Antibody-directed phagocytosis of tumor cells is enhanced by il-1 p and m-csf in freshly isolated human monocytes or the new macrophage line kim

Antibody-directed phagocytosis is an important function of monocytes/macrophages. Ingestion of opsonûed microorganisms, red cells, and platelets has been extensively studied; the significance of such phagocytosis of tumor cells by monocytes/macrophages, however, has only recently been proposed by Munn et al. (J. Exp. Med. 172,231,90). In the present studies, freshly isolated monocytes and the new human macrophage line, KIM, were cultured for 4-7 days in the presence of 20 ng/ml of IL-I or 200 units/ml of M-CSF. Afterwards, they were incubated for 0, 4, and 18 h with neuroblastoma cells NMB-7and 5 ug/ml of specific antitumor antibody 14G2a. The target neuroblastoma cells had been prelabcled with the fluorescent cell linker PKH26-GL (red); monocytes or the macrophage line was stained with antiCD14/HLA-DR FITC (green). Tumor cell phagocytosis was analyzed by uptake of red-labeled target cells within green-labeled monocytes or macrophage KIM cells in the presence of antitumor antibody 14G2a in microscope and flow cytometry assay. The longer the incubation time, the more target neuroblastoma cells were taken up by monocytes/KlM cells. More phagocytosis was observed with monocytcs/KIM cells stimulated for 4-7 days with IL-I or M-CSF than with medium alone. Finally, monocytes or KIM cells also phagocytosed neuro-blastoma cells in the absence of 14G2a, albeit to a much lesser degree. The new KIM ceil line, which arose spontaneously from peripheral blood of an ostensibly normal donor, was confirmed as macrophage by surface phenotyping: CD4CDlla bc+CDl4+CD16 CDI8CD26+CD29CD32CD36'CD40+CD43+CD44TCD45CD54+CD58CD64CD 71CD74+CD88HLA-DRDQDP4HLA-ABCVCAM-rB7-l+B7-2ICAM-2 ICAM-3'. There is no detectable expression of T cell, B cell, or NK specific markers.