title: Antibody density on rat red cells determines the rate of activation of the complement component C1.
abstract: It is a common observation that there is variability in the rate of activation of C1, the first component of complement, when bound to immune complexes. The cause of this variation has been investigated with experiments designed to assess separately the effect of antibody, antigen and C1 density. Using 125I-labeled C1 and a rat monoclonal antibody specific for the class I antigen, it has been found that the rate of activation is primarily dependent on antibody density on the cell surface and not on antigen or C1 density. This finding supports the suggestion that direct contact between the C1r2C1s2 subcomponent of C1 and antibody may be required for potentiation of C1 activation.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D003166:Complement Activating Enzymes / Q000276:immunology; D003167:Complement Activation; D003172:Complement C1 / Q000276:immunology*; D015923:Complement C1r; D003173:Complement C1s; D004306:Dose-Response Relationship, Immunologic; D004910:Erythrocyte Membrane / Q000276:immunology*; D007700:Kinetics; D046911:Macromolecular Substances; D051381:Rats
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D003172:Complement C1; D046911:Macromolecular Substances; D003166:Complement Activating Enzymes; D015923:Complement C1r; D003173:Complement C1s