TNF and rheumatoid arthritis: In addition, many synovial macrophages (SMs) are present in the RA synovial membrane; these cells not only are dominated by the M1 phenotype, but can also interact with FLS, monocytes, and osteoclasts to increase the secretion of proinflammatory cytokines, including tumor necrosis factor (TNF)‐α, interleukin (IL)‐1β, and IL‐6 [5].