Effect of GPIb-receptor occupation by MoAb 6D1 on platelet adhesion to collagen type III at a shear rate of 1,600 s^-1. Orgaran anticoagulated whole blood (+dRGDW) was incubated with MoAb 6D1 at room temperature for 30 minutes. The blood was then prewarmed at 37°C for 5 minutes. After prewarming, a sample was drawn for flow cytometry analysis and immediately thereafter the perfusion runs were started. The amount of free GPIb (○) was determined by flow cytometry. The platelet coverage (•) is expressed as percent control (without MoAb 6D1). Data are obtained in three independent experiments with blood from three different donors (mean ± SEM, n = 3). * Significantly different from control.