VITAMIN-E IS AN IMPORTANT FACTOR IN T-CELL DIFFERENTIATION IN THYMUS OF F344 RATS

The effect of vitamin E (dl-alpha-tocopheryl acetate) on T cell differ entiation in thymus of F344 rats was examined in this study. The rats were divided into three groups: vitamin E-free, regular and high vitam in E groups and fed a diet containing various levels of vitamin E (0, 50, and 585 mg/kg diet) for 7 weeks. The number of thymocytes was sign ificantly lower in the vitamin E-free group relative to the regular gr oup. Although the proportions of both CD4(+)CD8(-) and CD4(-)CD8(+) T cells in thymocytes were significantly greater in the high vitamin E g roup, the proportion of CD4(+)CD8(-) T cells inversely decreased in vi tamin E-free group compared to that of the regular group. The ratio of CD4(+) CD8(-)/CD4(-)CD8(+) T cells increased in the high vitamin E gr oup (p < 0.01) and significantly decreased in the vitamin E-free group (p < 0.001) compared to that of the regular group. Although the marke d changes of T cell subsets were not seen in peripheral blood lymphocy tes (PBL), the ratio of CD4(+)CD8(-)/CD4(-)CD8(+) T cells was signific antly lower in the vitamin E-free group and significantly greater in t he high vitamin E group compared to that of the regular group. Product ion of interleukin (IL) 2 by thymocytes following the stimulation with Con A for 48 h increased about threefold in the high vitamin E group compared to the regular group. Conversely, thymocytes from rats fed th e vitamin E-free diet showed a significant decrease of IL2 production compared to that of the regular group. Prostaglandin E(2) (PGE(2)) pro duction from thymocytes was significantly lower in the high vitamin E group compared to that of the regular group, whereas thymocytes of rat s fed the vitamin E-free diet showed a significant increase of PGE(2) production compared to that of rats fed the regular diet. Furthermore, in vitro addition of indomethacin provided a restoration of IL2 produ ction from thymocytes of rats fed the vitamin E-free diet to the level of rats fed the regular diet. These results suggest that vitamin E pl ays an important role in T cell differentiation in thymus, which may b e related to the action of vitamin E as antioxidant.