IL10 and rheumatoid arthritis: However, the concept needs to be tested in human RA, as the role of IL-10 in RA patients is far from clarified: RA patients have significantly elevated levels of IL-10 in synovial fluid [32] while the expression of IL-10 receptors are reduced in synovial tissue [33] compared with osteoarthritic controls, and treatment with systemic recombinant IL-10 in human RA patients has so far not shown any convincing results [34].