IL6 and rheumatoid arthritis: To assess the contribution of cytokines in RA synovial fluid, we neutralized several cytokines with a cocktail of blocking Abs against IL-1β, IL-2, IL-4, IL-6, IL-10, IL-12, IL-13, IL-15, IL-17, IL-18, IL-23, TNF, IFNα, IFNβ, and IFNγ.