Stimulation of human granulocyte function by monoclonal antibody WEM-G1

From a panel of monoclonal antibodies (MAb) produced against purified human neutrophils, MAb WEM-G1 was selected for its ability to stimulate granulocyte function as assessed by the capacity to kill antibody-coated tumor target cells. MAb WEM-G1 bound to neutrophils and eosinophils and not to monocytes, lymphocytes, or erythrocytes, and thus identified a granulocyte differentiation antigen. It enhanced killing by both neutrophils and eosinophils in a dose-dependent fashion, with a range of effector-to-target ratios and dilutions of anti-target cell antibody. The effect of MAb WEM-G1 was additive with that of colony-stimulating factor (CSF-alpha). Similarly, the ability of neutrophils to exhibit enhanced cytotoxicity in the presence of WEM-G1 was increased by preincubation of neutrophils with CSF-alpha. Immunoprecipitation analysis showed that WEM-G1 identified a cell-surface protein on human neutrophils of approximate molecular weight 110,000. It is suggested that this structure is involved in regulation of the function of human granulocytes.