Exercise Increases Mucosal-associated Invariant T Cell Cytokine Expression but Not Activation or Homing Markers.

Mucosal-associated invariant T (MAIT) cells have properties of both the innate and adaptive immune systems but are an understudied population within exercise immunology. These lymphocytes aggregate at the mucous membranes, but it is unknown if submaximal exercise alters their circulating numbers or function.
PURPOSE: To determine the MAIT cell response to submaximal exercise on activation and homing marker expression and stimulated cytokine production.
METHODS: Twenty healthy, young, recreationally active males cycled for 40 min at 86% of VT after an overnight fast. Peripheral blood mononuclear cells were isolated and labeled to identify specific MAIT cell populations using flow cytometry. Cytokine production after stimulation was also determined.
RESULTS: Mucosal-associated invariant T cells were 2.9% of T cells and increased to 3.9% after exercise and with recovery whereas cell numbers significantly increased by 91.5% after exercise before returning to resting levels. Chemokine and activation marker absolute cell number significantly increased while expression levels remained constant but the high levels of CCR5 may help direct MAIT cells to sites of inflammation. After stimulation, TNFα expression significantly increased after exercise before returning to baseline with a similar trend for IFNγ.
CONCLUSIONS: The MAIT cell numbers undergo a partial biphasic response after submaximal exercise and appear to be preferentially mobilized within T cells; however, the magnitude of the submaximal response was attenuated relative to maximal exercise. Stimulated MAIT cells increase TNFα expression, indicating greater responsiveness to pathogens after acute exercise.