Factor VIII Related Antigen in Normal Blood Platelets and in Platelets of Patients with von Willebrand’s Disease

Abstract

The presence of Factor VIII-related antigen (F VIIIRA) in haemostatic plugs was demonstrated by immunofluorescent techniques. Immunofluorescent studies of intact washed platelets incubated with rabbit antifactor VIII in suspension showed that most of the platelets did not stain, whereas a positive staining was obtained after disruption of the membranes after air-drying of a drop of the same platelet suspension on a glass slide. This suggested that F VIIIRA was localized inside the platelets. F VIIIRA was detected in the supernatant of washed platelet suspensions that had been lysed by freezing and thawing (4 ×). This platelet F VIIIRA could not be distinguished from plasma factor VIII in immuno diffusion studies and cross-immuno-electrophoresis using antinormal factor VIII and the antisera against the low ionic strength subunits of factor VIII. The concentration of F VIIIRA in normal platelets was about 60 times as high as the concentration in plasma. Normal concentrations of F VIIIRA were detected in blood platelets and in 13 out of 15 patients with Von Willebrand’s Disease. No F VIIIRA was detected in the plasma of these patients with Von Willebrand’s Disease. Blood platelet F VIIIRA of normal platelets and of platelets of patients with Von Willebrand’s Disease supported the Ristocetin aggregation of washed platelets.