Vitamin E enhances the immune functions of young but not old mice under restraint stress

Young and old C57BL/6 male mice were given a diet containing a high dose of vitamin E (VE treatment) and its effect on the immune system was examined before and after the exposure to restraint stress. The VE treatment per se gave rise to a slight increase of splenic T cells in percentage and a significant enhancement of Con A response of spleen cells in young, but not in old mice. The VE treatment also resulted in the enhancement of production of IL-2 and IFNγ in young, but not in old mice. Restraint stress led to thymic involution in both young and old mice. This thymic involution was not ameliorated by the VE treatment. Percentage of splenic T cells and their mitogenic response decreased just after the stress, but soon rebounded over the control level. The VE treatment further enhanced the recovery after the stress in young mice, but on the contrary suppressed the recovery in old mice. The results in the present study suggested that the VE treatment was effective in the prevention of immunological decline of young mice before and after the exposure to the stress. On the other hand, such a preventive effect was not observed in old mice that were already in the depressed state of immunological functions.