Factor VIII (Antihemophilic Factor) and Factor V (Proaccelerin) Activity of Platelets.

Abstract

Serum of hemophilic patients contains larger amounts of prothrombin than normal serum. Elevated serum prothrombin is probably responsible for an apparently smaller deficiency observed when TGT is performed using hemophilic plasma, serum and phospholipidic compounds, as compared with that observed when normal serum is substituted in that system for hemophilic serum. Elevated prothrombin activity of hemophilic serum undoubtedly contributed to reduction of PAI; however, maintaining the system “hemophilic plasma-hemophilic serum” unchanged, values of PAI are much greater when hemophilic platelets are added than when normal platelets are used (Table I). Defective activity of platelets was not characteristic of a single patient nor was it confined to congenital conditions. As expected, hemophilic platelets added to normal plasma and serum showed no abnormality (Table I). It is concluded that activity of platelets is of plasmatic origin. The active factor cannot be completely removed by multiple washings, is stable in stored platelets and in lyophilized material, but appears heat labile (Table II).