GMP-140 is a 140-kDa granule membrane glycoprotein localized to the alpha-granules of platelets and the Weibel-Palade bodies of endothelial cells. Expression of GMP-140 on the activated cell surface has been shown to mediate the adhesion of thrombin-activated platelets to neutrophils and monocytes and the transient adhesion of neutrophils to endothelium. In contrast, fluid-phase GMP-140 strongly inhibits the CD18-dependent adhesion of tumor necrosis factor alpha-activated neutrophils to endothelium suggesting that GMP-140 can also serve an anti-adhesive function. In the present report, it is demonstrated that fluid-phase GMP-140 which exists predominantly as a tetramer binds to a single class of high affinity receptor on neutrophils and HL60 cells. Binding of 125I-labeled GMP-140 to neutrophils and HL60 cells and the rosetting of neutrophils and HL60 cells by thrombin-activated platelets were inhibited by EDTA, excess unlabeled fluid-phase GMP-140, Fab fragments of an affinity-purified rabbit anti-GMP-140 antibody, and by the murine anti-GMP-140 monoclonal antibody, AK 4. Both neutrophil and HL60 GMP-140 binding and platelet rosetting were strongly inhibited by heparin, fucoidin, and dextran sulfate 500,000, were partially inhibited by dextran sulfate 5,000 and lambda- and kappa-carrageenan, but were not inhibited by chondroitins 4- and 6-sulfate. Since this sulfated glycan specificity is identical to that previously reported by us for GMP-140, the present results suggest that the sulfated glycan binding site and the neutrophil receptor binding site on GMP-140 are either identical or proximal.