Involvement of PF4 and RANTES in monocyte arrest stimulated by platelet supernatants. Monocytic MM6 cells were left untreated (A,C) or incubated with supernatants of human platelets (10⁶/μL) activated with thrombin (0.5 U/mL) for 5 minutes (B,D). The surface binding of RANTES (A,C) and PF4 (B,D) was analyzed by flow cytometry in comparison with isotype control (filled histograms). MM6 cells stimulated with platelet supernatants for 5 minutes and perfused on activated HUVECs, and the number of firmly adherent monocytes was determined after accumulation for 5 minutes (E). Data represent mean ± SEM of 4 independent experiments (*P < .05 as indicated).