Blood group antigens on plasma vWF after ABO major mismatched BMT. The reactivities of the recipient’s plasma vWF before and after (7 months) major mismatched BMT (patient S.Y. with type O and the donor with type A) against UEA-I (white) and anti-A MoAb (black) were measured using ELISA and normalized as the reactivity (A₄₉₀) of 6 U/dL (1 μg/mL) of vWF solution. The reactivities of plasma vWF from normal subjects with blood group O and A against UEA-I and anti-A antibody were also measured as a control. Data express the means ± SE (n = 3) for a patient and the means ± SD (n = 6) for a control.