Figure 1 .

TNFα activity. Macrophages and monocytes are a major source of TNFα, which in turn acts on these and other cells to stimulate the production of biochemical, enymatic, and cytokine mediators of inflammation. Further cellular activity ensues. Specifically TNFα acts on synoviocytes resulting in pannus formation and together with the activation of osteoclasts this results in articular erosions and reduced bone density.