β 3 integrins modulate fibrin structure on platelets. (A,C) Clotting was initiated on platelets with the addition of recalcified, normal, pooled PFP to lipidated TF (1:120 000, final), in the presence of 0.136μM control IgG (A) or the anti-b3 Fab abciximab (C). (B,D) Clotting was initiated on platelets with the addition of fibrinogen, calcium, and thrombin (2 mg/mL, 5mM, and 2nM, respectively), in the presence of 0.136μM control IgG (B) or abciximab (D). Three-dimensional projections (146 μm × 146 μm, xy) show clot architecture in 10-μm stacks at 0 to 10 μm from the cell surface. Each image is from 1 experiment, representative of 4 independent experiments. Darker areas show increased fibrin density. Arrows in panels A and B indicate increased fibrin density surrounding individual platelets. (E) Data (± SD) indicate mean fibrin network density from all experiments. *P < .004 versus corresponding control IgG