Melatonin and the immune system in aging.

Aging is associated with a decline in immune function (immunosenescence), a condition known to correlate with increased incidence of cancer as well as infectious and degenerative diseases. Innate, cellular and humoral immunity all exhibit increased deterioration with age. Circulating melatonin decreases with age, and in recent years much interest has been focused on its immunomodulatory effect. Melatonin stimulates the production of progenitor cells for granulocytes and macrophages. It also stimulates the production of natural killer cells and CD4+ cells and inhibits CD8+ cells. The production and release of various cytokines from natural killer cells and T helper lymphocytes are enhanced by melatonin. Melatonin has the potential therapeutic value to enhance immune function in aged individuals.