CXCL8 and rheumatoid arthritis: Similarly, protein levels of TNF-α, IL-1β, IL-6, IL-8, MMP-1, MMP-3, and RANKL in the cell culture supernatants of sh-CYLD-transfected RA-FLSs were markedly higher than those in supernatants of sh-GFP-transfected RA-FLSs (Fig. 4b).