The role of Th17 cells in tumor immunity

CD4+ T helper (Th) cells play an important role in modulating immune responses. Th17 cells are a newly established Th subpopulation. Th17 cells differentiate in the presence of TGF-β and IL-6 in mice or IL-1β and IL-6 in humans, depending on the transcription factor RORγt. IL-23 stabilizes the Th17 cells phenotype and helps Th17 cells acquire effector functions. Th17 secretes IL-17, IL-21, and IL-22, which play significant role in the immune response against viruses, extracellular bacteria and fungi, as well as in the pathogenesis of inflammatory diseases. The systemic and local activity of IL-17 and Th17 seems to be an important part of development of autoimmune reaction. Th17 cell subpopulation has been described in many types of cancer, including gastric cancer, melanoma, breast cancer, and ovarian cancer, but it remains unclear whether Th17 cells promote or inhibit tumor progression and the mechanism of their involvement in tumor immunity is unknown. eview summarizes the current knowledge on the role of Th17 cells in tumor immunity.