IFNG and rheumatoid arthritis: We examined whether the levels of the sIL-18Rα complex, IgM RF, anti-CCP antibody, IL-18, IL-13 and IFN-γ were increased in the sera of RA patients and compared to the levels in patients with inflammatory joint disease (adult-onset Still's disease), a noninflammatory arthritic condition (OA) and an autoimmune disease (SLE) (Figure 3).