Vitamin E enhances T cell differentiation through increased epithelial cell function in rat thymus

Abstract

This study was designed to elucidate the mechanism on increased T cell differentiation in thymus following vitamin E supplementation and discussed on the changes of epithelial cell (TEC) and macrophage functions in thymus following vitamin E supplementation. Thymic epithelial cells isolated by panning method from thymocytes of rats fed the high vitamin E (500 IU α-tocopherol nicotinate/kg) diet for 7 weeks increased the proportion of CD4+CD8- T cells in thymocytes. In addition, when thymic epithelial cell line IT45-R1 was pretreated with vitamin E for 24 h and then incubated with immature T cells for 48 h, they also enhanced the proportion of CD4+CD8-T cells in thymocytes. On the contrary, the supernatant of IT45-R1 treated in vitro with vitamin E for 24 h did not have any effect on the proportions of T cell subsets in thymocytes. Furthermore, in vitro treatment with vitamin E significantly enhanced the binding capacity of TEC to immature T cells. The expression of adhesion molecule, ICAM-1, on the membrane of TEC was also greatly increased by high vitamin E diet. However, in vitro incubation with macrophages isolated from rats fed the regular or high vitamin E diet did not induce a significant difference in the changes of T cell subsets in immature T cells. These results suggest that vitamin E enhances T cell differentiation through the increase of not macrophage but TEC function in thymus, which is associated with the increased binding capacity of TEC to immature T cells via increased expression of ICAM-1.