TNF and rheumatoid arthritis: In another study, Richardson et al. [25] compared levels of Interleukin-8 (IL-8), IL-1β, Interleukin-6 (IL-6), Interleukin-10 (IL-10), TNF, and Interleukin-12 (IL-12) in synovial fluid samples from OA, RA, and normal patients.