Effects of scFvs on thrombus formation in whole blood. (A) Anticoagulated whole blood, preincubated with scFvs 10B12 (circles), 1C3 (squares), or a control 2D4 (anti-HLA A2; triangles) was passed over collagen III–coated coverslips at low (300s^–1; open symbols) or high shear (1600s^–1; closed symbols). Data are expressed as a percentage of surface coverage in the absence of scFv at each shear rate and represent the mean ± SD for 3 separate donors. (B) Micrographs of surface coverage obtained at high shear in the presence of 0, 3, or 50 μg/mL scFv 10B12. Individual platelets are seen as the smaller dots in the right-hand boxes.