Platelet aggregation, granule recreation, and α_IIbβ₃ activation. Platelets (200 × 10⁹/L) were isolated from WT or PTPN22^−/− mice and stimulated with CRP (0.1 μg/mL) (A), collagen (0.25 μg/mL) (B), thrombin (0.01 U/mL) (C), or ADP (5 μM) (D) followed by analysis of platelet aggregation and ATP release (indicator of dense granule secretion) (except ADP stimulation) in a Model 700 Lumi-Aggregometer (Chrono-log Corporation). P-selectin expression (α-granule secretion) (presented as the % positive staining of anti-CD62P antibody) (E), ADP secretion (F), α_IIbβ₃ activation (presented by JON/A binding) (G), calcium mobilization (H), and cytokines released in response to CRP stimulation (I). Data are shown as mean ± standard error (n = 3-5; unpaired t test or two-way analysis of variance). *P < .05, **P < .01, ***P < .001. M-CSF, macrophage colony-stimulating factor; RFU, relative fluorescence units.