We have studied the spontaneous killing of B5(59) melanoma cells by Bacillus Calmette-Guérin (BCG)-elicited macrophages under strictly anaerobic conditions to investigate the role of oxygen in macrophage-mediated cytotoxicity. The number of melanoma cells capable of forming colonies after aerobic or anaerobic incubation with BCG-macrophages was used as the index of cytotoxicity. The BCG-macrophages killed melanoma cells regardless of the amount of oxygen present. The killing observed was proportional to the ratio of effector cells added; a ratio of 25:1 effector to target cells was required to achieve nearly 90% cytotoxicity both aerobically and anaerobically. This cytotoxicity was not dependent on a diffusible macrophage product nor on alteration of the medium by macrophages, since tumor cells incubated in the same culture medium, but not in contact with a mixed population of tumor cells and macrophages, were not killed. These results also indicated that macrophage-mediated cytotoxicity was dependent on macrophage-tumor cell contact. The mechanism responsible for the oxygen-independent cytotoxicity is unknown at present.
Bacillus Calmette-Guérin-activated murine macrophages kill syngeneic melanoma cells under strict anaerobic conditions.
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V H Freedman, T E Gorrell, C F Nathan, C S Copeland, S C Silverstein; Bacillus Calmette-Guérin-activated murine macrophages kill syngeneic melanoma cells under strict anaerobic conditions.. J Exp Med 1 July 1984; 160 (1): 94–107. doi: https://doi.org/10.1084/jem.160.1.94
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