IFNG and rheumatoid arthritis: Furthermore, NK cells found in target non‐lymphoid tissues, such as the inflamed joint of RA patients,81, 82 the central nervous system (CNS) of MS patients,83 and the inflamed skin of psoriasis patients,80 were found to produce high levels of pro‐inflammatory cytokines including IFN‐γ and tumor necrosis factor‐α (TNF‐α).