Blood group antigens on vWF extracted from renal veins and platelets. vWFs in the normal plasma (Pls) and in the extracts of veins and platelets (Plt) from the subjects with type A were captured with anti-vWF antibody on an ELISA plate. The concentration of vWF and the reactivity against anti-A MoAb was measured and normalized as the anti-A reactivity (A₄₉₀) of 6 U/dL (1 μg/mL) of vWF solution. Each value indicates means ± SD (n = 3 except for type A vein, n = 2).