IL18 and rheumatoid arthritis: Indeed, MAIT cells accumulate in lesions of patients with multiple sclerosis, rheumatoid arthritis, inflammatory bowel diseases, and mycobacterial infection [5, 12, 22, 28, 30, 34], and the activated status of MAIT cells positively correlated with both the plasma levels of IL-18 and disease activity in ulcerative colitis [28].