Prolonged increase in T-cell receptor (TCR) variant fractions of spleen T lymphocytes in pregnant mice after gamma irradiation

To investigate the relationship between the radiation-induced increase of T-cell receptor (TCR) defective variant fractions and physiological status such as pregnancy, C57BL/ 6N mice were irradiated with 3 Gy of gamma rays at various days of gestation, just before and just after pregnancy. While the highest level of variant fractions in spleen T lymphocytes appeared at 9 days postirradiation and resolved fairly rapidly for nonpregnant mice, the increased variant fractions for pregnant mice irradiated at 16.5 days of gestation reached a plateau at 14 days postirradiation and remained at high levels until 28 days after irradiation. Therefore, variant fractions 28 days postirradiation were measured to determine the overall effect of radiation on the kinetics of TCR variant fractions during gestation. There was no significant difference in the baseline TCR variant fraction between unirradiated nonpregnant and pregnant mice. TCR variant fractions after irradiation were about twofold higher in pregnant mice (from 10.5 days of gestation until delivery) than those in nonpregnant mice. Both gamma radiation and pregnancy caused a decrease in the proportion of na?ve T-cell subsets and an increase in TCR variant fractions of na?ve T cells. In addition, the prolonged postirradiation increase in the TCR variant fractions of pregnant mice was associated with an increase in serum progesterone level. Differences between pregnant and nonpregnant mice in the kinetics of postirradiation restoration of T-cell systems may be involved in producing the differences in residual TCR variant fractions of these mice.