T cell responses to exercise stress do not adequately model those from tactical stress events

Abstract

Abstract Military training environments are rigorous, requiring service members to endure not only physical and psychological stress but also sleep deprivation, caloric restriction, and severe thermic challenges. The convention has been to use immunoendocrine responses induced by various exercise regimens to generalize results to the layered stress environments of wartime. The purpose of this study was to determine whether exercise models are accurate representations of the physiologic response to the stress experienced in an operational environment. To achieve this aim we identified changes in T cell proliferative capacity (costimulation through CD3+CD28 or stimulation with PHA) and relevant immunoendocrine interactions following an environment comparable to that experienced in Basic Combat Training. An increased proliferation response was observed post-exercise in T cells isolated from whole blood in the layered stress group with those increases still significant at 6 h post-exercise. In contrast, the moderate exercise group saw no significant changes in proliferative ability immediately after exercise exhibiting what could be expressed as a characteristic exercise response. Analyses of serum stress hormones, immunomodulatory cytokines, and immunoglobulins -G, -M, and -A failed to reveal any correlated variations that could clarify the T cell findings. These data suggest that exposure to a high stress environment leads to increased T cell proliferation that appears to be independent of changes in stress hormone concentrations and immunomodulatory cytokines. We submit that variations in exercise intensity and duration do not necessarily approximate military operational or tactical stress responses.