In Vivo Activity of Lymphocytes Sensitized In Vitro by Antigen-Fed Macrophages: Inhibition of Lymphoma Growth

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Abstract
In previous studies, we have shown that macrophages fed with radiation leukemia virus could induce primary in vitro sensitization of lymphocytes which could be measured by their cytotoxic activity against target cells. In the present study, we tested the in vivo influence on tumor growth of such lymphocytes. We found that macro-phage-mediated sensitized lymphocytes could protect mice against tumor growth if injected into normal recipients four days prior to challenge with lymphoma cells. The protective function of such lymphocytes was not affected by their irradiation, but no protection occurred in sublethally irradiated recipients. This indicated that the sensitized lymphocytes did not inhibit tumor cell growth directly but recruited an effector protective response in the recipient mice. This protective activity was different from the one elicited by lymphocytes which had been sensitized directly against cells carrying antigens cross-reacting with RadLV. The protective activity of the directly sensitized lymphocytes was radiosensitive and was probably mediated by their direct cytotoxic activity against tumor cells.