IL6 and rheumatoid arthritis: FLSs have a major effect on RA mediated by their aggressive proliferation and production of proinflammatory cytokines such as interleukin-6 (IL-6) (Nanki et al., 2001; Nagatani et al., 2007; Wei et al., 2012; Stephenson et al., 2018; Yu et al., 2018).