LPS-induced platelet activation. (A) HMEC-1 cells were grown on glass slides and incubated with O157LPS for 1 hour at 37°C. Before perfusion, cells were washed and serum-free medium was added. Platelets were fluorescently labeled with quinacrine dihydrochloride (10 μM). PRP perfused over HMEC-1 incubated with O157LPS at lower shear rates (340 s^-1) showed multiple small aggregates of attached platelets. (B) Attachment increased at higher shear rates (500 s^-1). (C) Larger aggregates formed at 1500 s^-1. (D) PRP perfused over HMEC-1 cells that were not incubated with O157LPS. Preincubation of PRP with anti-human TLR4 (E) or anti-CD62 (F) inhibited binding between platelets and cell-bound LPS.