Inhibition of platelet aggregation by Sema3A. Washed platelets preincubated with 20 μg/mL Sema3A/AP or AP were activated with the indicated concentrations of collagen (left column) or thrombin (right column). Platelet aggregation was monitored using a platelet aggregometer. Arrow indicates the addition of agonists. Shown are representative results of 3 independent experiments.