TLR4 and rheumatoid arthritis: Responding to RA-related cytokine stimulation such as IL-1β and TNF-α rather than other cytokines (IFN-γ and IL-4) or TLR-activating ligands (TLR2, TLR3, TLR4, and TLR7 ligands), DICER1 gene expression is significantly reduced at both the mRNA and protein levels in synoviocytes (Fig.  S2).