The impact of 6-month training preparation for an Ironman triathlon on the proportions of naïve, memory and senescent T cells in resting blood

Abstract

Athletes appear to be at a greater risk of illness while undertaking arduous training regimens in preparation for endurance events. As infection susceptibility has been linked with increased proportions of differentiated and senescent T cells in the periphery, changes in the proportions of these cell types due to long-term high-volume exercise training could have important implications for athlete infection risk. This study examined the effects of 6-month training preparation for an Ironman triathlon on the proportions of naïve, memory and senescent T cells in resting blood. Ten club-level triathletes (9 males; 1 female: 43 ± 3 years) were sampled at 27 (December), 21 (January), 15 (March), 9 (May) and 3 (June) weeks before an Ironman Triathlon. An additional sample was collected 2-week post-competition (August). Four-colour flow cytometry was used for the phenotypic analysis of CD4+ and CD8+ blood T cells. Proportions of differentiated (KLRG1+/CD57-) CD8+ T cells and "transitional" (CD45RA+/CD45RO+) CD4+ and CD8+ T cells increased with training, as the values in June were elevated 37, 142 and 116%, respectively, from those observed in December. Proportions of senescent (KLRG1+/CD57+) CD4+ or CD8+ T cells did not change during the training phase. Two weeks post-race, proportions of differentiated CD8+ T cells had returned to baseline values, while the proportions of senescent CD4+ T cells increased 192% alongside a 31% reduction in naïve (CD45RA+/CD45RO-) cells. In conclusion, increases in differentiated and "transitional" T cells due to arduous exercise training could compromise host protection to novel pathogens and increase athlete infection risk, although whether or not the composition of naïve and differentiated T cells in blood can serve as prognostic biomarkers in athletes remains to be established.

Frequent participation in high volume exercise throughout life is associated with a more differentiated adaptive immune response

“…In contrast, frequent periods of intense/very intense exercise or a high volume of exercise may induce different effects. Accordingly, Cosgrove et al have reported an accumulation of differentiated T-cells in response to a 6-month training regimen in a group of club level triathletes (Cosgrove et al, 2012). In our groups of athletes, who reported frequent participation in high volume exercise throughout life, we also found a more differentiated phenotype and reduced functional abilities in T-cell subsets.…”

Lifelong training improves anti-inflammatory environment and maintains the number of regulatory T cells in masters athletes

“…The immunological mechanisms that underlie this apparent increase in infection susceptibility in athletes are probably multi-factorial and include perturbations of the T-cell compartment (Cosgrove et al 2012;Tossige-Gomes et al 2014;Simpson et al 2015).…”

Preferential Mobilization and Egress of Type 1 and Type 3 Innate Lymphocytes in Response to Exercise and Hypoxia

“…Where previous studies have provided a fixed concentration of oxygen in inspired air, this study provided a variable concentration of oxygen in the air with the goal of maintaining a consistent systemic hypoxia dose across HYPEX and HYPREST (i.e., 86% SpO2 [5,6]. The acute exposure to hypoxia in the present study is unlikely to induce the same physiological changes as living or training at altitude, but nevertheless it does represent a significant acute stress on the immune system.…”

“…In contrast, CD8 + T cells are required to kill virus infected cells. Several groups have identified preferential mobilisation of memory T cells into the blood in response to acute exercise, with a corresponding reduction in naive T cells [3][4][5][6][7]. However, these changes tend to be transient and cell populations return to baseline levels within a few hours after the cessation of exercise.…”