Inflammation is progressed by the action of pro-inflammatory cytokines, including IL-1, TNF, IFN-gamma and IL-6, and is resolved by anti-inflammatory cytokines, such as IL-4, IL-10, IL-13, IFN-alpha and transforming growth factor-beta (TGF-beta). Intracellular signal transduction pathways initiated by these cytokines have been studied extensively; these pathways ultimately activate transcription factors, such as NF-kappa B, Smad and STATs. Recently, negative feedback regulation of these pathways, mediated by molecules such as A-20, Smad7 and CIS/SOCS family proteins, has been identified. Negative regulation of cytokine signaling is quite important for inflammation.