IL17A and rheumatoid arthritis: However, less is known about the contribution of specific innate cell populations to perpetuate chronic inflammation and the induction of pathogenic CD4+ T cells able to produce both IL-17 and IFN-γ (known as Th1/Th17 cells), a T cell subset that is enriched in synovial fluid (SF) of patients with RA (7) and has been linked to severity of multiple autoimmune disorders (8–10).