Lymphocyte subsets during the first hours and days after a 2.5 h running test.

After a 2.5 h running test on eight healthy young males the lymphocyte subsets in peripheral blood were analyzed by flow cytometry. The analysis was carried out immediately post-exercise, after a 1 h and 3 h interval as well as a one day, a two day and five day interval. Lymphocyte subpopulations were also measured in five control subjects who did not exercise. Compared with the pre-exercise level the total lymphocyte and T-cell count was decreased 1 h and 3 h after the run and one and two days after exercise (p less than 0.01). The absolute number of monocytes and B-lymphocytes fell significantly (p less than 0.01) on the first and second day after exercise. No consistent change of helper-/suppressor-inducer T-lymphocytes (CD4+) and cytotoxic-suppressor T-cells (CD8+) cells was observed immediately after exercise. One and 3 h later, however, the absolute number of both cell types dropped below pre-exercise values (p less than 0.01). The decrease of the CD8+ cells was more pronounced, causing an increase of the CD4+ to CD8+ ratio (p less than 0.01). Among the CD4+ cells only the Leu 8+ subpopulation showed a relative increase 1 h after the exercise (p less than 0.01) while the Leu 8- population remained unaffected. 1 h and 3 h after the end of the run there was a significant fall of the absolute number and percentage of natural killer cells (Leu 7+) and cytotoxic T-cells (CD8+ Leu 7+) (p less than 0.01). These cells remained low during the first and second day after the exercise (p less than 0.01). In the control subjects the changes of cell counts for all cells examined were much smaller than in the runners. The results indicate that strenuous and prolonged exercise causes a delayed redistribution of lymphocyte subpopulations with a reduction of lymphocytes and particularly of natural killer and cytotoxic cells beginning 1 h after the exercise followed by a reduction of monocytes 24 h later. The percentage increase of CD4+ cells 1 h after the exercise could be explained by an increase of the CD4+ Leu 8+ subpopulation.