 Interleukin-17-Illinois-17 is a pro-inflammatory cytokine that is involved in the pathogenesis of several autoimmune diseases. Illinois-17 is produced by T-17 cells, a subset of helper T cells, and by T cells and innate lymphoid cells. Illinois-17 promotes the development and maintenance of pathogenic T-17 cells in autoimmune diseases. This article was authored by Toku Puabara, Fumio Ishikawa, Motonari Kondo, and others.