ARG1 and rheumatoid arthritis: ARG1 [27] which encodes arginase and HP which encodes haptoglobin [28] are involved in a variety of inflammatory diseases.The protein encoded by TNFAIP6 (tumor necrosis factor, alpha-induced protein 6) was found to be increased in the synovial fluid of patients with osteoarthritis and rheumatoid arthritis [29].