Effect of anti-vWF and anti-GP Ibα antibodies on vWF binding to platelets.

(A) Effect of the anti-vWF monoclonal antibodies (10 μg/mL, final concentration) on specific binding of ¹²⁵I-labeled vWF (1 μg/mL) to washed platelets (5 × 10⁷) in the presence of either 1 mg/mL (final concentration) ristocetin (▪) or 2.5 μg/mL botrocetin (■).7 The labeled vWF was incubated with the cells for 30 minutes at 22°C, after pre-incubating the platelets with the antibody for 5 minutes. Maximum binding was measured in the absence of antibody, and nonspecific binding was determined in the absence of modulator, in parallel assays. Data are the mean of triplicate determinations (± SEM). (B) Effect of anti-GP Ibα monoclonal antibodies (10 μg/mL, final concentration) on specific binding of¹²⁵I-labeled vWF to washed platelets in the presence of either ristocetin (▪) or botrocetin (■) using the same assay as described in the legend to panel A.9,10