[Interleukin-17 in chronic inflammatory and autoimmune diseases: rheumatoid arthritis, Crohn's disease and Wegener's granulomatosis].

Data from recent animal experiments and clinical studies show that interleukin-17 (IL-17A, B, C, D, E, and F) plays an important role as proinflammatory cytokine in the host response to extracellular bacteria and in chronic inflammatory and autoimmune diseases. These findings have led to a revision of the well-known T(H)1/T(H)2 hypothesis. In rheumatoid arthritis elevated IL-17 serum levels, Th-17 cells in synovial fluid and in T-cell-rich areas of inflamed synovia are found. In Wegener's granulomatosis, IL-17D is expressed in nasal granulomas. In Crohn's disease IL-17 as well as IL-17 plus IFN-gamma producing CD4(+) T-cells are detected in peripheral blood and inflamed intestinal mucosa. So far, CD4(+)IL-17(+)IFN-gamma(+) T-cells have been described only in humans. These and other findings indicate a number of differences in the cytokine response between murine models and human beings.