IgG Antibodies Against Factor VIII in Normal Individuals

Previously, we found noninhibitory antibody against factor VIII in a hemophilic subject. We screened sera from normal and hemophilic individuals for the presence of similar antibodies. Sera from 18 normal individuals and 17 hemophilia A subjects were tested for the presence of factor VIII antibodies. We also tested two commercial immunoglobulin preparations for the presence of similar antibodies. Serum from two normal individuals were found to have IgG1 and IgG2 antibodies against factor VIII. The two commercial immunoglobulin preparations also contained IgG1 and IgG2 antibodies against factor VIII. Conclusions: Sera of apparently normal individuals contain antibodies to factor VIII with no inhibitory qualities. Such antibodies against factor VIII appear to be a common occurrence.