Intervention in the aging immune system: Influence of dietary restriction,dehydroepiandrosterone, melatonin, and exercise

The decline in immunologic function with age is associated with an increase in susceptibility to infections and the occurrence of autoimmune diseases and cancers, Hence, the restoration of immunologic function is expected to have a beneficial effect in reducing pathology and maintaining a healthy co ndition in advanced age. A number of therapeutic strategies have been emplo yed to intervene in the aging immune system, This article reviews the effec t of dietary restriction (DR), dehydroepiandrosterone (DHEA) treatment, mel atonin (MLT) therapy, and exercise on modulating the immune responses and r etarding/reducing immunosenescence, DR has been subject to intensive resear ch and is known to be the most efficacious means of increasing longevity, r educing pathology and enhancing immune function. The circulatory levels of the androgen ic hormone DHEA and the pineal hormo ne MLT decrease with increasing age, and this decrease has been correlated with the age-related decline in the immune system, Therefore, the observati on that immunosenescence is associated with low levels of DHEA and MLT has provided a rationale for therapeutic intervention. DH EA treatment and MLT therapy both exhibit immune-stimulatory actions and preliminary reports ind icate that hormonal (DHEA or MLT) substitution therapy reverses immunosenes cence in mice, Similarly, exercise in some studies has been shown to enhanc e the immune response, However, these findings have not been confirmed by o ther laboratories, Thus, at the present time, it is difficult to draw any d efinitive conclusions on the efficacy of DHEA, MLT, and exercise on reversi ng or restoring the aging immune system.