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Table 1 Activation status of synovial macrophages and/or circulating monocytes in rheumatoid arthritis

From: Cells of the synovium in rheumatoid arthritis. Macrophages

Class of overexpressed molecules Molecules Known or potential function
Class II major histocompatibility complex (overexpressed on Mφ) HLA-DR Presentation of antigens relevant to disease initiation or severity [93] (Stuhlmuller B, et al., unpublished data) (reviewed in [2])
Cytokines and growth factors For example, TNF-α, IL-1, IL-6, IL-10, IL-13, IL-15, IL-18, migration inhibitory factor, granulocyte macrophage colony-stimulating factor, and thrombospondin-1 Mediation and regulation of local and systemic inflammation and tissue remodelling (reviewed in [2,24,39,52])
Chemokines and chemoattractants For example, IL-8, macrophage inflammatory protein-1, monocyte chemoattractant protein-1, and CXCL13 Mediation and regulation of monocyte migration Stimulation of angiogenesis (reviewed in [69])
Metalloproteases (MMPs) MMP-9 and MMP-12 Tissue degradation and post-injury tissue remodelling [94,95]
Tissue inhibitors of MMP (TIMPs) TIMP-1 Attempt to control excessive tissue destruction [96]
Acute-phase reactants For example, C-reactive protein and A-SAA (serum amyloid A) Integrated hormone-like activation of hepatocytes by synovial Mφ and fibroblasts (mostly via IL-6) [97] (reviewed in [2])
Other molecules Neopterin Produced by interferon-gamma-stimulated monocytes/Mφ
Induces/enhances cytotoxicity and apoptosis Acts as antioxidant [98,99]
  Cryopyrin Produced by TNF-α-stimulated Mφ
Regulates nuclear factor-kappa-B and caspase-1 activation [100]
  1. IL, interleukin; Mφ, macrophages; TNF-α, tumor necrosis factor-alpha. Reproduced with permission from Kinne RW, Stuhlmuller B, Palombo-Kinne E, Burmester GR: The role of macrophages in rheumatoid arthritis. In Rheumatoid Arthritis. Edited by Firestein GS, Panayi GS, Wollheim FA. New York: Oxford University Press; 2006:55–75 [2].