Studies of the human factor VIII/von Willebrand's factor protein. I. Comparison of the protein found in normal, von Willebrand's disease and hemophilia

tor protein was characterized in two unrelated patients with von Willebrand's disease in whom procoagulant and Factor VIII/von Willebrand factor antigen levels were normal. In both patients evidence of an abnor-mal protein was observed on crossed antigen-antibody electrophoresis. In one patient the Factor VIII/von Willebrand factor protein eluted from Sepharose 4B in a position and distribution identical to normal with normal levels of procoagulant activity and antigen. However, the partially purified Factor VIII/von Wil-lebrand factor protein had markedly reduced von Wil-lebrand factor activity in a ristocetin assay. In the sec-ond patient the peak of Factor VIII/von Willebrand factor protein, antigen, and procoagulant activity eluted from a Sepharose 4B column with an estimate