Effect of VWF-GPIb interaction blockers on shear-induced platelet aggregation and tyrosine phosphorylations in the presence of 2B-rVWF. Washed platelets (2.8 × 10⁸/mL) were submitted to high shear rates in the presence of 2B-rVWF (0.7 μg/mL) at 37°C without (–) or with (+) MoAb 6D1 (20 μg/mL) or MoAb 328 (20 μg/mL). Buffer indicates samples without 2B-rVWF. SIPA was measured in aliquots fixed by 1.25% paraformaldehyde and means ± SEM of 3 experiments are shown (A). Proteins were immunoblotted with antiphosphotyrosine MoAbs 4G10 and PY20 (B, top) or anti–phospho-FAK (B, bottom). Results are representative of 3 experiments.