Whole blood collected from AA, SS, and SSCKO mice (n = 6 – 9 per genotype) was evaluated for platelet counts using flow cytometry (A). Expression of platelet surface activated GPIIb-IIIa reported as mean fluorescent intensity (per cell) of activated GPIIb-IIIa (B), and percentage of platelets positive for activated GPIIb-IIIa (C) is shown. Data in (B) and (C) were normalized to percent of maximal activation induced by TGPRP. All data are presented as mean ± SEM. * P < 0.05, ** P < 0.01, *** P < 0.001. Abbreviations: MFI = mean fluorescence intensity; ADP = Adenosine 5’-diphosphate (20 µM), TGPRP = Thrombin Gly-Pro-Arg-Pro (2U/mL).