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

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Abstract
Radiation treatment of breast cancer patients (45.0 Gy [gray]) 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 a reduced number of T cells. Antigen and mitogen stimulation, MLC [mixed lymphocyte culture] reactivity, pokeweed mitogen (PWM)-induced Ig production in vitro, and different cytotoxic functions decreased. Depletion of monocytes 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. Suppressor T 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.