T helper cell 22 (Th22) is a new subset of T cells clearly separate from Th17 and other known T cell subsets with distinct gene expression and function. With the CCR6 + CCR4 + CCR10 + phenotype and aryl hydrocarbon receptor as the key transcription factor, Th22 subsets produce cytokines such as IL-22, whose function depends on the activation of signal transduction and activators of transcription 3. IL-22 was up-regulated in Rheumatoid arthritis, Crohn's disease, Psoriasis, and atopic dermatitis patients whereas it was down-regulated in the serum of patients with sarcoidosis and systemic lupus erythematosus. Furthermore, it has been demonstrated that IL-22 may have promise as a potential therapeutic for chronic inflammatory diseases, and treatment with recombinant cytokine or gene therapy delivery of IL-22 may alleviate tissue destruction during inflammatory responses. In summary, Th22 cell plays an important and complicated role in inflammatory and autoimmune disease.