Effect of radiation therapy and in vitro x-ray exposure on lymphocyte subpopulations and their functions

Radiation treatment of breast cancer patients (45.0 Gy) profoundly affected the peripheral blood lymphocytes. The number of these cells was markedly reduced with non-T-cells being more extensively depleted than T-cells immediately after radiation. The long-lasting lymphopenia, on the other hand, was mainly due to reduced number of T-cells. Antigen and mitogen stimulability, MLC reactivity, pokeweed (PWM)-induced immunoglobulin (Ig) production in vitro, and different cytotoxic functions decreased. Depletion of lymphocytes largely restored the radiation-depressed lymphocyte reactivity. The effects of in vitro exposure of blood lymphocytes to x-rays were similar to those seen after radiotherapy. Non-T-cells and T-cells with Fc-receptors for IgG were relatively radiosensitive. This latter observation agreed well with demonstrated increase of PWM-induced Ig synthesis after in vitro exposure to x-rays. T-suppressor cells defined by monoclonal antibodies were, however, radioresistant. The cytotoxic functions were reduced. No correlations were found between the pretreatment immunological status or the extent of radiation-induced immunological suppression, respectively, and prognosis.