IL17A and rheumatoid arthritis: These cells accumulate in the synovial fluid of patients with RA and promote osteoclastogenesis in the first place by the secretion of IL-17 that stimulates RANKL expression by syno-vial fibroblasts (Hirota et al., 2007[59]; Kontake et al., 1999[71]; Nistala et al., 2008[86]; Sato et al., 2006[110]).