Expression levels of gpIb, P-selectin, CD154, and CD40 on platelets in human thrombi.

(A) Expression of CD154 and other platelet markers in intravitally formed thrombi. Consecutive serial cryostat sections of fresh venous thrombi were immunostained for the platelet-specific marker gpIb, the activation marker P-selectin, CD154, and CD40 by the APAAP technique. Shown is a characteristic result. (B) Time course of CD154 expression in thrombi generated in vitro. Thrombi were generated by addition of 0.2 U/mL thrombin to PRP and vortexing. After the indicated time periods, the thrombi were snap-frozen, and consecutive sections were immunostained for the expression of CD154 and other platelet markers. Signal obtained for CD154 is shown at 3 minutes, 1 hour, 2 hours, and 6 hours using the tyramide amplification system. The immunostaining patterns of gpIb, P-selectin, and CD40 did not change significantly over the time examined (not shown). In all experiments, counterstaining was performed with hematoxylin; original magnification was 600 ×.