PECAM-1 cross-linking inhibits GPVI- and thrombin receptor–stimulated platelet aggregation.

(A) Platelets were stimulated with Cvx at (i) 15 ng/mL and (ii) 62.5 ng/mL with and without first cross-linking PECAM-1, and aggregation responses were monitored by optical aggregation (arrow indicates the addition of Cvx). (B) Platelets were stimulated with thrombin at (i) 0.05 U/mL and (ii) 0.1U/mL with and without prior cross-linking of PECAM-1 (as described in “Materials and methods”). Platelet aggregation was monitored by optical aggregometry (arrow indicates the addition of thrombin). Treatment of platelets with isotype-matched control IgG before stimulation with Cvx (15 ng/mL) and thrombin (0.05 U/mL) is shown in A(i) and B(i), respectively. Data are representative of 3 separate experiments. PECAM-1 XL, PECAM-1 cross-linking.