Identification of six functional clotting factor VIII:C epitopes by analysis of cross-reactive public idiotypes in murine monoclonal VIII:C inhibitors.
Six factor VIII:C epitopes which can elicit clotting factor inhibitory antibodies were demonstrated by analysis of public idiotypes of murine monoclonal anti-VIII:C inhibitors. Anti-idiotypic immunoradiometric assays were developed with rabbit antibodies to murine VIII:C inhibitors: Synbiotics, Hybritech, C7F7 and RFF-VIIIC/8. Crossreactions among 10 murine monoclonal antibodies (MoAbs) to VIII:C were tested, showing 6 functional and immunospecific VIII:C epitopes. One epitope on the C-terminal, 80,000 dalton fragment of VIII:C was identified with cross-reaction among 3 MoAbs (Synbiotics, Chemicon, and IB3). Another unique site on this same fragment was recognized with C7F7. Two MoAbs (RFF-VIIIC/6 and RFF-VIIIC/8) defined another site with cross-reactive idiotypes on the N-terminal, 90,000 dalton fragment. Hybritech MoAb identified a fourth functionally distinct site to which no other cross-reacting MoAbs bound. A fifth functional locus was defined with RFF-VIIIC/2 which reacted with an N-terminal site (distinct from the RFF-VIIIC/6 X RFF-VIIIC/8-defined site). A sixth functional locus was recognized with RFF-VIIIC/5 which reacted with a C-terminal site (distinct from the Synbiotics/Chemicon/IB3-defined site but possibly near the C7F7-defined site). RFF-VIIIC/10 identified a non-functional locus on the middle region of VIII:C. These MoAb-based assays resolve six sites to which high-titered inhibitors are directed and offer a path to further study the immunoregulation of human anti-VIII:C inhibitors.
D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000276:immunology*; D003429:Cross Reactions; D000939:Epitopes / Q000032:analysis*; D005169:Factor VIII / Q000037:antagonists & inhibitors / Q000276:immunology*; D006467:Hemophilia A / Q000097:blood / Q000276:immunology; D006801:Humans; D007130:Immunoglobulin Idiotypes / Q000276:immunology; D051379:Mice; D011817:Rabbits
D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D000939:Epitopes; D007130:Immunoglobulin Idiotypes; D005169:Factor VIII