title: Evidence for a C4b binding site on the C2b domain of C2.
abstract: We raised murine mAb against human C protein C2. The representative mAb 3A3.3 (IgG1 kappa) recognized an epitope on the C2b domain of C2, as determined by binding and inhibition of binding radioassays. The hemolytic activity of purified human C2 and of C2 in normal human serum was inhibited by the mAb. The rate of decay of the C3-convertase at 30 degrees C was not affected by the mAb. C2 binding to EAC4b was inhibited by intact IgG and the Fab fragment of the mAb; 50% inhibition required 1 microgram/ml of either. The data suggest the presence of a C4b-binding site on the C2b domain of C2 and that the mAb recognizes an epitope at, or adjacent to, this site. The C2b portion of the C2 molecule may be important in assembly of the classical pathway C3-convertase.
authors.affiliation: Department of Medicine, University of Alabama, Birmingham 35294.
authors.forename: T J
authors.initials: TJ
authors.lastname: Oglesby
authors.forename: M A
authors.initials: MA
authors.lastname: Accavitti
authors.forename: J E
authors.initials: JE
authors.lastname: Volanakis
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D001666:Binding Sites, Antibody; D002352:Carrier Proteins / Q000032:analysis*; D003175:Complement C2 / Q000276:immunology / Q000378:metabolism*; D050679:Complement C2b; D050577:Complement C3-C5 Convertases / Q000378:metabolism; D003169:Complement Inactivator Proteins; D006023:Glycoproteins; D006168:Guinea Pigs; D006461:Hemolysis; D006801:Humans; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D012756:Sheep
chemical_list: D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D003175:Complement C2; D050679:Complement C2b; D003169:Complement Inactivator Proteins; D006023:Glycoproteins; D050577:Complement C3-C5 Convertases