Coated platelet formation following dual agonist stimulation is greatly decreased in FcRγ^-/- platelets. Platelets isolated from wild-type (C57BL/6) (▪) or FcRγ^-/- (▦) mice were stimulated with the indicated agonists for 7 minutes. (A) The percentage of platelets with high surface P-selectin expression was measured by flow cytometry with FITC anti-CD62P. (B) Coated platelet formation was evaluated as the percentage of platelets with high fibrinogen, low PE-JON/A binding as indicated in Figure 2B; n = 3. ^*P < .05 relative to wild-type platelets. (C) FcRγ^-/- platelets stained with FITC-antifibrinogen and PE-JON/A and analyzed by 2-color flow cytometry. Dashed boxes indicate the activated and coated platelet populations.