Short-term changes in the immune system of elite swimmers under competition conditions. Different immunomodulation induced by various types of sport.

This study was designed to investigate changes in the immune system of elite swimmers compared with well-conditioned age- and sex-matched controls in relation to a competition swim (field study). Furthermore, the aim was to reveal possible differences in immune system changes depending on the type of sport performed by comparing with an earlier study of similar design, from the same laboratory that tested elite runners in relation to a competition run. The swimmers were tested before, immediately after and 2 h and 24 h after a competition swim. Lymphocyte subsets (CD5, CD3, HLA-DR, CD4, CD8, CD19, CD3/CD16+56, CD57, CD18, CD16/CD122) all increased after the run, decreased to normal or subnormal levels after 2 h, and returned to normal after 24 h (absolute numbers). The findings were identical for the swimmers and the age- and sex-matched control group. No change in polymorphonuclear granulocyte migration was found. The lymphocyte proliferative responses decreased 2 h after the exercise. No changes were seen in plasma cytokine levels (interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha) in relation to exercise, but significantly lower baseline values for IL-6 were observed in the swimmers. An increase in total natural killer cell activity immediately after exercise, followed after 2 h by a decrease, was seen in both swimmers and controls. Finally, no complement activation was detected. Compared with an earlier study of elite runners, differences were seen in granulocyte chemotactic response, TNF-alpha plasma activity and the lymphocyte proliferative response to mitogen. These differences might be explained by the degree of immune system activation following muscle damage during exercise, inducing an increase in cytokines, which are known to activate and modulate both lymphocytes and granulocyte function. Our findings demonstrate identical exercise-induced, immune system changes in elite swimmers and well conditioned controls, and furthermore, the findings suggest that different types of sport performed at maximum intensity induce different immune system changes.

Lymphocyte redistribution in connection with physical activity in the rat.

Previous studies have demonstrated numerous immunobiological changes in connection with exercise. A decrease in peripheral blood mononuclear white cells (PBMC) 2 h after intense exercise has been shown. This lymphocytopenia in humans after exercise is thought to be of great importance regarding the morbidity to viral infection. We constructed an animal experimental set-up, previously published, to investigate the exercise-induced lymphocyte redistribution. The experimental set-up allowed us to draw blood from catheters implanted in the right carotid artery in rats. PBMC were isolated and labelled with In111 and reinfused before the exercise run on a treadmill to exhaustion. The runner and control rats were killed and dissection performed 1 h after the exercise. Tissue samples were weighed and measured in a gamma counter. Furthermore, blind microscopic examinations of selected tissues were performed to study a hypothesized accumulation of blood mononuclear cells in relation to muscle fibre lesions. We found that the total number of PBMC in the running rats was decreased (P = 0.018) and granulocytes increased, 1 h after the exercise (P = 0.028). Similar findings in humans in connection with physical activity have been observed. The percentage of total injected counts per minute per gram tissue (% c.p.m. g-1) showed significantly lower values in the liver and kidney from runners than from controls (P = 0.032 and P = 0.028). These findings might be the result of a visceral hypoflow in connection with exercise. Furthermore, a tendency to decreased % c.p.m. g-1 in the lungs were seen in the exercised rats (P = 0.083) indicating a possible redistribution from the lungs during the run. Light microscopy demonstrated an accumulation of PBMC around muscle fibre lesions, but there was no significant difference between runners and controls. Furthermore, no significant difference in % c.p.m. g-1 was found between working muscle groups in runner and control rats. In conclusion, the demonstration of the redistribution of PBMC from the liver and kidney in the exercised rats and the absence of any significant accumulation of PBMC in working muscles or other organs, do not explain the lymphocytopenia demonstrated here.

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.