While Th1 cells activate macrophages to serve as APCs and are the source of various proinflammatory cytokines, such as IFN-γ, IL-2 and TNF-α [136,137], Th17 cells not only stimulate the production of proinflammatory cytokines, chemokines and matrix metalloproteinases (MMPs) in RA synovial fibroblasts but also promote pannus growth, osteoclastogenesis and synovial angiogenesis via IL-17 production [138]. This evidence concerns the gene TNF and rheumatoid arthritis.