With the recent definition of the Th17 cell subset, a new paradigm in innate and adaptive immunity has been established. This book describes the function of the Th17 cell subset and its prevalent role in many inflammatory and autoimmune diseases. The mechanism by which this T cell subset is generated and maintained shows specific differences between mice and man which are reviewed. One characteristic of Th17 cells is to secrete specific and unique cytokines such as IL-17A, IL-17F and IL-22; their functions are described in detail. These cytokines have acquired a prevalent role in many pathological conditions in animal models and in humans. Targeting these cytokines as well as the generation of Th17 cells may open new ways to treat many autoimmune diseases. The role of Th17 in infectious conditions is also addressed.

Zusammenfassung
The IL-17 cytokines represent a novel family of cytokines, which defines a new effector T cell, the Th17 cell, and extend the Th1-Th2 paradigm. Th17 cells in part co-express at least IL-17A and IL-17F, IL-21 and IL-22. IL-17 A/F are produced by T cells ( and ), iNKT cells, and possibly neutrophils, dendritic cells and Paneth cells. The regulation of IL-17 family member's expression, and the identification of effector mechanisms are an area of intense current research. Recognized regulators of IL-17A expression include the nuclear receptor ROR t, proinflammatory cyt- ines such as IL-1, IL-6 with TGF- , IL-21, IL-23 IL-25 in the absence of IFN- and IL-4, which are discussed. Recent data suggest that IL-17A may have a dual fu- tion pro-inflammatory and anti-inflammatory- suggesting that IL-17A may also contribute to terminate inflammation. Further, a reciprocal regulation of Th17 and regulatory T cells including the role of retinoic acid and TGF- is discussed. The discovery that patients with rheumatoid arthritis, allergic disorders, psor- sis and inflammatory bowel disease express IL-17A generated interest in the medical community and instigated a flurry of experimental research on the potential role of Th17 in inflammatory diseases. Experimental studies confirmed that IL-17A is induced and is critical for the development of allergic lung inflammation, arthritis, bacterial sepsis, experimental allergic encephalomyelitis and myocarditis, as well as other inflammatory con- tions including organ transplantation. The role of IL-17F and IL-22 is still poorly defined and is only slowly emerging.

Inhalt
Discovery and IL-17 family.- IL-22 and IL-17: Common and different properties.- Other sources of IL-17: Invariant natural killer T cells.- Contributions of IL-22 to Th17 responses: Repairing and protecting peripheral tissues.- Retinoic acid in mucosal immune-regulation.- IL-25, another promoter of allergy.- Experimental models of disease.- Critical role of IL-17 in experimental arthritis.- Dual role of IL-17 in allergic asthma.- Contribution of IL-17 to the pulmonary inflammatory response.- The role of IL-17 in experimental autoimmune myocarditis.- Th17 cells in organ transplantation.- Role of IL-23/IL-17 in infection and tumor control.- Is IL-17 required to control tuberculosis?.- IL-17 and mucosal host defense.- IL-23 orchestrates the switch from tumor immune surveillance to tumor-promoting inflammation.- IL-17 in clinical autoimmune disease.- IL-17 and Th17 cells in rheumatoid arthritis.- Targeting Th17 cells in CNS immune pathology.- IL-17 cytokines in asthma.- IL-17/23, potential targets for Crohn's disease.- Novel tools and therapeutic avenues.- IL-17A and Th17 cells as therapeutic targets for autoimmune diseases.