Th17 cells are subclasses of T helper (Th) CD4+ cells, characterized by the production of interleukin-17 (IL-17), responsible for cell-mediated immunity, induction of inflammation and involvement of neutrophiles; however, in the case of autoimmune disorders, Th17 are the dominant class of cells promoting a pathogenic immune response. The gene discussed is IL17A; the disease is Autoimmunity.