IL22 and rheumatoid arthritis: Here, we review the characteristics and effector mechanisms of Th22 cells, with an emphasis on the role of Th22 cells and their main effector cytokine IL-22 in the pathogenesis of autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriasis,multiple sclerosis (MS), immune thrombocytopenia (ITP), immunoglobulin A nephropathy (IgAN), autoimmune hepatitis (AIH), autoimmune thyroid diseases (AITD), myasthenia gravis (MG), and systemic sclerosis (SSc).