Search

Plasma samples were obtained from patients of two families with inherited combined deficiency of factor V and factor VIII and examined by coagulation and immunological methods for the presence of factor V and factor VIII related antigens. A deficiency of procoagulant factor V was confirmed in all patients although a factor V related antigen was consistently demonstrated in all plasma samples by an inhibitor neutralisation technique using a non precipitating rabbit antibody. A deficiency of procoagulant factor VIII was also confirmed in all patients and factor VIII related antigens were detected by inhibitor neutralisation using human antibody and by electroimmunoassay using a precipitating rabbit antibody. The amounts of factor V and factor VIII related antigens present in the patient’s plasma samples were similar to those found in normal human plasma. Ristocetin co-factor assay using washed, fixed human platelets was normal in all patients. The results suggest that inactive antigenic determinants of procoagulant factor V and factor VIII are present in the plasma of these patients and are consistent with the possibility that a common precursor of factor V and factor VIII is defective in these families.