Barrier-promoting and antimicrobial functions of MAIT cells at the intestinal barrier. Intestinal dysbiosis leads to an expansion of ribD-expressing bacteria, particularly M. schaedleri, resulting in the synthesis of MAIT ligands and the activation of MAIT cells in the lamina propria. During colitis, MAIT cells produce barrier-promoting factors such as IL17A, a cytokine that induces the expression of tight junction proteins (claudin 8 and 2) in epithelial cells; amphiregulin, which stimulates epithelial cell proliferation through the epidermal growth factor receptor; and Furin, involved in TGFβ maturation. MAIT cells also provide antimicrobial mediators, such as IL22, which stimulates epithelial production of antimicrobial peptides, and the inflammatory cytokines IL17F, TNFα, granulysine, granzyme B, and IFNγ, which promote the recruitment of innate immune cells and contribute to bacterial lysis. MAIT cells can also express FasL, leading to FasR-mediated apoptosis of infected cells. Created with Biorender.