Non-T-cell-mediated cytotoxicity in mice with tumors induced by Moloney murine sarcoma virus (M-MuSV). II. Granulocyte-mediatd cytotoxicity against autochthonous target cells isolated from M-MuSV-induced tumors.

Experiments were performed in A/Sn and A/WySn mice to determine the specificity, organ distribution, and further characteristics of the small non-T-cells that infiltrate Moloney murine sarcoma virus (M-MuSV)-induced tumors and are capable of killing the autochthonous M-MuSV-infected tumor target cells. Continuous bovine serum albumin density gradient separation proved to be the most effective method of enriching the cytotoxic cells. Increase in cytotoxic activity, measured by both the 51Cr release assay and the microcytotoxicity test, paralleled the increase in the proportion of polymorphonuclear leukocytes in mice bearing M-MuSV-induced tumors also contained myeloperoxidas-positive cytotoxic effector cells. The cytotoxic activity appeared to be nonspecific. Various mouse tumor lines as well as allogeneic fibroblasts were sensitive to these effector cells. The only target cell type not affected was the syngeneic fibroblast. In addition to the tumor mass, cytotoxic cells were found in the bone marrow, blood, and spleens of mice bearing M-MuSV-induced tumors. Only bone marrow cells from normal mice exhibited cytotoxic activity. Thus cells of the myelopoietic series may be important in fighting M-MuSV-induced tumors by way of their direct cytotoxic effects on the infected cells.