Functional Analysis of Lymphocytes Infiltrating into Tumors Undergoing Rejection

Subcutaneous injection of 10? syngeneic gliosarcoma (T-9) cells is enough to kill Fisher rats within 2 months. Fisher rats can be induced to have a resistance to T-9 cells by surgical removal of the tumor and repeated immunization of MMC-treated T-9 cells. Histopathological analysis of implanted T-9 tumor tissue revealed a massive accumulation of mononuclear cells in the tumor tissues of immune rats which were rejecting syngeneic T-9 tumors, whereas very few mononuclear cells were found in the tumor tissues of non-immune rats. Mononuclear cells found within the regressing tumor of immune rats were identified mostly to be T cells and two-thirds of these T cells were Ly2 positive and very few macrophages, B cells and T cells with the helper phenotype were found. In contrast, only a few mononuclear cells were found within the growing tumor in nonimmune rats. They were identified to be a mixture of macrophages and T cells and a few Ly2 positive cells. Cytofluorographic analysis of infiltrating mononuclear cells demonstrated that a subpopulation of separated cells reflected histopathological patterns of various cell populations in situ. These mononuclear cells were found to be cytotoxic against T-9cells, whereas splenocytes and PBL from the same immune rats did not show cytotoxicity against T-9 cells in terms of ??Cr release assay. The results in in vitro ??Cr release assay was comfirmed by Winn assay showing that the tumor was rejected only when T-9 cells were implanted into normal Fisher rats along with lympho cytes from a regressing tumor of immune rats. Cell depletion studies revealed that Ly2 positive cells were important for rejecting tumor cells