The hybridoma technique of Kohler and Milstein was used to raise a monoclonal antibody against human neutrophils it has been found to inhibit neutrophil chemotaxis and degranulation. The antibody has been termed NCD 1. Incubation of 12 micrograms of NCD 1 with neutrophils (2 X 10(6)), followed by incubation with cytochalasin B and stimulation with either C5a, fMet-Leu-Phe, or soluble aggregated immunoglobulin, resulted in the inhibition of lysosomal enzyme release. The inhibition was not cytochalasin B dependent, since lysosomal enzyme release induced by opsonized zymosan or opsonized sheep erythrocytes was also inhibited, even in the absence of cytochalasin B. NCD 1 had no affect on enzyme release induced by the calcium ionophore A23138 or by phorbol myristate acetate. The antibody also inhibited neutrophil chemotaxis to zymosan-activated plasma and fMet-Leu-Phe. By contrast, superoxide production stimulated by phorbol myristate acetate, opsonized zymosan, or fMet-Leu-Phe was not affected by NCD 1. Similarly, uptake of 51Cr-labeled opsonized sheep erythrocytes into neutrophils was resistant to the effects of the antibody. NCD 1 Fab fragments did not inhibit lysosomal enzyme release or chemotaxis, althugh binding to the neutrophil surface was demonstrated by immunofluorescence. NCD 1 F(ab')2 fragments behaved analogously to the whole antibody. Binding of both fMet-Leu-[3H]Phe or 125I-soluble aggregated immunoglobulin to the cells was not inhibited by the antibody, which implied that NCD 1 was inhibiting some post-ligand binding event.