TNF and rheumatoid arthritis: In rheumatoid arthritis (RA), for example, the joints are rich in cytokine-secreting cells containing a wide range of effector molecules including pro-inflammatory cytokines such as IL-1β, IL-6, TNF-α and IL-18, chemokines such as IL-8, IP-10, MCP-1, MIP-1 and RANTES, MMPs such as MMP-1, -3, -9 and -13 and metabolic proteins such as Cox-1, Cox-2 and iNOS, which interact with one another in a complex manner suggested to lead to a vicious cycle of high pro-inflammatory signals and chronic and persistent inflammation [140,141].