There are few facts regarding the biology of aging in man and other animals. It is known that as we age we progressively loose the intensity of our cell mediated immune reactions. We have recently described a prostaglandin producing suppressor cell in human peripheral blood and have shown that increased activity of this cell is responsible for the depressed mitogen response in lymphocytes from patients with Hodgkin's Disease. More recently we have found that lymphocytes from healthy old people are more sensitive ( by approximately two orders of magnitude) to the inhibiting effects of prostaglandin E2. Blockade of prostaglandin production in mitogen stimulated cultures causes an approximately fourfold greater increase in 3H-thymidine incorporation in lymphocytes from healthy old people than in lymphocytes from young controls. In this present study, we wish to extend these observations to a larger group of elderly individuals and to follow these subjects with periodic retesting over time in an attempt to correlate suppression of cellular immunity and/or sensitivity to prostaglandins with survival. Secondly, we wish to study the effect of in vivo indomethacin administration to old people on their humoral and cellular immune response. Third, we will investigate other systems in the body, in which prostaglandins act as feedback inhibitors, to determine if tissues other than lymphocytes become more sensitive to inhibition by prostaglandin with aging. Fourth, we wish to continue our studies on the mechanisms of inhibition of prostaglandins and other putative mediators of suppression on the mitogen response.