The focus of this study was to assess exercise-induced alterations in circulating γδ T cell subpopulations and memory phenotypes after a prolonged heavy-intensity exercise bout. Ten highly-trained endurance cyclists (mean ± SEM: age 24.0 ± 1.3 years; height 1.81 ± 0.02 m; body mass 73.3 ± 1.8 kg; peak oxygen uptake 60.7 ± 1.5 mL.kg-1.min-1) performed 2 h of cycling exercise at 90% of the second ventilatory threshold. Blood samples were collected before exercise, immediately post-exercise, 1 h, 2 h, 4 h, and 6 h post-exercise. Flow cytometry was used to examine γδ T cell subsets, memory phenotypes and receptor expression. A significant decrease in cell concentration was observed in total γδ T cells and the δ2 subset from pre-exercise to 1 h, 2 h, and 4 h post-exercise. Further analysis of the δ2 subset revealed a significant decrease from pre-exercise to 1 h, 2 h, and 4 h post-exercise in naive δ2 cells, and a significant decrease from pre-exercise to 1 h and 2 h post-exercise in central memory δ2 cells. A significant decrease was observed in γδ T cells expressing CD11ahigh, CD62Lhigh and CD94+ from pre-exercise to 1 h, 2 h, and 4 h post-exercise. Furthermore, a significant decrease was observed from pre-exercise to 1 h post-exercise in CD62Llow and CD94- γδ T cells. These results suggest an exercise-stress-induced redistribution of γδ T cells from the circulation with greater propensity for antigen stimulation, tissue and lymph node homing potential for a duration of 4 h after the cessation of exercise
