However, it has been demonstrated that a number of effector cells (e.g., macrophages, T lymphocytes, and dendritic cells), inflammatory cytokines, such as tumor necrosis factor α (TNF-α), interleukin 1 (IL-1), and interleukin 6 (IL-6), and their interactions contribute to the pathological process of RA (Figure 1) (Smolen et al., 2007; Aletaha and Smolen, 2018). Here, TNF is linked to rheumatoid arthritis.