodeoxynucleotide dose was varied from 5 to 50 mg/kg and the extent of inflammation was assessed 24 h later. Mice treated with free oligonucleotide, empty vesicles, or encapsulated control sequences showed no measurable effect on ear swelling or cellular infiltration compared with untreated controls. However, mice that received the active sequence encapsulated in lipid vesicles exhibited near baseline levels of ear thickness and leukocyte infiltration, similar to that observed in mice treated with a topical corticosteroid. These data demonstrate the utility of liposome-encapsulated intercellular adhesion molecule-1 antisense oligonucleotide as a novel anti-inflammatory therapeutic.  (+info)

Susceptibility of Vibrio cholerae O139 to antibody-dependent, complement-mediated bacteriolysis. (5/96)

Volunteer studies with Vibrio cholerae O1 have shown that the best correlate of a vaccine's protective efficacy is its propensity to elicit serum bactericidal responses in its recipients. Attempts to detect such responses following infection with V. cholerae O139, however, have met with varying success. Using a tube-based assay which involves viable counting, we now report that strains of serogroup O139 can appear to be sensitive or resistant to a fixed concentration of complement in the presence of antibody, depending on assay conditions. Susceptibility to lysis is critically dependent on the availability of complement, but with O139 indicator strains this is not simply determined by the concentration of serum added to the reaction mix. The nature of the assay diluent and the concentration of indicator bacteria can also dramatically affect bactericidal end points, whereas such variables have minimal significance with O1 indicator bacteria. Although some laboratories use unencapsulated mutant strains to seek evidence of seroconversion following exposure to V. cholerae O139, this is not necessary, and our findings question the significance of capsule expression as a determinant of complement sensitivity when antibody is present. The medium used for growth of the indicator strain and the particular strain used appeared to be unimportant. Each of seven O139 isolates tested was found to be lysed by antibody and complement in our standard assay system, which allowed the detection of significant serum bactericidal responses in 9 of 11 cases of O139 disease.  (+info)

Isolation, characterization, and cloning of porcine complement component C7. (6/96)

Activation of the complement system through the classical, alternative, or lectin pathway results in the formation of the terminal complement complex. C7 plays an integral role in the assembly of this complex with target cell membranes. To date, only human C7 has been cloned and characterized; thus, in this study, we characterized the porcine complement component C7. Porcine C7 was isolated by affinity chromatography as a single glycoprotein with an approximate molecular mass of 90 kDa and 100 kDa under reducing and nonreducing conditions, respectively. The full-length porcine C7 cDNA was isolated, and the predicted amino acid sequence exhibited 80% identity with human C7 with conservation of the cysteine backbone and two putative N-linked glycosylation sites. Porcine C7 mRNA expression was detected in all tissues investigated, except polymorphonuclear and mononuclear leukocytes. Addition of purified porcine C7 restored the hemolytic activity of C7-depleted human sera in a dose-dependent manner. A functionally inhibitory mAb against porcine C7 attenuated the hemolytic activity of human, rabbit, or rat sera, suggesting an important conserved C7 epitope among species. These data demonstrate that porcine and human C7 are highly conserved, sharing structural and functional characteristics.  (+info)

Chronic low level complement activation within the eye is controlled by intraocular complement regulatory proteins. (7/96)

PURPOSE: To explore the role of the complement system and complement regulatory proteins in an immune-privileged organ, the eye. METHODS: Eyes of normal Lewis rats were analyzed for the expression of complement regulatory proteins, membrane cofactor protein (MCP), decay-acceleration factor (DAF), membrane inhibitor of reactive lysis (MIRL, CD59), and cell surface regulator of complement (Crry), using immunohistochemistry, Western blot analysis, and reverse transcription-polymerase chain reaction (RT-PCR). Zymosan, a known activator of the alternative pathway of complement system was injected into the anterior chamber of the eye of Lewis rats. Animals were also injected intracamerally with 5 microl (25 microg) of neutralizing monoclonal antibody (mAb) against rat Crry (5I2) or CD59 (6D1) in an attempt to develop antibody induced anterior uveitis; control animals received 5 microl of sterile phosphate-buffered saline (PBS), OX-18 (25 microg), G-16-510E3 (25 microg), or MOPC-21 (25 microg). The role of complement system in antibody-induced uveitis was explored by intraperitoneal injection of 35 U cobra venom factor (CVF), 24 hours before antibody injection. Immunohistochemical staining and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with Western blot analysis were used to detect the presence of membrane attack complex (MAC) and C3 activation products, respectively, in normal and antibody-injected rat eyes. RESULTS: Complement activation product MAC was present in the normal rat eye, and intraocular injection of zymosan induced severe anterior uveitis. The complement regulatory proteins, MCP, DAF, CD59, and Crry, were identified in the normal rat eye. Soluble forms of Crry and CD59 were also detected in normal rat aqueous humor. Severe anterior uveitis developed in Lewis rats injected with a neutralizing mAb against Crry, with increased formation of C3 split products. Systemic complement depletion by CVF prevented the induction of anterior uveitis by anti-Crry mAb. Intracameral injection of anti-rat CD59 (6D1), anti-rat MHC class I antigen (OX-18), anti-rat Ig (G-16-510E3), or MOPC-21 caused no inflammatory reaction. CONCLUSIONS: The results suggest that the complement system is continuously active at a low level in the normal eye and is tightly regulated by intraocular complement regulatory proteins.  (+info)

Complement regulatory activity of normal human intraocular fluid is mediated by MCP, DAF, and CD59. (8/96)

PURPOSE: To identify the molecules in normal human intraocular fluid (aqueous humor and vitreous) that inhibit the functional activity of the complement system. METHODS: Aqueous humor and vitreous were obtained from patients with noninflammatory ocular disease at the time of surgery. Samples were incubated with normal human serum (NHS), and the mixture assayed for inhibition of the classical and alternative complement pathways using standard CH(50) and AH(50) hemolytic assays, respectively. Both aqueous humor and vitreous were fractionated by microconcentrators and size exclusion column chromatography. The inhibitory molecules were identified by immunoblotting as well as by studying the effect of depletion of membrane cofactor protein (MCP), decay-accelerating factor (DAF), and CD59 on inhibitory activity. RESULTS: Both aqueous humor and vitreous inhibited the activity of the classical pathway (CH(50)). Microcentrifugation revealed the major inhibitory activity resided in the fraction with an M(r) >/= 3 kDa. Chromatography on an S-100-HR column demonstrated that the most potent inhibition was associated with the high-molecular-weight fractions (>/=19.5 kDa). In contrast to unfractionated aqueous and vitreous, fractions with an M(r) >/= 3 kDa also had an inhibitory effect on the alternative pathway activity (AH(50)). The complement regulatory activity in normal human intraocular fluid was partially blocked by monoclonal antibodies against MCP, DAF, and CD59. Immunoblot analysis confirmed the presence of these three molecules in normal intraocular fluid. CONCLUSIONS: Our results demonstrate that normal human intraocular fluid (aqueous humor and vitreous) contains complement inhibitory factors. Furthermore, the high-molecular-weight factors appear to be the soluble forms of MCP, DAF, and CD59.  (+info)

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

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

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

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

Hemolysis is the destruction or breakdown of red blood cells, resulting in the release of hemoglobin into the surrounding fluid (plasma). This process can occur due to various reasons such as chemical agents, infections, autoimmune disorders, mechanical trauma, or genetic abnormalities. Hemolysis may lead to anemia and jaundice, among other complications. It is essential to monitor hemolysis levels in patients undergoing medical treatments that might cause this condition.

Hemolytic anemia is a type of anemia that occurs when red blood cells are destroyed (hemolysis) faster than they can be produced. Red blood cells are essential for carrying oxygen throughout the body. When they are destroyed, hemoglobin and other cellular components are released into the bloodstream, which can lead to complications such as kidney damage and gallstones.

Hemolytic anemia can be inherited or acquired. Inherited forms of the condition may result from genetic defects that affect the structure or function of red blood cells. Acquired forms of hemolytic anemia can be caused by various factors, including infections, medications, autoimmune disorders, and certain medical conditions such as cancer or blood disorders.

Symptoms of hemolytic anemia may include fatigue, weakness, shortness of breath, pale skin, jaundice (yellowing of the skin and eyes), dark urine, and a rapid heartbeat. Treatment for hemolytic anemia depends on the underlying cause and may include medications, blood transfusions, or surgery.

Hemolysins are a type of protein toxin produced by certain bacteria, fungi, and plants that have the ability to damage and destroy red blood cells (erythrocytes), leading to their lysis or hemolysis. This results in the release of hemoglobin into the surrounding environment. Hemolysins can be classified into two main categories:

1. Exotoxins: These are secreted by bacteria and directly damage host cells. They can be further divided into two types:
* Membrane attack complex/perforin-like proteins (MACPF): These hemolysins create pores in the membrane of red blood cells, disrupting their integrity and causing lysis. Examples include alpha-hemolysin from Staphylococcus aureus and streptolysin O from Streptococcus pyogenes.
* Enzymatic hemolysins: These hemolysins are enzymes that degrade specific components of the red blood cell membrane, ultimately leading to lysis. An example is streptolysin S from Streptococcus pyogenes, which is a thiol-activated, oxygen-labile hemolysin.
2. Endotoxins: These are part of the outer membrane of Gram-negative bacteria and can cause indirect hemolysis by activating the complement system or by stimulating the release of inflammatory mediators from host cells.

Hemolysins play a significant role in bacterial pathogenesis, contributing to tissue damage, impaired immune responses, and disease progression.

Hemolytic agents are substances that cause the destruction or lysis of red blood cells, leading to the release of hemoglobin into the plasma. This process is known as hemolysis. Hemolytic agents can be classified into two categories: intrinsic and extrinsic. Intrinsic hemolytic agents are present within the body, such as enzymes or antibodies, while extrinsic hemolytic agents come from external sources, like certain medications, chemicals, or infections. Hemolysis can result in anemia, jaundice, and kidney damage if not properly managed.

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

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

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

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

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

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

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

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

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

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

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

Hemolytic anemia, autoimmune is a type of anemia characterized by the premature destruction of red blood cells (RBCs) in which the immune system mistakenly attacks and destroys its own RBCs. This occurs when the body produces autoantibodies that bind to the surface of RBCs, leading to their rupture (hemolysis). The symptoms may include fatigue, weakness, shortness of breath, and dark colored urine. The diagnosis is made through blood tests that measure the number and size of RBCs, reticulocyte count, and the presence of autoantibodies. Treatment typically involves suppressing the immune system with medications such as corticosteroids or immunosuppressive drugs, and sometimes removal of the spleen (splenectomy) may be necessary.

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

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

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

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