Epitope Specificity of Factor VIII Inhibitor Antibodies

SummaryAntibodies that inactivate factor VIII develop most frequently in patients with severe hemophilia A, and they present a serious complication in the therapy of such individuals. Most patients with inhibitors have two or more different antibodies capable of factor VIII inactivation in their plasma, as shown by assays in which several factor VIII domain fragments are tested for neutralization of the inhibitor activity. Such neutralization assays of 23 patient plasmas suggest that there are three common epitopes. These epitopes have been localized by several methods to the A2, A3, and C2 factor VIII domains.…