Monoclonal antibody characterization of a chymotrypsin-like molecule on neutrophil membrane associated with cellular activation

Abstract

Monoclonal antibody 1-15 (Ab 1-15), is a murine anti-human neutrophil (PMN) IgG1 that inhibits PMN effector responses to N-formyl-met-leu-phe (FMLP) and phorbol myristate acetate. In this study, the effects of Ab 1-15 on PMN membrane-related functions were characterized: Ab 1-15 inhibited PMN superoxide (O2-) response to FMLP by 60% (P < 0.005) without effect on the onset or duration of O2- production. This inhibition of O2- response was associated with a significant inhibition of PMN chymotrypsin-like, but not trypsin-like, protease activity. Cell fractionation studies indicated the presence of an Ab 1-15-inhibitible, chymotryptic neutral protease activity in PMN membranes. In studies of Ab 1-15 effects on membrane-related second messenger pathways, Ab 1-15 augmented both FMLP- and isoproterenol-induced intracellular cAMP accumulation, whereas α-chymotrypsin decreased PMN cAMP response to these stimuli. Our data suggest that the function-inhibiting, anti-PMN monoclonal Ab 1-15 defines a PMN chymotryptic enzyme on the membrane surface that is involved in regulation of two membrane-related functions, O2- generation and cAMP generation.