Epidemiological studies on dietary habit and daily activity in the aged and study on anti-aging factors by using cellular immunity as an index

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1.T cell differentiation and maturation in thymus and vitamin E :Six weeks old, F344 rats were fed control or high vitamin E diet, which contained 10 times higher vitamin E (alpha-tocopherol nictonate) than control diet, for 7 weeks. Rats from the high vitamin E group showed the increases in the proportions of both CD4+CD8- and CD4-CD8+ T cells in their thymocytes. In adition, the increase of IL2 production and the decrease of PGE_2 were shown in thymocytes of rats fed the high vitamin E diet. Thymic epithelial cell (TEC) function was also increased by feeding of the high vitamin E diet. Especially, the binding of immature T cells to TEC was significantly increased by the high vitamin E diet, which was associated with the increased expression of ICAM.However, vitamin E had no effect on macrophage function (Negative selection) existing between thymic cortex and medulla. These results suggest that high vitamin E diet enhances T cell differentiation and maturation in thymus via both the increased TEC function (Positive selection) in thymic cortex and increased proliferation of muture T cells in thymic medulla.2.The decrease of cellular immunity with aging, vitamin E and exercise training :F344 rats were fed control or the high vitamin E diet for 12 months from young age (8 weeks old). Then, their splenocyte function (mitogenesis) was investigated. As a result, rats fed control diet showed the decreased proliferation of splenocytes with Con A or PHA.On the other hand, rats fed the high vitamin E diet showed a significant increase of splenocyte proliferation, which was almost the same as that of young rats (8 weeks old). This was associated with both the increase of splenic macrophage function and the increased susceptibility of splenic lymphocytes to mitogen by feeding high vitamin E diet. Furthermore, the decrease of cellular immunity with aging was also improved by exercise training.