Rheumatoid arthritis (RA) is the most common form of inflammatory rheumatism involving small joints which are the seat for swelling and pain with structural damage, responsible for functional disabilities if no treatment is proposed. The inventors show that circulating MAIT cells were reduced and exhibited an activated and anti-apoptotic phenotype in RA patients compared to healthy controls. MAIT cell levels were also found to be increased in the synovial fluid as compared with the peripheral blood, suggesting that circulating MAIT cell deficiency is due to the migration of MAIT cells into the joint. Severity of arthritis induced by mBSA was reduced in mice depleted in MAIT cells. This data suggest that MAIT cells contribute to exacerbation of arthritis. Thus the present invention relates to the use of an agent capable of inhibiting the activation of MAIT cells for the treatment of rheumatoid arthritis.