Natural cell-mediated cytotoxicity in mice against non-lymphoid tumor cells and some normal cells

Lymphocytes from normal mice were found to have cell-mediated cytotoxicity, in a short-term 51Cr release assay, against a variety of non-lymphoid tumor cells as well as against lymphomas. Some of the non-lymphoid tumors were as susceptible to natural cytotoxicity as the standardly used lymphoid lines. Some tissue culture cell lines and in vivo passaged tumor lines were susceptible to lysis, as were some primary virus-induced lymphomas. Tumor which arose in nude mice, which have high levels of natural cytotoxic activity, were all resistant to lysis. In addition to the susceptibility of transformed cells to natural cell-mediated cytotoxicity, some untransformed cultured cells and cells from normal tissues were targets for this mechanism. Low levels of cytotoxicity were seen with normal thymus cells, bone-marrow cells, and short term cultures of macrophages, whereas normal spleen and lymph-node cells were completely resistant to lysis. These results indicate a broader spectrum for mouse natural cell-mediated cytotoxicity reactivity than has been previously recognized.