Purpose
Investigate training status and sex effects on the redistribution of senescent and naïve T-lymphocytes following acute exercise.

Methods
Sixteen (8 male, 8 female) trained (18.3 ± 1.7 yr) soccer players (Tr) and sixteen (8 male, 8 female) untrained (19.3 ± 2.0 yr) controls (UTr) performed a treadmill running test to volitional exhaustion. Blood lymphocytes were isolated before (Pre), immediately post, and 1-h post-exercise for assessment of cell surface expression of CD28 and CD57 on CD4+ and CD8+ T-lymphocyte subsets. Plasma was used to determine cytomegalovirus (CMV) serostatus.

Results
Exercise elicited a redistribution of T-lymphocyte subsets. Senescent CD4+ and CD8+ T-lymphocytes increased by 42.4% and 45.9% respectively, while naïve CD4+ and CD8+ T-lymphocytes decreased by 8.7% and 22.5% respectively in response to exercise. A main effect (P < 0.05) of training status was observed for senescent CD4+, CD8+ and naïve CD8+ T-lymphocytes: UTr had a higher proportion of senescent and a lower proportion of naïve CD8+ T-lymphocytes than Tr. A main effect (P < 0.05) of sex was observed in senescent CD4+, CD8+ and naïve CD4+, CD8+ T-lymphocytes. Males had a higher proportion of senescent and lower proportion of naïve T-lymphocytes than females. A sex-by-training status interaction (P < 0.05) was observed for the senescent and naïve CD4+ T-lymphocytes (but not CD8+) with the highest percentage of senescent and lowest percentage of naïve T-lymphocytes observed in UTr males. CMV exerted a significant main covariate effect (P < 0.05) in the senescent and naïve (P < 0.05) CD8+ T-lymphocytes but not in the senescent and naïve CD4+ T-lymphocytes.

Conclusion
This study highlights important sex and training status differences in the senescent and naïve T-lymphocyte redistribution in response to exercise that warrants further investigation.