VITAMIN E SUPPLEMENTATION INDUCES AN EARLY RECOVERY OF CELLULAR IMMUNITY DECREASED FOLLOWING X-RAY IRRADIATION

Abstract We have previously reported that vitamin E has an ability to enhance T cell differentiation in rat thymus. The aim of this study is to investigate whether T cell differentiation enhanced by vitamin E supplementation is effective in decreasing cellular immunity after X-ray irradiation in rats. Male Fisher rats, 4-weeks old, were fed control (50 mg vitamin E/kg diet) or high vitamin E diet (585 mg vitamin E/kg diet) for 4 weeks and then irradiated X-ray. On 2, 5 and 9 days after X-ray irradiation, rats were killed under anesthesia and their cellular immune functions were assayed. Vitamin E supplementation did not result in decreased thymic weights or change in the numbers of thymocytes and peripheral blood lymphocytes (PBL) following X-ray irradiation. In addition, proliferation of PBL with T cell mitogens, phytohemagglutinin (PHA) and concanavalin A (ConA), also decreased in both control and high vitamin E groups following X-ray irradiation. On the contrary, proliferation of bone marrow cells (BMC) was maintained much the same as pretreatment of X-ray irradiation in high vitamin E group even after X-ray irradiation compared to a significant decrease in the control group. The proliferation of thymocytes with PHA or ConA also showed an early recovery in high vitamin E, which was associated with not the production of interleukin 2 (IL2), T cell growth factors, but early recovery in the proportion of CD4 + CD8 + T cells in thymocyte. These results suggest that vitamin E supplementation accelerates the recovery of the X-ray irradiation-induced decrease in cellular immunity. The signs of accelerated recovery were enhanced T cell differentiation in thymus and the maintenance of bone marrow cell (BMC) proliferation during X-ray irradiation.