Table 1

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

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Presentation of antigens relevant to disease initiation or severity [93] (Stuhlmuller B, et al., unpublished data) (reviewed in [2])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]


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].

Kinne et al. Arthritis Research & Therapy 2007 9:224   doi:10.1186/ar2333