Effect of physical exercise on cytokines and lymphocyte subpopulations in human peripheral blood.

To examine the effect of intensive physical exercise on interleukin 2 (IL-2), tumor necrosis factor alpha (TNF alpha) and lymphocyte subsets, eleven elite and well-conditioned runners were tested in relation to a five-kilometer race. IL-2 was significantly decreased (p less than 0.01) immediately after the exercise and significantly increased after 24 hours (p less than 0.05), compared to the pre-exercise values taken at steady state. TNF alpha was significantly increased after 2 hours (p less than 0.05), and returned to habitual values after 24 hours. In the steady state at rest, elevation of HLA-DR+ cells was observed in all runners compared with control subjects (p less than 0.05), indicating a persistent activation of lymphoid cells. In connection with exercise a significant increase in NK cells (CD16+) was observed (p less than 0.01). The T-helper/T-suppressor (CD4+/CD8+) ratio was significantly reduced in connection with physical activity (p less than 0.01). In seven runners the ratio was reduced to a value of less than one. This decrease was observed immediately after the exercise, followed by increased ratios 2 hours later (p less than 0.01), due to oppositely directed quantitative changes of the CD4+ and CD8+ cell populations. After 24 hours the ratios returned to habitual levels. Furthermore, we confirmed an increase in the total number of granulocytes in connection with exercise (p less than 0.01), and observed a decrease in absolute numbers of lymphocytes two hours after exercise (p less than 0.01). We emphasize the importance of obtaining information about physical activity within the previous 24 hours before measuring white blood cell parameters.