FcγRIIA-mediated spreading is Syk dependent. FcγRIIA transgenic platelets (2 × 10⁷/mL) were allowed to spread on coverslips coated with fibrinogen (100 μg/mL) for 45 minutes in the presence of PP2 (20 μM), PRT318 (5 μM), thrombin (0.1 U/mL), IV.3 fragment antigen-binding fragments (10 μg/mL), or vehicle (n = 3, **P < .01, ***P < .005).