Human neutrophils (PMN) express a heterodimeric receptor that has ligand binding specificity for the Arg-Gly-Asp (RGD) sequence within many adhesive proteins. A monoclonal antibody, B6H12, which binds to this receptor, inhibits both RGD-mediated ligand binding and stimulation of IgG-mediated phagocytosis by fibronectin, fibrinogen, vitronectin, von Willebrand's factor, and collagen type IV. By several criteria this receptor is neither a known very late antigen, a known cytoadhesin (gp IIb/IIIa-vitronectin receptor), nor a member of the LFA-1, Mac-1, p150,95 group of integrin receptors. Ligand binding via this receptor is rapidly inactivated by products of the myeloperoxidase-hydrogen peroxide-halide system of PMN. We conclude that this receptor, for which we propose the name leukocyte response integrin, is a signal-transducing molecule on PMN which may have a significant early role in modulation of PMN function at inflammatory sites.