The Roles of T Helper 1, T Helper 17 and Regulatory T Cells in the Pathogenesis of Sarcoidosis

Sarcoidosis is a systemic granulomatous disorder of unidentified etiology, with a heterogeneous clinical presentation. It is characterized by a reduced delayed-type hypersensitivity to tuberculin and common antigens. The balance between Th1, Th17 and Regulatory T(Treg) cells controls T-cell proliferation and activation. The Th17/Treg ratio in the peripheral blood and bronchoalveolar lavage fluidis increased in patients with active sarcoidosis. Amplified IL-17A expression in granulomas and the presence of IL-17A(+), IL-17A(+) IL-4(+) and IL-17A(+)IFN-gamma(+) memory T helper cells in the circulation and BAL indicate Th17 cell involvement in granuloma induction and/or maintenance in sarcoidosis. Sarcoidosis should therefore be considered as a Th1/Th17 multisystem disorder and anti-IL-17/Th17 approaches that control and reduce IL-17Amay be an option, therefore, for the treatment of sarcoidosis. Here we provide a short overview as to the role of Th17 cells as critical cells in the pathogenesis of sarcoidosis.