An ultra-endurance event leads to changes in circulating regulatory T-cells, CD4+ naïve and CD8+ effector memory T-cells in the 48 h post-race recovery period

Purpose
Exercise is known to acutely affect T-lymphocyte populations in the peripheral blood, which is intensity- and duration-dependent. However, effects of longer duration endurance exercise (>5 h) on T-cells in the days following are unknown. The aim of this study was to investigate the circulating T-cell changes that occur in response to an ultra-endurance event, which may provide insight into the inflammatory response to ultra-endurance exercise.

Methods
Ten individuals (m = 7, f = 3) completing an Ironman 70.3 event volunteered for the study. Peripheral blood samples were taken 1–2 days pre-race (PRE-RACE), and 1 day (RACE + 1) and 2 days (RACE + 2) post-race, with circulating T-cells enumerated by flow cytometry (total CD3+, CD4+ and CD8+ T-cells, regulatory T-cells [CD4+CD25+CD127−; TREG], naïve [CD27+CD45RA+; NA], central memory [CD27+CD45RA−; CM], effector memory [CD27−CD45RA−; EM], and effector memory CD45RA+ [CD27−CD45RA+; EMRA]).

Results
There were no changes in total CD3+, CD4+ and CD8+ T-cells. TREG RACE + 1 was significantly higher compared to PRE-RACE, as were the proportion of CD4+ NA cells and CD8+ CM cells at RACE + 2; CD8+ EM cells fell at RACE + 2 (absolute counts and proportion).

Conclusion
In conclusion, the ultra-endurance event evoked T-cell changes over the 48 h recovery period, with an increase in T-cells that regulate the immune response, and a reduction in circulating EM T-cells, most likely trafficked to sites of tissue damage and inflammation.