CYTOTOXICITY BY NONIMMUNE ALLOGENEIC LYMPHOID CELLS

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Abstract
Nonimmune lymphoid cells were capable of causing cytotoxicity of H-2 incompatible mouse tumor cells in vitro in the presence of Phytohemagglutinin, whereas syngeneic cells were not. Semisyngeneic and X-irradiated (1500-3000 R) F1 hybrid lymphoid cells were cytotoxic for target cells derived from one of the parental strains. Parental nonimmune and X-irradiated lymphoid cells damaged hybrid target cells. One component of cytotoxicity was not related to an induction of a primary immune response in vitro, since F1 hybrid cells are not capable of reacting immunologically against parental type target cells. Cytotoxicity was probably caused by target cell confrontation with antigenically and/or structurally incompatible lymphoid cells. The demonstration that iso-antibodies produced in the target strain and directed against the allogeneic lymphod cells specifically suppressed cytotoxicity was noted. Isoantibodies reacting against some but not all of the antigenic determinants of the lymphoid cells differentiating them from the target cells did not suppress cytotoxicity. The specific suppression of cytotoxicity by specific isoantibodies against the lymphoid cells supports the allogeneic inhibition concept.