IL-18 is known to be a proinflammatory cytokine that induces the production of interferon (IFN)-γ in T cells [13], and promotes osteoclastogenesis by upregulating receptor activator of nuclear factor-kappa B ligand (RANKL) production in T cells in synovitis in rheumatoid arthritis [14]. This evidence concerns the gene TNFSF11 and synovitis.