| C2a | activated second component of complement |
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| C3 | third cervical nerve; third cervical vertebra; third component of complement |
| C3a | activated third component of complement |
| C4 | fourth cervical nerve; fourth cervical vertebra; fourth component of complement |
| C4a | activated fourth component of complement |
| complement cytolysis inhibitor | <protein> Vertebrate glycoprotein of uncertain function. Secreted as a 400 amino acid peptide, then cleaved to form two 200 amino acid peptides that are linked by a disulphide bridge. Synonym: complement associated protein, complement cytolysis inhibitor, glycoprotein III. (11 Jan 1998) |
|---|---|
| complement factor h | <chemical> A beta-globulin that binds to complement 3b and makes ic3b (inactivated complement 3b) susceptible to cleavage by complement factor I. Complement factor h also acts as an alternative pathway complement inhibitor by interfering with the binding of properdin factor b to c3b. Chemical name: Complement factor H (12 Dec 1998) |
| complement factor I | <enzyme> Serine proteinase that acts on ic3b (inactivated complement 3b) to cleave it into c3c and c3dg with the help of a trypsin-like proteolytic enzyme. Complement factor I was formerly called kaf, c3binf, or enzyme 3b inactivator. Registry number: EC 3.4.21.45 (12 Dec 1998) |
| complement fixation | <immunology> Binding of complement as a result of its interaction with immune complexes (the classical pathway) or particular surfaces (alternative pathway). (18 Nov 1997) |
| complement-fixation reaction | <immunology> Binding of complement as a result of its interaction with immune complexes (the classical pathway) or particular surfaces (alternative pathway). (18 Nov 1997) |
| complement-fixation test | An immunological test for determining the presence of a particular antigen or antibody when one of the two is known to be present, based on the fact that complement is "fixed" in the presence of antigen and its specific antibody. See: Bordet-Gengou phenomenon. (05 Mar 2000) |
| complement fixation tests | Serologic tests based on inactivation of complement by the antigen-antibody complex (stage 1). Binding of free complement can be visualised by addition of a second antigen-antibody system such as red cells and appropriate red cell antibody (haemolysin) 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. (12 Dec 1998) |
| complement-fixing antibody | Antibody that combines with and sensitises antigen leading to the activation of complement, which may result in cell lysis. Synonym: CF antibody, sensitizing substance. (05 Mar 2000) |
| complement haemolytic activity assay | Usual screening assay for complement. Dilutions of the serum to be tested are added to antibody-coated erythrocytes and the percentage of lysis is measured. The values are expressed by ch50, haemolytic complement units per milliliter, which is the dilution of serum required to lyse 50 percent of the erythrocytes in the assay. (12 Dec 1998) |
| complement inactivators | Serum proteins which act at key sites in the complement sequence to modulate or prevent the progression of the reaction. Absence of these factors leads to uncontrolled activation of the complement system with accompanying disease. (12 Dec 1998) |
| complement membrane attack complex | The assembly of complement plasma glycoproteins c5b, c6, c7, c8, and polymeric c9 as a group on biological membranes. The complex forms transmembrane channels which displace lipid molecules and other constituents, thus disrupting the phospholipid bilayer of target cells leading to cell lysis by osmotic leakage. The formation of the membrane attack complex is the terminal step in the complement cascade. (12 Dec 1998) |
| complement pathway, alternative | The complement activation sequence initiated by the activation of complement factor c3, which is triggered by the interaction of microbial polysaccharides and properdin without participation of an antigen-antibody reaction. (12 Dec 1998) |
| complement pathway, classical | The sequential activation of complement, initiated by antigen-antibody complex and the binding of complement factor c1q to the fc region of the antibody. (12 Dec 1998) |
| complement system | A group of more than 20 serum proteins, some of which can be serially activated and participate in a cascade resulting in cell lysis. (05 Mar 2000) |
| complement unit | The smallest amount (highest dilution) of complement that will cause haemolysis of a unit of red blood cells in the presence of a haemolysin unit. Synonym: alexin unit. (05 Mar 2000) |