IMMUNOMODULATIONS OF THYMOCYTES AND SPLENOCYTES IN TRAINED RATS

The aim of this study was to describe the effects of training (running) on thymus and spleen cells in the rat. Young Wistar control rats (n = 6), rats trained for 4 wk (n = 5), and rats trained for 4 wk followed by 1 wk of intensive training (3 h/day, n = 6) were studied. Various lymphocyte surface and nuclear markers were determined by immunocytochemistry. The results show that 4 wk of training 1) decreased the percentage of bromodeoxyuridine (BrdU+) thymocytes (cell in phase S of the cycle, immature thymocytes; P < 0.05) and the viability of thymocytes stimulated with concanavalin A (Con A; P < 0.05) and 2) increased the absolute number of CD8+ (suppressor/cytotoxic T cells; 29%) and the percentage of CD8+ splenocytes (P < 0.01). An additional week of intensive training in the 4-wk trained rats induced 1) a decrease in the absolute number of thymocytes (25%, P < 0.05), TCR+ thymocytes, splenocytes (28%, P < 0.01), T, CD4+ (helper T cells; 34%), and CD8+ (31%) splenocytes (P < 0.01) and 2) an increase in the viability of splenocytes after stimulation with Con A for 72 h (P < 0.05). The total effect of 5 wk of training did not significantly affect thymus cells but 1) decreased the absolute number of splenocytes (P < 0.01) and the absolute number and the percentage of CD4+ splenocytes (P < 0.05) and 2) increased the percentage of CD8+ splenocytes (P < 0.05), the percentage of BrdU+ cells (P < 0.05) in culture stimulated with Con A, and the viability of CD4+ splenocytes (P < 0.05). These results suggest that the effect of training modulates both the number and function of the immunocompetent cells of the primary and secondary lymphoid compartments. The mechanisms and the repercussions on the quality of health associated with these chronic exercise-induced immunomodulations remain to be determined.