Role of Vitamin E in Immune System

Vitamin E is a potent antioxidant and has an ability to modulate host immune functions. This manuscript consists of six parts:(1) vitamin E deficiency and immunity, (2) vitamin E supplementation and immunity, (3) vitamin E and the decreased cellular immunity with aging, (4) vitamin E and T-cell differentiation in the thymus, (5) vitamin E and acquired immune deficiency syndrome (AIDS), and (6) vitamin E and the abnormal increase of host immune functions such as allergy and autoimmune diseases. In vitamin E deficiency most of the immune parameters show a downward trend, which is associated with increased infectious diseases and the incidence of tumors. In contrast, vitamin E supplementation has various beneficial effects on the host immune system. The decreased cellular immunity with aging or during the development of AIDS is markedly improved by the intake of a high vitamin E diet. In addition, vitamin E plays an important role in the differentiation of immature T cells in thymus. Vitamin E deficiency induces the decreased differentiation of immature T cells, which results in the early decrease of cellular immunity with aging in spontaneously hypertensive rats. Conversely, vitamin E supplementation induces a higher differentiation of immature T cells via increased positive selection by thymic epithelial cells, which results in the improvement of decreased cellular immunity in the aged. Furthermore, some reports have shown that vitamin E has an ability to modulate the development of allergy or autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus. Taken together, all of the evidence suggest that vitamin E is a potent vitamin for modulating not only decreased immunity shown in the aged but also abnormally increased host immune system in patients with allergy or autoimmune diseases.