Antibodies to Factor VIII: Specificity and Kinetics of Iso- and Hetero-antibodies in Hemophilia A

Time course inactivation of isologous and heterologous AHF preparations induced by anti-factor VIII antibodies from hemophiliacs followed two major patterns: one was consistent with a second-order reaction, the other more complex. The second-order type, characterized by a plateau of residual factor VIII activity occuring after 2-4 hr of incubation, was observed in the interaction of factor VIII with its corresponding and specific antibody. The complex type, showing a gradual decline of factor VIII activity following a rapid initial fall, was detected in antigen-antibody-reactions relying predominantly on cross-reactions. It is proposed that reactions of the second-order type reflect the formation of stable antigen-antibody complexes, while reactions of the complex-order type express a tendency to spontaneous dissociation of antigen-antibody complexes.