Interleukin-17 and Type 17 Helper T Cells

Type 17 helper T cells (Th17) — a third class of T cells — and their major cytokine, interleukin-17, are essential for the defense against certain fungi, extracellular bacteria, and Mycobacterium tuberculosis . Defective control of Th17 cells and production of interleukin-17 are prominent in chronic inflammation and several immunoinflammatory disorders. Monoclonal antibodies against cytokines produced by Th17 cells are being investigated in clinical trials. Type 17 helper T cells (Th17) and their major cytokine, interleukin-17, are essential for the defense against certain fungi, extracellular bacteria, and Mycobacterium tuberculosis. Defective control of Th17 cells and production of interleukin-17 are prominent in chronic inflammation and several immunoinflammatory disorders. In 1986, Mosmann and Coffman introduced the concept of distinct types of helper T cells, which was based on the types of cytokines that T cells produce when they are stimulated to differentiate. They named these lymphocytes type 1 helper T cells (Th1 cells) and type 2 helper T cells (Th2 cells). 1 Th1 cells produce large quantities of interferon-γ, induce delayed hypersensitivity reactions, activate macrophages, and are essential for the defense against intracellular pathogens (Figure 1). Th2 cells produce mainly interleukin-4 and are important in inducing IgE production, recruiting eosinophils to sites of inflammation, and helping to clear parasitic infections . . .