The influences of a whole body irradiation on the host immune system in mice

The influence of a whole body irradiation in mice was studied. Marked depression of the absolute lymphocyte count in the spleen and the peripheral blood was observed within 24 hour, with 300 rad. The count began to recover on day 4 in the spleen and completely recovered in about 4 weeks in the spleen and the peripheral blood. Incorporation of [3H]-TdR in the splenolymphocytes was reduced on day 1 postirradiation, however, the rate of [3H]-TdR-labeled cells per number of splenolymphocytes increased temporarily on day 1 and 4 postirradiation and, later, recovered quickly. Labeling index was enhanced only on day 4 postirradiation. In the case of the relative radiosensitivity of B lymphocytes, measured by antibody formation against SRBC, plaque-forming capacities were observed when antigens were injected into mice before or after irradiation. The capacities were extremely suppressed in each experimental groups. Cytotoxic activities against VX2-carcinoma cells were examined by microcytotoxicity assay. The activities increased more than 3 fold, both before immunization and on day 15 postirradiation, suggesting that B lymphocytes in antibody formation against SRBC were more radiosensitive than cytotoxic T lymphocytes against xenogeneic cells. Transfusion of splenolymphocyted labeled with [3H]-TdR was observed on day 4, which appeared to compensate for that of [51Cr]-labeled one. When [51Cr] labeled T lymphocytes were transfused intravenously, trapping and negative trapping of the lymphocytes were observed in spleen and in peripheral blood, respectively. (Ueda, J.)