In Vitro Cytotoxicity of Mouse Macrophages Activated by Coculture with Syngeneic Sarcoma Cells

Abstract

Normal resident peritoneal macrophages from C3D2 (C3H/Tif .times. DBA/2) F1 mice were activated in vitro by culturing with semisyngeneic tumor cells. The tumor cells originated from a methylcholanthrene-induced sarcoma (MCIM) growing in vivo in ascites form. Macrophage-mediated cytotoxicity was evaluated after 5 days of in vitro culture, using 5 different target cells. Semisyngeneic (L 929), allogeneic (B16 melanoma), and xenogeneic (HeLa [human cervical carcinoma]) tumor cell lines and normal allogeneic fibroblast cell lines (3T3, 3T6) were tested. The morphology and kinetics of the cytotoxicity reaction were studied by scanning electron microscopy and compared with release of radioactivity from 14C-thymidine-labeled target cells. The activated macrophages were able to kill the semisyngeneic, allogeneic, and xenogeneic tumor cell lines tested under conidtions that did not affect normal fibroblasts. The requirement for T cells during activation of the macrophages was also tested. The cytotoxicity decreased markedly when T cells were removed from the macrophage cultures before activation or when macrophages from nude mice were used in the experiments.