TNF and rheumatoid arthritis: In our study, in order to explain the role of downstream signalling molecules of various cytokine pathways that regulate iNOS in RA, we first constructed an elaborate signalling network of cytokines such as IL-1β, TNF-α, IL-6, IFN-γ, TGF-β, IL-4 and IL-10 using data on interactions between the signal-transducers reported in the literature.