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

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 inves tigate whether T cell differentiation enhanced by vitamin E supplement ation is effective in decreasing cellular immunity after X-ray irradia tion in rats. Male Fisher rats, 4-weeks old, were fed control (50 mg v itamin E/kg diet) or high vitamin E diet (585 mg vitamin E/kg diet) fo r 4 weeks and then irradiated X-ray. On 2, 5 and 9 days after X-ray ir radiation, rats were killed under anesthesia and their cellular immune functions were assayed. Vitamin E supplementation did not result in d ecreased thymic weights or change in the numbers of thymocytes and per ipheral blood lymphocytes (PBL) following X-ray irradiation. In additi on, proliferation of PBL with T cell mitogens, phytohemagglutinin (PHA ) and concanavalin A (ConA), also decreased in both control and high v itamin E groups following X-ray irradiation. On the contrary, prolifer ation of bone marrow cells (BMC) was maintained much the same as pretr eatment of X-ray irradiation in high vitamin E group even after X-ray irradiation compared to a significant decrease in the control group. T he proliferation of thymocytes with PHA or ConA also showed an early r ecovery in high vitamin E, which was associated with not the productio n of interleukin 2 (IL2), T cell growth factors, but early recovery in the proportion of CD4(+)CD8(+) T cells in thymocyte. These results su ggest that vitamin E supplementation accelerates the recovery of the X -ray irradiation induced decrease in cellular immunity. The signs of a ccelerated recovery were enhanced T cell differentiation in thymus and the maintenance of bone marrow cell (BMC) proliferation during X-ray irradiation.