TLR2, TLR3, TLR4, and TLR7 were highly expressed on synovial tissue, and synovial tissue macrophages, and the levels of TLR2 and TLR4 expression were associated with IL-12 and IL-18 levels in synovial tissue in RA (56, 57). Here, TLR7 is linked to rheumatoid arthritis.