Effect of anti-vWf monoclonal antibodies on vWf binding to platelets.

Antibodies (final concentration, 50 μg/mL) were included in assays measuring binding of ¹²⁵I-labeled vWf (1 μg/mL) to GP Ib-IX-V on washed platelets induced by (A) botrocetin (25 μg/mL), (B) jaracetin (25 μg/mL), or (C) ristocetin (1 mg/mL). Antibodies were preincubated with vWf for 5 minutes at 22°C before the addition of washed platelets (final concentration, 5 × 10⁸/mL). Specific binding was expressed as a percentage of maximal specific binding measured in the absence of antibody. Nonspecific binding was assessed in the presence of 50 μg/mL of the inhibitory anti-GP Ibα monoclonal antibody, AK2. Results are the mean of quadruplicate determinations, with standard deviation from the mean of ≤ 5%.