Biosynthetic granulocyte-macrophage colony-stimulating factor enhances neutrophil cytotoxicity toward human leukemia cells

Purified biosynthetic (recombinant) human granulocyte-macrophage colony-stimulating factor (GM-CSF) enhances antibody-dependent cell-mediated cytotoxicity (ADCC) of human neutrophils toward human promyelocytic leukemia cells (HL-60), B-lymphoma cells, and human T-leukemia virus II-infected human B-lymphoblastoid cells. The stimulation of antibody-dependent cell-mediated cytotoxicity is rapid (less than an hour), occurs at picomolar concentrations of GM-CSF, and does not require the presence of GM-CSF during the killing reaction. Therefore, neutrophils may be targeted toward tumor cells by antibody and their tumoricidal activity enhanced by GM-CSF in vitro. These results suggest that GM-CSF may have therapeutic utility in cancer therapy by increasing the number and activity of effector cells directed toward tumors by receptors to the immunoglobulin Fc fragment.