A link between exercise, immunity and gastrointestinal health has yet to be established, however the discovery of MR1 restricted lamina propria V alpha 7.2+ T cells (MAIT cells) has provided an opportunity to explore this phenomena since these cells can be detected in blood where they constitute up to 10% of the peripheral T lymphocyte pool. Furthermore, studies have shown that ablation of MAIT cells can lead to inflammatory responses reminiscent of inflammatory bowel disease (IBD). Since it is unknown as to whether exercise can influence MAIT cells (and gastrointestinal immunity) we set to address this phenomenon in an acute exercise model. Healthy men performed a graded exercise test to exhaustion on a cycle ergometer. Fasted blood samples were obtained before and immediately after exercise. Peripheral blood mononuclear cells (PBMCs) were isolated using density gradient centrifugation and were labelled to identify specific immune cell populations using flow cytometry. Whole blood analysis revealed that total leukocyte count increased by 90%, along with increases in lymphocyte (+128%) and neutrophil counts (+58%; all P<0.001). In PBMCs, there was an increase in absolute leukocyte counts (+ 65%, P=0.001) but the 38% increase in MAIT cells did not reach significance. However, the percentage of MAITs post exercise was greater than baseline (+∆4%, P=0.018). When normalised to PBMC counts, the number of MAITs and their subpopulations (CD8+ and CD4-CD8-) were elevated after exercise (+116-174%, P<0.05). Lymphocyte expansion immediately post exercise was accompanied by increases in functional MAIT cells and is consistent with previous reports on classical T cells. As MAITs comprise a significant proportion of T cells and are particularly abundant in mucosal sites, increases in circulating MAIT cell numbers may lead to improved mucosal immunity which may have implications on the potential health of patients with IBD or other gastrointestinal disorders.