Leukocytosis following exercise is a well-described phenomenon of stress/inflammatory activation in healthy humans. We hypothesized that, despite this increase in circulating inflammatory cells, exercise would paradoxically induce expression of both pro- and anti-inflammatory cytokines and growth factors within these cells. To test this hypothesis, 11 healthy adult men, 18–30 yr old, performed a 30-min bout of heavy cycling exercise; blood sampling was at baseline, end-exercise, and 60 min into recovery. The percentage of leukocytes positive for intracellular cytokines and growth factors and mean fluorescence intensity was obtained by flow cytometry. Proinflammatory cytokines (IL-1α, IL-2, IFN-γ, and TNF-α), a pleiotropic cytokine (IL-6), and anti-inflammatory cytokines and growth factors IL-4, IL-10, growth hormone (GH), and IGF-I were examined. Median fluorescence intensity was not affected by exercise; however, we found a number of significant changes ( P < 0.05 by mixed linear model and modified t -test) in the numbers of circulating cells positive for particular mediators. The pattern of expression reflected both pro- and anti-inflammatory functions. In T-helper lymphocytes, TNF-α, but also IL-6, and IL-4 were significantly increased. In monocytes, both IFN-γ and IL-4 increased. B-lymphocytes positive for GH and IGF-I increased significantly. GH-positive granulocytes also significantly increased. Collectively, these observations indicate that exercise primes an array of pro- and anti-inflammatory and growth factor expression within circulating leukocytes, perhaps preparing the organism to effectively respond to a variety of stressors imposed by exercise. immunology; interleukin-6; growth hormone; intracellular Address for reprint requests and other correspondence: D. Cooper, Center for the Study of Health Effects of Exercise in Children, Dept. of Pediatrics, Bldg. 25, 2nd Floor, 101 The City Drive, Orange, CA 92868 (e-mail: email@example.com )
Journal of Applied Physiology – The American Physiological Society
Published: Apr 1, 2006
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