Inhibition of agonist-induced granular secretion by Sema3A. Washed platelets were preincubated with the indicated concentrations Sema3A/Fc, and then activated with ADP (5 μM) or thrombin (0.5 U/mL). Granular secretion was assessed by FITC-CD62P and PE-CD63 binding to platelets, and percent binding against hIgG-treated platelets was calculated. Shown are mean ± SE of percent binding of 3 independent experiments. *P < .05; **P < .01.