Lymphocytotoxic T lymphocytes in a patient with B-chronic lymphocytic leukemia and pure red cell aplasia

The peripheral blood T cells of a hypertransfused patient with B-chronic lymphocytic leukemia and pure red cell aplasic were found to exhibit unusual spontaneous cytotoxic activity in vitro. The patient's E-rosette positive cells were cytotoxic for K562 (cultured human crythroleukemia cells) and allogeneic B and T lymphocytes freshly isolated from the peripheral blood of normal and CLL donors. They failed to kill autologous B cells, erythroid progenitors present in allogeneic bone marrow, and a number of cultured human tumor cells (Malme, CAKI) even after prolonged (36 h) co-culture. Peripheral blood T cells isolated from normal controls, other CLL patients, and hypertransfused individuals (n=13) (lid not exhibit spontaneous lymphocytotoxic activity. Circulating cytotoxic T cells having the ability to kill freshly isolated allogeneic lymphocytes have, heretofore, not been reported in humans. Our findings suggest that among this patient's peripheral blood T cells, there exists a subpopulation of lymphocytotoxic cells that closely resemble cytotoxic T cells generated in vitro after priming with allogeneic target cells. Although the lymphocytotoxic cells could have been induced in this patient by previous HLA-mismatched transfusions, it is possible they may have arisen spontaneously and underly the patient's erythroblastopenic state.