Activation, Deficiency, and Reduced IFN-γ Production of Mucosal-Associated Invariant T Cells in Patients with Inflammatory Bowel Disease.

Mucosal-associated invariant T (MAIT) cells are innate-like T cells that can activate either in response to T-cell receptor (TCR) engagement or through activating cytokines and play an important role in autoimmune disorders. The study examined the level and function of MAIT cells in patients with inflammatory bowel disease (IBD). Circulating MAIT cell levels were significantly reduced in IBD patients. This MAIT cell deficiency was correlated with IBD disease activity grades, hemoglobin, and CRP. IFN-γ production of circulating MAIT cells in response to both MHC class 1b-like related protein (MR1)-dependent and -independent stimulations was decreased in IBD patients, which was partially associated with reduced activation of nuclear factor of activated T cells 1 (NFAT1) transcription factor, a main regulator of IFN-γ production. Expression levels of CD69, programmed death-1 (PD-1), and annexin V in MAIT cells were elevated in IBD patients. CCL20, CXCL10, CXCL16, and CCL25 were expressed higher in inflamed intestinal tissues than in noninflamed tissues. This study demonstrates that circulating MAIT cells are activated and numerically and functionally deficient in IBD patients. Furthermore, activated MAIT cells have the potential to migrate to inflamed tissues. These findings suggest an important role of MAIT cells in mucosal immunity in IBD.