Tumor Cell Cytotoxicity by Granulocytes From Peripheral Blood of Tumor-Bearing Mice 2

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Abstract
Since previous findings by us indicated that tumor-specific cytotoxicity of macrophages was derived from ancestral colony-forming antecedent stem cells, we tried to determine if granulocytes derived from the same stem cells also possessed tumor-specific cytotoxicity. Our present findings Indicated that circulating granulocytes in tumor-bearing Inbred C3HeB/FeJ mice were cytotoxic to tumor cells and that the degree of cytotoxicity was equivalent to or greater than that of an equal number of cells from the mononuclear fraction of blood or from regional lymph nodes. Specificity of granulocyte cytotoxicity was confirmed by the observation that after 28 days of tumor growth, when both the immunizing and target cells were from a mammary carcinoma in inbred C3H mice. designated C3H tumor. cytotoxicity was 50%. If target cells were from a carcinoma produced by 3-methylcholanthrene instillation, MCF tumor, cytotoxicity was 9%. When both tumor and target cells were from an MCF tumor, cytotoxicity was 46% versus 5% when targ.t cells were from a C3H tumor. Addition of mononuclear cells from C3H tumor-sensitized hosts to MCF tumor-sensitized granulocytes failed to enhance cytotoxicity of the granulocytes. Granulocyte cytotoxicity was inhibited by serum from the tumor-bearing host. e.g., 67–14%. The findings suggested that granulocytes may play as important a role in the cell-mediated response of a host to Its tumor as do other effector cells that have received more attention i.e., lymphocytes and macrophages.