Cytotoxic effects in vitro by lymphoid cells from specifically tolerant animals.

Mice of strain A were made tolerant to cells from (A×CBA)F mice by neonatal injection of spleen cells. Lymphoid cells from tolerant animals carrying (A×CBA)F skin grafts for 1–6 months were competent to cause destruction of both (A×CBA)F and CBA fibroblast target cells in tissue culture in the presence of PHA. Normal A lymphoid cells were cytotoxic to both targets, whereas (A×CBA)F lymphocytes did not kill the syngeneic F targets, but were effective against the CBA fibroblasts. Lymphocytes from H-2 incompatible strains were cytotoxic to both target cell genotypes. These experiments demonstrate that the A lymphocytes in animals toleratn to (A×CBA)F were effective in causing destruction of the target cells, indicating that PHA-induced cytotoxicity by incompatible cells is independent of specific immunological recognition processes.