The knowledge of Th17 cells and other cell populations which secrete IL-17A, and/or IL-22 has expanded tremendously since the publication of the first edition "Th17 Cells: Role in Inflammation and Autoimmune Disease" in 2008. The present volume has been completely revised with the addition of new chapters on the IL-17 receptor family and signaling, and an in-depth review of IL-22 and innate lymphoid cells. The differentiation of naïve T cells into regulatory T cells and Th17 cells as well as the plasticity of Th17 cells is discussed. The role of IL-22 in cutaneous inflammation including psoriasis has been reviewed. In addition, the volume contains critical updates on autoimmunity, organ transplantation, tumor immunology and genetic mouse models for mechanistic studies. Lastly, the latest clinical progress in neutralizing antibodies to IL-17A, IL-17RA not only confirms the therapeutic promise foreseen in 2008, but also improves our knowledge of the pathogenesis of autoimmune diseases. In summary, this is a timely update and important review of the clinical and experimental aspects of IL-17, IL-22 and their producing cells.