title: Use of antisera to the isolated alpha and beta subunits of C3 as probes to study functional sites present on particle-bound C3b but absent on native soluble forms of C3.
abstract: The effect of antisera to the isolated alpha and beta chains of C3 on certain C3b-dependent reactions has been studied. C5-mediated haemolysis of EAC1423b was inhibited preferentially by antiserum to the alpha chain, whereas antiserum to the beta chain inhibited the formation of C3bBb. The anti-beta chain antiserum also stabilised C3bBbP, and rendered the enzyme relatively resistant to accelerated decay in the presence of factor H. These and previous findings that anti-alpha and anti-beta IgG bind to restricted subsets of antigenic determinants on C3/C3b suggest that these antisera affect C3b function through the binding of antibodies to active binding sites exclusively exposed by bound C3b. The anti-alpha and anti-beta antibody probes are currently being further developed to verify this interpretation.
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000032:analysis*; D001665:Binding Sites; D003176:Complement C3 / Q000276:immunology*; D003179:Complement C3b / Q000378:metabolism*; D003602:Cytotoxicity, Immunologic; D000939:Epitopes; D007106:Immune Sera / Q000494:pharmacology*; D010446:Peptide Fragments / Q000276:immunology*; D011817:Rabbits; D011951:Receptors, Complement / Q000494:pharmacology; D013499:Surface Properties
chemical_list: D000954:Antigens, Surface; D003176:Complement C3; D000939:Epitopes; D007106:Immune Sera; D010446:Peptide Fragments; D011951:Receptors, Complement; C044257:factor H receptors; D003179:Complement C3b