TLR4 and rheumatoid arthritis: This conclusion is supported by the following observations: (1) IL-29 induces IL-6 and IL-8 mRNA and protein expression in RA-FLS; (2) IL-29 increases mRNA and protein expression of TLR2, TLR3 and TLR4 in RA-FLS; and (3) TLR2, TLR3 and TLR4 ligands elevate the expression of IL-6 and IL-8 in RA-FLS.