Studies of T-lymphocytes in preleukemic disorders and acute nonlymphocytic leukemia: in vitro radiosensitivity, mitogenic responsiveness, colony formation, and enumeration of lymphocytic subpopulations.

Tritiated thymidine incorporation in a whole blood lymphocyte stimulation test (LST) and lymphocyte colony formation (CFU-L) from whole blood were measured following in vitro x-irradiation. Lymphocytes from patients with myelodysplastic disorders, acute nonlymphocytic leukemia, and patients at increased risk for leukemia because of their primary disease and/or cytotoxic therapy were found to be significantly more sensitive to in vitro x-irradiation than lymphocytes from clinically normal individuals. Cloning efficiencies and mitogenic responsiveness of patient lymphocytes were significantly depressed as compared to normal values. Using monoclonal antibodies to specific surface markers, quantitative abnormalities in lymphocytic subpopulations from myelodysplastic patients also were observed. These findings are suggestive of a defect at the T-cell level that may directly or indirectly affect hematopoiesis.