EFFECT OF MODERATE EXERCISE ON PROLIFERATIVE RESPONSES OF PERIPHERAL-BLOOD MONONUCLEAR-CELLS

We studied the effects of 30 minutes of exercise on T lymphocyte count s and proliferative responses of peripheral blood mononuclear cells (P BMC) in 25 runners. Exercise resulted in a T lymphocytosis in the imme diate post-exercise period in all subjects (p<0.001), and reduced CD4/CD8+ ratios in 22/25 subjects (p=0.001). The change was due primarily to a 2.2-fold increase in CD8+ cells (p<0.001). Exercise also reduced PBMC mitogenic responses to phytohemagglutinin (PHA) in 13/14 subject s (p=0.049), and to pokeweed mitogen (PWM) in 11/14 subjects (p=0.022) , but not to concanavalin A. Postrun sera from 5 of 6 subjects-inhibit ed PHA but not PWM responses of resting autologous PBMC with normal CD 4+/CD8+ ratios (p less-than-or-equal-to 0.05): indomethacin and monocy te depletion blocked the serum inhibition (p=0.003, p=0.0006, respecti vely). We conclude that post-exercise suppression of mitogenic respons es to PHA is due to the release of a serum factor(s) capable of induci ng prostaglandin synthesis by circulating monocytes, whereas exercise- induced suppression of PWM responses depends primarily on the reversal of CD4+/CD8+ ratios.