Objective. To evaluate the expression of Toll-like receptors (TLRs) 3 and 7 in synovium and to study potential differences in the maturation and cytokine production mediated by TLR-2, TLR-3, TLR-4, and TLR-7/8 by dendritic cells (DCs) from rheumatoid arthritis (RA) patients and DCs from healthy controls.Methods. Synovial expression of TLR-3 and TLR-7 in RA was studied using immunohistochemistry. Monocyte-derived DCs from RA patients and healthy controls were cultured for 6 days and subsequently stimulated for 48 hours via TLR-mediated pathways (lipoteichoic acid, Pam 3 Cys, and fibroblast-stimulating lipopeptide 1 for TLR-2, poly[I-C] for TLR-3, lipopolysaccharide and extra domain A for TLR-4, and R848 for TLR-7/8). Phenotypic DC maturation was measured using flow cytometry. The secretion of tumor necrosis factor ␣ (TNF␣), interleukin-6 (IL-6), IL-10, and IL-12 was measured using the Bio-Plex system. Cell lines expressing TLR-2 and TLR-4 were used for the detection of TLR-2 and TLR-4 ligands in serum and synovial fluid from RA patients.Results. TLR-3 and TLR-7 were highly expressed in RA synovium. All TLR ligands elicited phenotypic DC maturation equally between DCs from RA patients and those from healthy controls. TLR-2-and TLR-4-mediated stimulation of DCs from RA patients resulted in markedly higher production of inflammatory mediators (TNF␣ and IL-6) compared with DCs from healthy controls. In contrast, upon stimulation of TLR-3 and TLR-7/8, the level of cytokine production was equal between DCs from RA patients and those from healthy controls. Remarkably, both TLR-3 and TLR-7/8 stimulation resulted in a skewed balance toward IL-12. Intriguingly, the combined stimulation of TLR-4 and TLR-3-7/8 resulted in a marked synergy with respect to the production of inflammatory mediators. As a proof of concept, TLR-4 ligands were increased in the serum and synovial fluid of RA patients.Conclusion. TLRs are involved in the regulation of DC activation and cytokine production. We hypothesize that various TLR ligands in the joint trigger multiple TLRs simultaneously, favoring the breakthrough of tolerance in RA.

Objective. Directional migration of leukocytes is orchestrated by the regulated expression of chemokine receptors and their ligands. The receptor CXCR6 is abundantly expressed by Th1-polarized effector/ memory lymphocytes accumulating at inflammatory sites. This study was undertaken to examine the presence of CXCR6؉ T cells and of CXCL16, the only ligand for CXCR6, in the joints of patients with rheumatoid arthritis (RA).Methods. Flow cytometry analysis of the expression of CXCR6 by peripheral blood and synovial fluid (SF) T cells. In addition, by performing conventional and real-time reverse transcriptase-polymerase chain reaction, immunohistochemistry, and enzyme-linked immunosorbent assay, we determined the expression of CXCL16 and its protease ADAM-10 within synovium and by cultured macrophages. SF T cell migration was studied with the Transwell system.Results. Accumulation of CXCR6؉ T cells within RA SF coincided with highly elevated levels of CXCL16؉ macrophages. In vitro studies revealed that monocytes started to express CXCL16 upon differentiation into macrophages, and that RA SF and tumor necrosis factor (TNF) enhanced CXCL16 expression. Moreover, RA patients responding to anti-TNF therapy showed a strongly decreased CXCL16 expression, whereas nonresponding patients did not. Interestingly, ADAM-10, a recently identified protease of CXCL16, was abundantly expressed by CXCL16؉ macrophages in vitro and in RA in vivo, which resulted in increased levels of cleaved CXCL16 in RA SF relative to controls. Finally, CXCR6؉ T cells from RA SF were attracted by CXCL16.Conclusion. These data provide evidence that enhanced production of CXCL16 in RA synovia leads to recruitment of CXCR6؉ memory T cells, thereby contributing to the inflammatory cascade associated with RA pathology.

Background: Dendritic cells orchestrate pivotal immunological processes mediated by the production of cytokines and chemokines. Objective: To assess whether neutralisation of tumour necrosis factor a (TNFa) during maturation of dendritic cells affects their phenotype and behaviour, which might explain the beneficial effects of TNFa neutralisation in rheumatoid arthritis. Methods: Immature and fully matured dendritic cells were cultured from blood monocytes from patients with rheumatoid arthritis and healthy controls following standardised protocols. TNFa was neutralised by addition of the p55 soluble TNFa receptor, PEGsTNFRI. The effect of TNFa neutralisation on the phenotype (CD14, CD16, CD32, CD64, CD80, CD83, CD86, and MHC) of dendritic cells was investigated by flow cytometry. Expression of chemokines (CCL17, CCL18, CCL19, CCL22, CCL3, and CXCL8) and production of IL1b and IL6 during dendritic cell differentiation and maturation were examined. Results: Neutralisation of TNFa during the differentiation and maturation of dendritic cells did not result in an altered dendritic cell phenotype in the rheumatoid patients or the healthy controls. In contrast, the expression of CCL17, CCL18, CCL19, CCL22, CCL3, and CXCL8 by dendritic cells was significantly reduced when TNFa activity was inhibited during lipopolysaccharide triggered dendritic cell maturation. The production of IL1b and IL6 by mature dendritic cells was inhibited by PEGsTNFRI. Conclusions: Inhibition of TNFa activity during dendritic cell maturation leads to the development of semimature cells. These data suggest a novel pathway by which the neutralisation of TNFa might exert its therapeutic effects.

No abstract

Our results suggest that elevated CCL18 levels in SSc are not caused by an intrinsically enhanced CCL18 secretion by monocytes/macrophages but are, at least partly, orchestrated by an enhanced IL-10 secretion by TLR4-stimulated DCs. These observations suggest a role for TLR4 ligands and DCs in the pathogenesis of SSc, a topic that warrants further investigation.