CHEMOATTRACTANT-INDUCED CHANGES IN SURFACE EXPRESSION AND REDISTRIBUTION OF A FUNCTIONAL LIGAND FOR P-SELECTIN ON NEUTROPHILS

Adhesion between platelets and neutrophils is mediated through the int eraction of P-selectin on activated platelets with a carbohydrate-cont aining structure on neutrophils, and occurs under both static and shea r conditions. Recent studies using flow chambers have shown that neutr ophils become activated after binding to surface-adherent platelets ex pressing P-selectin. The objective of the present study was to investi gate the effect of such activation on the interactions of platelet P-s electin with its ligand on neutrophils. Flow cytometric analyses using P-selectin chimeras revealed that activation induced a rapid and mark ed reduction in chimera binding, with levels of binding decreased by 7 1% after 15 minutes of stimulation with the chemotactic agent, FMLP. U sing a visual assay of platelet-neutrophil rosetting, we showed that t he P-selectin ligand was translocated and clustered at the uropod of n eutrophils following the shape changes and polarization induced by che motactic stimulation. Activated neutrophils bound to surface-adherent platelets also displayed the clustering of P-selectin ligand at the ur opod, and these neutrophils detached from the platelets when a shear s tress (2 dynes/cm(2)) was applied through the adhesion chamber. These results indicate that chemotactic stimulation of neutrophils induces c hanges in the surface expression and distribution of a biologically re levant ligand for P-selectin, and that these changes might influence t he adhesive interactions occurring between neutrophils and activated p latelets. (C) 1996 by The American Society of Hematology.