TNF and rheumatoid arthritis: Helen et al. measured 12 cytokine concentrations in the SF of patients with inflammatory arthritis (42 RA patients and 19 non-RA patients) and they reported that the SF from RA patients contained significantly elevated levels of a wide variety of cytokines (e.g., IL-1β, IL-17, IFN-γ and TNF-α) compared with the SF from non-RA patients [44].