PAF-mediated platelet adhesion to endothelial cells induced by FMLP-stimulated leukocytes.

N-formyl-methionyl-leucyl-phenylalanine (FMLP), but not leukotriene B4 (LTB4), induced a significant platelet adhesion to endothelial cell monolayer when polymorphonuclear leukocytes (PMNs) were present in vitro. Neither of FMLP and LTB4 had an effect on the platelet adhesion in the absence of PMNs. An antagonist of platelet-activating factor (PAF), WEB 2086 completely inhibited the platelet adhesion induced by FMLP, while indomethacin and AA-861 had no effect. These results suggest that PMN-dependent platelet adhesion to endothelial cells induced by FMLP is mediated by PAF, and that PAF plays an important role during cell-cell interactions among platelets, PMNs and endothelial cells.