Expression and structure of platelet CD40.

(A) Unstimulated platelets were analyzed by flow cytometry for expression of CD40 and gpIb. (B) Washed platelets were stimulated for the indicated time periods with 0.2 U/mL thrombin and analyzed for expression of CD154 and CD40. The background signal obtained with the isotype control antibody is shown in black. (C) CD40 was immunoprecipitated from lysates of platelets and PBMCs with mAb G28-5 and detected by Western blotting with a CD40-specific antiserum. Unstim indicates unstimulated.