CYTOTOXICITY OF HUMAN MACROPHAGES FOR TUMOR-CELLS - ENHANCEMENT BY HUMAN-LYMPHOCYTE MEDIATORS

Human macrophages, derived from peripheral blood monocytes, acquire enhanced cytotoxicity for human target cells after incubation in mediator-rich supernates from antigen-stimulated lymphocytes. Maximum cytotoxicity was observed after 24 h incubation in mediators. In comparison to normal macrophages, mediator-activated macrophages were cytotoxic to 5 of the 6 malignant cell lines tested but had no effect on 5 nonmalignant cell lines. In 20 experiments with 1 target ([human breast carcinoma] SK-BR-3), mean cytotoxicity was 23 .+-. 2.7% and with another target ([human prostate adenoma] MA-160), was 29 .+-. 3.4%. Macrophages became cytotoxic after 8 h incubation with mediators and the enhanced cytotoxicity persisted for at least 40 h after the lymphocyte mediators were removed. The hypothesis that macrophages, activated by antigen-induced lymphocyte mediators, can contribute to the host resistance to tumor growth in man was supported.