Roles of T helper 17 cells and interleukin-17 in neuroautoimmune diseases with emphasis on multiple sclerosis and Guillain-Barré syndrome as well as their animal models.

The identification of T helper 17 (Th17) cells challenges the Th1/Th2 paradigm of the immune response and invites intensive exploration of their mechanisms and functions in the field of autoimmune diseases, host defense, allergy, etc. The collective data have shown that transforming growth factor-β (TGF-β), interleukin (IL)-6, IL-1β, IL-21, and IL-23 are involved in the differentiation program of Th17 cells. The transcription factors RORγT, STAT3, RORγ, RORα, and IRF4 exert regulatory effects on the development of Th17 cells. Among the Th17-related effector cytokines, such as IL-17, IL-17F, IL-21, and IL-22, IL-17 is regarded as a key cytokine to induce inflammatory responses. This review outlines the cytokines and transcription factors involved in the differentiation of Th17 cells and their effector functions, with specific focus on the roles of Th17 cells and IL-17 in neuroautoimmune diseases, especially in multiple sclerosis and Guillain-Barré syndrome, as well as in their animal models, experimental autoimmune encephalomyelitis and experimental autoimmune neuritis.