Objective. We previously demonstrated that CD4؉,CD25؉ regulatory T (Treg) cells are present in increased numbers in the synovial fluid (SF) of rheumatoid arthritis (RA) patients and display enhanced suppressive activity as compared with their peripheral blood (PB) counterparts. Despite the presence of these immunoregulatory cells in RA, chronic inflammation persists. The purpose of the present study was to investigate whether particular proinflammatory mediators that are associated with RA could abrogate CD4؉,CD25؉ Treg-mediated suppression.Methods.

Leukocyte-associated Ig-like receptor (LAIR)-1 is a collagen-receptor that inhibits immune cell function upon collagen binding. Next to LAIR-1, the human genome encodes LAIR-2, a putative soluble homolog. In this study we show, for the first time, that the LAIR-2 gene is broadly transcribed in human PBMC, mirroring the expression profile of LAIR-1. LAIR-2 protein is expressed as a soluble receptor exhibiting high affinity for various collagen molecules to which it binds in a hydroxyproline-dependent manner. In vitro stimulation of PBMC induces secretion of LAIR-2. We detect high amounts of LAIR-2 in urine of pregnant women, indicating that the soluble receptor is indeed produced in vivo and can be cleared from the body via urine. Furthermore, LAIR-2 levels are increased in synovial fluid of patients with rheumatoid arthritis as compared with osteoarthritis patients. We hypothesize that soluble LAIR-2 may function as a natural competitor for LAIR-1, thereby regulating its inhibitory potential. Indeed, LAIR-2 prevents binding of human LAIR-1 to collagens and LAIR-1 cross-linking in vitro, suggesting that the protein has an immunoregulatory function in vivo. Hence, we reveal a novel mechanism of immune regulation by a soluble LAIR receptor regulating the inhibitory potential of the membrane-bound LAIR-1 via competition for ligands.

ObjectivesTo evaluate the performance of individual biomarkers and a multi-biomarker disease activity (MBDA) score in the early rheumatoid arthritis (RA) patient population from the computer assisted management in early rheumatoid arthritis (CAMERA) study.MethodsTwenty biomarkers were measured in the CAMERA cohort, in which patients were treated with either intensive or conventional methotrexate-based treatment strategies. The MBDA score was calculated using the concentrations of 12 biomarkers (SAA, IL-6, TNF-RI, VEGF-A, MMP-1, YKL-40, MMP-3, EGF, VCAM-1, leptin, resistin and CRP) according to a previously trained algorithm. The performance of the scores was evaluated relative to clinical disease activity assessments. Change in MBDA score over time was assessed by paired Wilcoxon rank sum test. Logistic regression was used to evaluate the ability of disease activity measures to predict radiographic progression.ResultsThe MBDA score had a significant correlation with the disease activity score based on 28 joints-C reactive protein (DAS28-CRP) (r=0.72; p<0.001) and an area under the receiver operating characteristic curve for distinguishing remission/low from moderate/high disease activity of 0.86 (p<0.001) using a DAS28-CRP cut-off of 2.7. In multivariate analysis the MBDA score, but not CRP, was an independent predictor of disease activity measures. Additionally, mean (SD) MBDA score decreased from 53 (18) at baseline to 39 (16) at 6 months in response to study therapy (p<0.0001). Neither MBDA score nor clinical variables were predictive of radiographic progression.ConclusionsThis multi-biomarker test performed well in the assessment of disease activity in RA patients in the CAMERA study. Upon further validation, this test could be used to complement currently available disease activity measures and improve patient care and outcomes.

Background: A large number of activated T cells are found in the joints of patients with rheumatoid arthritis (RA). Interleukin 7 (IL7), a T cell growth factor and a regulator of Th1 and Th2 cytokine production, is produced by synoviocytes from patients with RA. Objective: To investigate the effect on proinflammatory cytokine production of synovial fluid mononuclear cells (SFMC) and the mechanism by which IL7 influences CD4+ T cell activity in patients with RA. Methods: In a cross sectional group of patients with RA, IL7 levels were compared with those of healthy controls and related to disease activity. The effect of IL7 on cytokine production was tested by RA SFMC and on SF CD4+ T cells in the presence of mononuclear cells (MC). Production of tumour necrosis factor α (TNFα), IL1β, interferon γ (IFNγ), and IL4 was measured by enzyme linked immunosorbent assay (ELISA) and by single cell FACS analysis. Expression of the IL7 receptor α chain on CD4+ T cells (essential for IL7 signalling) was assessed. Direct effects of IL7 on isolated synovial fluid (SF) CD4+ T cells were studied by cytokine analysis. By neutralisation of IL12 in MC cultures, indirect effects of IL7 on T cells through accessory cells were studied. Results: IL7 serum levels were higher in patients with RA than in healthy controls and correlated positively with C reactive protein levels. IL7 stimulated TNFα production by SFMC and very potently stimulated IFNγ and TNFα production by SF CD4+ T cells. These effects were probably mediated through the IL7 receptor α chain, which was abundantly expressed on SF CD4+ T cells. Besides the direct stimulation of T cell cytokine production by IL7, its action was partly dependent on IL12, indicating that IL7 also stimulates accessory cell function, leading to T cell activation. Conclusion: IL7 stimulates proinflammatory cytokine production of intra-articular CD4+ T cells and accessory cells from patients with RA. The correlation with measures of disease activity indicates that IL7 might substantially contribute to the perpetuation of Th1 and TNFα mediated proinflammatory responses in patients with RA.

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Objective. Inflammation‐induced articular cartilage degradation is a major problem in rheumatoid arthritis (RA). Type 1 T cell activity (characterized by interferon‐γ/interleukin‐2 [IL‐2] production), and consequently, the production of the proinflammatory cytokines IL‐1 and tumor necrosis factor α (TNFα), have been reported to play a major role in cartilage damage. IL‐10 and IL‐4, both produced by type 2 T cells, are cytokines with the capacity to down‐regulate proinflammatory responses. The present study was undertaken to investigate the way in which these cytokines affect activated mononuclear cells (MNC) of RA patients in relation to human articular cartilage degradation in vitro. Methods. MNC from synovial fluid and peripheral blood of RA patients were stimulated with bacterial antigen and treated with IL‐10 and/or IL‐4. Bacterial antigen is known to activate type 1 T cells and to induce proinflammatory IL‐1/TNFα–dependent cartilage damage. Cytokine production and effects of conditioned media, as well as effects of IL‐10 and IL‐4 on proteoglycan (PG) turnover (as a measure for cartilage damage), were determined. Results. IL‐10 and IL‐4 inhibited proinflammatory cytokine production of stimulated RA MNC and completely reversed inhibition of cartilage PG synthesis induced by these stimulated RA MNC. IL‐10 was more potent than IL‐4 in this respect, and the combination of IL‐10 and IL‐4 had an additive effect. In addition, IL‐10 directly stimulated cartilage PG synthesis. Conclusion. IL‐10 reverses the cartilage degradation induced by antigen‐stimulated MNC, and IL‐4 has an additive effect on this process. Furthermore, IL‐10 has a direct stimulatory effect on PG synthesis, and IL‐4, as a growth factor for type 2 T cells, can reduce the ratio of type 1 to type 2 T cell activity. These results provide evidence in favor of the use of a combination of the two cytokines in the treatment of RA.

Objective. To study the effects of interleukin-7 receptor ␣-chain (IL-7R␣) blockade on collageninduced arthritis (CIA) and to investigate the effects on T cell numbers, T cell activity, and levels of proinflammatory mediators.Methods. We studied the effect of anti-IL-7R␣ antibody treatment on inflammation and joint destruction in CIA in mice. Numbers of thymocytes, splenocytes, T cell subsets, B cells, macrophages, and dendritic cells were assessed. Cytokines indicative of Th1, Th2, and Th17 activity and several proinflammatory mediators were assessed by multianalyte profiling in paw lysates. In addition, T cell-associated cytokines were measured in supernatants of lymph node cell cultures.Results. Anti-IL-7R␣ treatment significantly reduced clinical arthritis severity in association with reduced radiographic joint damage. Both thymic and splenic cellularity were reduced after treatment with anti-IL-7R␣. IL-7R␣ blockade specifically reduced the total number of cells as well as numbers of naive, memory, CD4؉, and CD8؉ T cells from the spleen and significantly reduced T cell-associated cytokines (interferon-␥, IL-5, and IL-17). IL-7R␣ blockade also decreased local levels of proinflammatory cytokines and factors associated with tissue destruction, including tumor necrosis factor ␣, IL-1␤, IL-6, matrix metalloproteinase 9, and RANKL. IL-7R␣ blockade did not significantly affect B cells, macrophages, and dendritic cells. B cell activity, indicated by serum anticollagen IgG antibodies, was not significantly altered.Conclusion. Blockade of IL-7R␣ potently inhibited joint inflammation and destruction in association with specific reductions of T cell numbers, T cellassociated cytokines, and numerous mediators that induce inflammation and tissue destruction. This study demonstrates an important role of IL-7R-driven immunity in experimental arthritis and indicates the therapeutic potential of IL-7R␣ blockade in human arthritic conditions.