Differential leukocytosis and lymphocyte mitogenic response to acute maximal exercise in the young and old

Despite the increasing use of exercise in the elderly as a means of improvi ng muscle function, little is known regarding the effects of exercise on th e senescent immune system. Purpose: The purpose of this study was to determ ine the effects of acute maximal exercise on blood leukocyte numbers, leuko cyte subsets, and the T cell mitogenic response in the elderly, Methods: Pr eviously sedentary elderly (N = 33, 65.3 +/- 0.8 yr) and young (N = 14, 22. 4 +/- 0.7 yr) subjects participated in a modified Balke maximal exercise tr eadmill test. Venous blood samples were collected pre-, immediately post-, and 20 min postexercise. Blood was analyzed for leukocyte counts, leukocyte subsets via immunofluorescence, and whole blood mitogenesis in response to various doses of mitogens. Results: Whereas (V) over dot O-2max was lower in the elderly, maximal RQ, age-predicted heart rates, and times to fatigue were not different, indicating that both groups achieved relative maximal exercise intensity. There were significant exercise-induced leukocytoses in both the elderly and young made up largely of a lymphocytosis and neutroph ilia. The magnitude of the leukocytosis was lower in the elderly and failed to return to pre-exercise levels by 20 min postexercise. Acute maximal exe rcise increased CD8(+) (153% vs 112% in young and old, respectively) and CD 4(+) (57% vs 22% in young and old, respectively)T cells when measured immed iately postexercise. By 20 min postexercise, concentrations in the young we re not significantly different from baseline, whereas CD8 cell number was s till elevated in the old. The elderly had significantly higher percentages of memory (i.e., CD45RO(+)) and significantly lower percentages of naive (i .e., CD45RA(+)) CD4 and CD8 T cells pre-exercise, and the young and old rec ruited approximately equal numbers of CD8+ naive and memory cells to the bl ood in response to exercise. In contrast, the aged recruited significantly fewer numbers of CD4(+) naive and transitional (CD45RA(+)RO(+)) cells. At m ost doses of Con A and PHA, the lymphoproliferative response was lower in t he elderly subjects even though they had significantly higher numbers and p ercentages of CD3(+) cells. Interestingly, immediately postexercise, young (but not old) subjects demonstrated reduced proliferative ability on a per CD3(+) cell basis. Conclusions: These data indicate that several blood leuk ocyte responses to maximal exercise stress are similar in the young and the old. However, the elderly demonstrate a less resilient leukocytosis and a different lympho-proliferative response following acute maximal exercise.