Interleukin-2 production and activity in aged humans.

Peripheral blood mononuclear cells (PBMC) from aged humans were found impaired in their ability to mount T mitogen induced proliferative responses and NK cell activity. The production of IL-2 in response to PHA has also been found decreased in the aged subjects. When the data from IL-2 production and cellular responsiveness of aged and young groups were pooled for regression analysis, a significant correlation was found both for mitogenic responses and NK activity. The reduced proliferative responses and NK cell activity can be enhanced by exposing them to exogenous IL-2. However, they were not fully reconstituted to the levels achieved in PBMC of the young subjects supplemented in vitro with IL-2. This would indicate that the reduced cellular responsiveness in aging may be related both to a defect of IL-2 receptor expression on T cells of aged subjects and to an impairment in the endogenous IL-2 synthesis in the aged individuals.