PHYSICAL-ACTIVITY AND IMMUNE SENESCENCE IN MEN

A cross-sectional survey examined whether habitual endurance exerciser s retained a higher level of T cell function than sedentary individual s in old age. Subjects, all male, comprised 17 elderly runners, 16 you ng, and 19 elderly controls (mean ages +/- SD: 63.8 +/- 3.3, 23.6 +/- 1.6, and 65.8 +/- 3.5 yr, respectively), whose resting blood samples s erved for the immunological tests. Compared with the young subjects, b oth elderly groups had lower circulating CD3(+) and CD8(+) cell-counts (P = 0.029, P = 0.001, respectively), with a trend to a higher CD4/CD 8 ratio, but higher percentages of activated CD3(+), and ''memory'' CD 4(+) and CD8(+) cells (all, P < 0.001). Proliferative responses to phy tohemagglutinin, pokeweed mitogen, and alloantigens were markedly redu ced in the elderly (P < 0.001, P < 0.001, and P = 0.024, respectively) . IL-2 production tended to be decreased in the elderly sedentary subj ects. However, natural killer cell activity and other cytokine product ion remained unchanged in the elderly sedentary subjects. Comparison b etween the active and sedentary elderly groups showed no differences i n circulating counts of immunocompetent cells. However, the active eld erly subjects demonstrated significantly greater proliferative respons es to phytohemagglutinin (P = 0.016) and to pokeweed mitogen (P = 0.01 1), and higher rates of IL-2 (P = 0.021), IFN-gamma (P = 0.015) and IL -4 production (P = 0.012). These results suggest that endurance traini ng in later life is associated with a lesser age-related decline in ce rtain aspects of circulating T cell function and related cytokine prod uction.