Ectopic expression of FcγRIIa potentiates platelet activation. (A) Representative aggregation tracings for WT FcγRIIa^neg vs FcγRIIa^pos platelets in response to low- and medium-dose CRP. (B) Quantitation of platelet aggregation (mean percent aggregation ± SEM, n = 4 per group). (C) Representative photograph of thrombin-induced clot retraction. Washed platelets from WT or FcγRIIa transgenic mice were resuspended in plasma at a final concentration of 3 × 10⁸/mL. Thrombin (0.2 U/mL) and CaCl₂ (1mM) were added to initiate clot retraction. Images were taken 30 minutes later. (D) Quantification of plasma volume remaining following removal of the fibrin clot 30 minutes after initiation of the reaction. Results represent the mean ± SEM (n = 4 per group, **P < .01). Note that the presence of the FcγRIIa transgene enhances fibrin clot retraction at this early time point.