HETEROGENOUS EFFECTS OF EXOGENOUS LYMPHOKINES ON LYMPHOPROLIFERATION OF ELDERLY SUBJECTS

Although the ability of peripheral blood mononuclear cells of a population of elderly subjects (mean age 85.3) to proliferate in response to the T cell mitogens phytohemagglutinin (PHA) and concanavalin A (Con A) is significantly reduced compared to young subjects (mean age 24.7), the response of the elderly subjects is heterogenous. While 47% of the elderly subjects responded at about half the level of young controls, 15% responded at less than 20% the level and the remaining 38% responded comparably to young controls. Similar heterogeneity was observed in lymphokine production. However, there was no significant correlation between the level of proliferative response and production of either interleukin 2 (IL-2) or interferon gamma (IFN-g). In an effort to further explore the role of lymphokines in the decreased proliferative response of elderly subjects, various concentrations of exogenous IL-2 and/or IFN-gamma were added at the initiation of the mitogen stimulated cultures. Similar increases in both the level of response and the number of subjects demonstrating an increase was observed for both young and elderly subjects upon addition of either IL-2 or IFN-gamma. However, addition of a combination of IL-2 and IFN produced more pronounced effects in the elderly subjects. Approximately 1/3 of the elderly subjects who demonstrated decreased PHA-induced proliferation doubled their PHA induced proliferative response upon addition of a combination of lymphokines. The amounts of IL-2 and IFN-gamma required for this increase varied for each individual. These results indicate that lymphokines can restore the proliferative response of only some elderly subjects and that the concentrations of lymphokines required for this effect need to be determined for each individual.