Characterization of surface-bound C3 or C9 on platelets and on platelet-derived microparticles. Incubation of platelet-rich plasma (A) or whole blood (B) with Stx2 or O157LPS induced deposition of C3c, C3b, iC3b, C9neo, or C5b-9 on the surface of platelets (A) and to a lesser degree on platelet-derived microparticles (B). Data are expressed as median ± SD (n = 5 experiments). C3 or C9 deposition on platelets (in platelet-rich plasma) or platelet microparticles (in whole blood) incubated with agonists was compared with that in unstimulated samples. *P < .05; **P < .001. NS indicates not significant.