IL6 and rheumatoid arthritis: Cytokines produced by immune cells and inflammatory synovial fibroblasts including Interleukin-17 (IL-17), Interleukin-6 (IL-6), and receptor activator of nuclear factor kappa-Β ligand (RANKL)18 also showed no difference between the two RA groups (Fig. 1c and Supplementary Fig. 1a).