Expression of Toll-like receptor 2 on CD16+ blood monocytes and synovial tissue macrophages in rheumatoid arthritis

Arthritis Rheum. 2004 May;50(5):1457-67. doi: 10.1002/art.20219.


Objective: CD16 (IgG Fcgamma receptor type IIIA [FcgammaRIIIA])-expressing CD14+ monocytes express high levels of Toll-like receptor 2 (TLR-2) and are able to efficiently produce proinflammatory cytokines such as tumor necrosis factor alpha (TNFalpha). To understand the role of CD16 and TLR-2 in monocyte and macrophage activation in rheumatoid arthritis (RA), we investigated the expression of TLR-2 on CD16+ blood monocytes and synovial tissue macrophages and the effect of CD16 and TLR-2 activation on cytokine production.

Methods: The expression of CD14, CD16, TLR-2, and TLR-4 on blood monocytes was measured by flow cytometric analysis. CD16 and TLR-2 expression in RA synovial tissue was detected by 2-color immunofluorescence labeling. CD16+ mature monocytes were prepared by incubating blood monocytes in plastic plates for 24 hours. These adhered monocytes were stimulated with lipoteichoic acid (LTA), anti-FcgammaRIII antibody, and Hsp60 for 5 hours, and culture supernatants were measured for various cytokines by immunoassay. The activation of NF-kappaB was detected by electrophoretic mobility shift assay.

Results: The frequency of CD16+ cells in all blood monocytes was significantly increased in patients with RA compared with healthy controls. TLR-2 was expressed at higher levels on CD16+ monocytes than on CD16- monocytes, while TLR-4 was expressed similarly on both monocytes. In RA synovial tissue, CD16+/TLR-2+ cells were distributed mainly in the lining layer. TLR-2 expression on monocytes was enhanced by macrophage colony-stimulating factor (M-CSF) and interleukin-10 (IL-10), but was reduced by transforming growth factor beta1, while CD16 expression was inducible by these cytokines. Adhered monocytes ( approximately 50% CD16+) produced TNFalpha, IL-1beta, IL-6, IL-8, IL-12 p40, IL-1 receptor antagonist, and IL-10 after LTA stimulation. This cytokine response was inhibited significantly by anti-TLR-2 antibody and partly by anti-TLR-4 antibody. Anti-FcgammaRIII antibody stimulation markedly enhanced the LTA-induced TNFalpha response. Hsp60 could stimulate TNFalpha production by adhered monocytes, which was inhibited similarly by anti-TLR-2 antibody and anti-TLR-4 antibody. NF-kappaB activation in adhered monocytes was induced by LTA, but this NF-kappaB activity was not augmented by anti-FcgammaRIII antibody stimulation.

Conclusion: These results suggest that CD16+ monocytes and synovial tissue macrophages with high TLR-2 expression may be induced by M-CSF and IL-10, and their production of TNFalpha could be simulated by endogenous TLR ligands such as Hsp60 and FcgammaRIIIA ligation by small immune complexes in RA joints.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antibodies / pharmacology
  • Arthritis, Rheumatoid / immunology*
  • Arthritis, Rheumatoid / metabolism
  • Cells, Cultured
  • Chaperonin 60 / metabolism
  • Cytokines / metabolism
  • Female
  • Flow Cytometry
  • Humans
  • Interleukin-10 / pharmacology
  • Ligands
  • Lipopolysaccharide Receptors / metabolism
  • Lipopolysaccharides / pharmacology
  • Macrophage Colony-Stimulating Factor / pharmacology
  • Macrophages / drug effects
  • Macrophages / immunology
  • Macrophages / metabolism*
  • Male
  • Membrane Glycoproteins / metabolism*
  • Middle Aged
  • Monocytes / drug effects
  • Monocytes / immunology
  • Monocytes / metabolism*
  • NF-kappa B / metabolism
  • Receptors, Cell Surface / metabolism*
  • Receptors, IgG / immunology
  • Receptors, IgG / metabolism
  • Synovial Membrane / cytology*
  • Synovial Membrane / immunology
  • Teichoic Acids / pharmacology
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • Toll-Like Receptors
  • Transforming Growth Factor beta / pharmacology
  • Transforming Growth Factor beta1
  • Tumor Necrosis Factor-alpha / metabolism


  • Antibodies
  • Chaperonin 60
  • Cytokines
  • Ligands
  • Lipopolysaccharide Receptors
  • Lipopolysaccharides
  • Membrane Glycoproteins
  • NF-kappa B
  • Receptors, Cell Surface
  • Receptors, IgG
  • TGFB1 protein, human
  • TLR2 protein, human
  • TLR4 protein, human
  • Teichoic Acids
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • Toll-Like Receptors
  • Transforming Growth Factor beta
  • Transforming Growth Factor beta1
  • Tumor Necrosis Factor-alpha
  • Interleukin-10
  • lipoteichoic acid
  • Macrophage Colony-Stimulating Factor