Platelet procoagulant activity in FcRγ^-/- platelets. (A) Platelets isolated from wild-type (C57BL/6) (▪) or FcRγ^-/- (▦) mice were stimulated with the indicated agonists for 5 minutes, and thrombin generation was measured in a prothrombinase assay as described in “Materials and methods”; n = 5. ^*P < .05 relative to wild-type platelets. (B) Quantification of the platelet population with high levels of annexin V binding in FcRγ^-/- and wild-type platelets following stimulation with the indicated agonist for 5 minutes; n = 3. ^*P < .01 relative to wild-type platelets.