T Cell Potentiation in Normal and Autoimmune-prone Mice after Extended Exposure to Low Doses of Ionizing Radiation and/or Caloric Restriction

Summary In order to better understand the apparent physiologic up-regulation in response to low levels of potentially lethal insults, murine T lymphocytes were analysed for functional and phenotypic alterations after exposure to 0·005 Gy/day, 0·01 Gy/day and 0·04 Gy/day in groups of ad-libitum-fed and calorie-restricted mice. These studies were conducted in two strains of mice: the long-lived and immunologically normal C57B1/6 +/+ and the congenic short-lived immunologically depressed C57B1/6 lpr/lpr. Whole-body exposure to 0·01 Gy/day and 0·04 Gy/day for an extended period of 20 days was associated with an increase in splenic proliferative response and with shifts in the proportions of T cell subpopulations in the thymus and spleen of both strains. Caloric restriction independently altered functional activity and T cell subpopulations in the same direction as low dose rates of ionizing radiation. Although the dose-response augmentation in proliferative activity was similar in the two strains, observed alterations in thymic and splenic T cell subpopulations were clearly different, suggesting that different mechanisms were responsible for immune enhancement in each strain.