T-helper 22 cells as a new player in chronic inflammatory skin disorders

T-helper 22 (Th22) cell is a new subset of CD4(+) T cells that secrets interleukin (IL)-22 but not IL-17 or interferon-. Th22 is distinct from Th17 and other known CD4(+) T-cell subsets with distinguished gene expression and function. Th22 subsets have chemokine receptors CCR6(+) CCR4(+) CCR10(+) phenotype and aryl hydrocarbon receptor as the key transcription factor. This T-helper subset, by producing cytokines such as IL-22, IL-13, and tumor necrosis factor-, is implicated in the pathogenesis of inflammatory skin disorder. This review discusses the role of Th22 and its cytokine IL-22 in the immunopathogenesis of inflammatory skin disorders such as psoriasis and atopic dermatitis.