Factor VIII and Human Platelet Aggregation

Abstract

When highly purified human factor VIII was submitted to agarose gel chromatography in the presence of 0.5 M CaCl2, the procoagulant activity (low molecular weight factor VIII, LMW-F VIII) was separated from the void volume protein (Vo-VIII). Upon incubation of human factor VIII with purified neuraminidase, a very stable platelet aggregating activity developed in the Vo-VIII fraction, not in the LMW-F VIII part. The generated aggregating activity was apparently a property of the carrier protein for LMW-F VIII. Desialylated factor VIII retained its antigenic reactivity, its procoagulant or ristocetin cofactor properties and the capacity of its subunits to dissociate and recombine. Neuraminidase-treated human factor VIII, in contrast to intact bovine factor VIII or intact human factor VIII in the presence of ristocetin, did not induce aggregation of EDTA-platelet rich plasma, of congenitally afibrinogenemic platelet rich plasma, nor of washed platelets.