In RA, FLS proliferation releases several anti-inflammatory cytokines and growth factors, among which are tumor necrosis factor (TNF), interleukin (IL) (such as IL-6, IL-1β, and IL-17), chemokines, and inflammatory enzymes [such as nitric oxide synthase (NOS) and cyclooxygenase-2 (COX-2)]. Here, IL17A is linked to rheumatoid arthritis.