Association of Factor VIII Procoagulant Activity with Factor VIII Related Antigen

Abstract

Using the technique of coagulation in an agarose gel following rapid two dimensional Immunoelectrophoresis, the relationship of factor VIII procoagulant activity (VIIIC) with factor VIII related antigen (VIIIRA) was studied in plasma from patients with von Willebrand's disease and carriers of haemophilia. In each case, VIIIC was closely associated with both the fast and slow moving forms of factor VIIIRA as demonstrated by the formation of fibrin in the clotting gel in a similar position to the precipitin arc in the antibody containing gel.Mixtures of small molecular weight VIIIC with no detectable antigen and factor VIIIRA devoid of clotting activity, from either (a) haemophilic plasma, (b) Dithiothreitol treated haemophilic plasma, (c) normal serum or (d) von Willebrand serum were also studied using this technique. The samples of VIIIC and antigen were either electrophoresed in tandem or mixed in a test tube immediately prior to electrophoresis and an aliquot placed in a single well. Again fibrin formation occurred in the clotting gel in a similar position to the immune precipate. There was no peak of fibrin formation when the VIIIC was electrophoresed alone. All types of factor VIIIRA tested appeared to have an affinity for factor VIIIC and appeared to be capable of acting as a carrier protein.