Immune senescence and adrenal steroids: immune dysregulation and the action of dehydroepiandrosterone (DHEA) in old animals.

Immune senescence is characterized by dysregulation of the immune system. The disorder occurs during old age and is manifested by an increased production of autoantibodies and a decreased production of antibodies to most foreign antigens. These events seem to reflect an altered ratio of activity between the CD5+ and CD5- B cell subsets. Likewise, there is dysregulation of cytokine production with an increased production of IL-4, IL-5 and IL-6 associated with a decreased production of IL-2. This appears to reflect an altered ratio of activity between the Th1 and Th2 cell subsets. Dehydroepiandrosterone (DHEA) is one of the three principal adrenal steroids; its serum concentration declines with age. Recent results suggest that in vitro culture of lymphocytes, from aged donors, with DHEA or in vivo treatment of old mice with DHA sulphate results in the augmentation of the antibody response to foreign antigens and a reversal in the dysregulated cytokine production by T cells. Thus, a decline in one of the three principal adrenal steroids is associated with age-associated changes in the immune system. Some of these changes can be reversed by exposure to DHEA.