The potential proinflammatory function in joints of IL-22, a cytokine of the IL-10 family, has been suggested by IL-22 mRNA expression by macrophages and fibroblasts, by MCP-1/CCL2 production and fibroblast proliferation of RA patients [44] and by the promotion of osteoclastogenesis in collagen induced arthritis [45]. This evidence concerns the gene IL22 and rheumatoid arthritis.