Stabilization of the Antihemophilic Factor (VIII :AHF) by the Von Willebrand Factor (VIII :VWF): A Possible Model for Von Willebrand’s Disease
When compared with VIII:AHF in normal citrated plasmas, VIII:AHF activity showed increased lability at 37°C in the ‘late’ post-transfusion plasmas (VIII:AHF≫VIII:VWF) of a patient with von Willebrand’s disease, but not in the ‘early’ post-transfusion plasmas in which VIII:AHF~VIII:VWF. VIII:AHF was also labile in the baseline plasmas of 3 patients with von Willebrand’s disease in whom VIII:AHF≫VIII:VWF. In two of these patients the mobility of Factor VIII antigen (on crossed Immunoelectrophoresis) was increased. (VIII:AHF was not excessively labile in 4 other patients in whom VIII :AHF~VIII:VWF). In all of the above cases, VIII:AHF was stabilized by the addition of either purified von Willebrand factor or plasmas of patients with hemophilia, but not by plasmas of patients with severe von Willebrand’s disease. Thus, VIII:VWF may serve to stabilize VIII:AHF and this might explain the post-transfusion findings in von Willebrand’s disease.