Monoclonal antibodies to factor IX: characterization and use in immunoassays for factor IX.

Monoclonal antibodies to factor IX have been characterized for potential use in purification of factor IX and for analysis of factor IX abnormalities seen in hemophilia B and other conditions. The properties of six monoclonal antibodies to factor IX are summarized in this report. Antibodies were selected for diverse reactions with factor IX and activated factor IX and which had been transferred to nitrocellulose. Two antibodies showed preference for the heavy chain of activated factor IX, one antibody showed preference for the intact factor IX molecule while three antibodies reacted with the heavy chain of activated factor IX and the intact factor IX molecule equally. Five monoclonal antibodies inhibited factor IX clotting activity. Two antibodies, most specific for factor IX by competitive binding assays, have proved to be useful in immunoassays for factor IX antigen in normal plasmas and in samples from hemophilia B patients.