Changes in naïve and memory T-cells in elite swimmers during a winter training season

High intensity training regimens appear to put athletes at a higher risk of illness. As these have been linked to alterations in the proportions of differentiated T cells, how training load affects these populations could have important implications for athlete susceptibility to disease. This study examined the effect of a winter training season on the proportions of circulating naïve and memory T cells subsets of high competitive level swimmers. Blood samples were taken at rest at 4 time-points during the season: before the start of the season (t0-September), after 7 weeks of an initial period of gradually increasing training load (t1-November), after 6 weeks of an intense training cycle (t2-February) and 48 h after the main competition (t3-April) and from eleven non-athlete controls at 2 similar time-points (t2 and t3). CD4, CD8 and gamma-delta (γδ) T cells expressing the naïve (CCR7CD45RA), central-memory (CM-CCR7CD45RA), effector-memory (EM-CCR7CD45RA) and terminal effector (TEMRA-CCR7CD45RA) were quantified by flow cytometry. Statistical analyses were performed using multilevel modeling regression. Both T CD4 naïve and CM presented a linear increase in response to the first moment of training exposure, and had an exponential decrease until the end of the training exposure. As for TCD4 EM, changes were observed from t2 until the end of the training season with an exponential trend, while TCD4 TEMRA increased linearly throughout the season. TCD8 naïve increased at t1 and decreased exponentially thereafter. TCD8 TEMRA values decreased at t1 and increased exponentially until t3. γδT-EM had an increase at t1 and an exponential decrease afterwards. In contrast, γδT-TEMRA decreased at t1 and exponentially increased during the remaining 20 weeks of training. An increase in TEMRA and EM T cells alongside a decrease in naïve T cells could leave athletes more susceptible to illness in response to variation in training stimulus during the season. © 2014 Elsevier Inc. All rights reserved.