Binding of mAbs to huVWF, muVwf, and huVWFmuA1. Plasma from VWF^−/− mice expressing huVWFmuA1 (○), huVWF (●), or muVwf (■) was evaluated for binding with (A) mAb9, which blocks the interaction of human VWF with GPIIbIIIa; (B) mAb203, which blocks the interaction of human VWF with fibrillar collagens; and (C) mAb505, which also interferes with the interaction of human VWF with fibrillar collagen but is different from mAb203. The tested antibodies were immobilized on a microtiter plate, and plasma was added at different VWF concentrations. Bound VWF was revealed with an HRP-labeled anti-VWF antibody. Each graph represents the mean ± SEM of the absorbance at 490 nm from 3 independent experiments.