IL6 and rheumatoid arthritis: The exposure of fibroblasts to IL-1β and TNF not only promotes their proliferation but also stimulates their production of RA-exacerbating factors such as IL-6, IL-8, matrix-metalloproteases (MMPs) and reactive oxygen species [268,269,270], as well as chemokines (CCL2, CCL5, CCL8, CXCL5, CXCL10) that increase immune infiltration and activation (reviewed in detail in [265,271,272]).