Barbara Vitolo

Mature Antigen-Experienced T Helper Cells Synthesize and Secrete the B Cell Chemoattractant CXCL13 in the Inflammatory Environment of the Rheumatoid Joint

OBJECTIVE Synovial B cells play a critical role in rheumatoid arthritis (RA), being involved in autoantibody synthesis, T cell activation, and cytokine production. CXCL13 is a B cell chemoattractant that is instrumental in synovial B cell organization; the regulatory determinants of CXCL13 in inflammation are poorly characterized. This study was undertaken to investigate the functional involvement of synovial T cells in the ectopic expression of CXCL13 in RA. METHODS CXCL13 production and regulation were addressed using immunohistochemistry, in situ hybridization, quantitative polymerase chain reaction, multicolor flow cytometry, and enzyme-linked immunosorbent assay, by in situ-ex vivo analysis and in vitro functional assays with rheumatoid synovial tissue and primary cells. RESULTS CXCL13 messenger RNA and protein expression and spontaneous CXCL13 secretion were detected in RA synovial fluid T cells but were not detected (or were detected only occasionally) in peripheral blood T cells. Analysis of tissue expression confirmed cytoplasm localization of CXCL13 in T lymphocytes infiltrating B cell follicles and small perivascular aggregates. Multicolor characterizations in synovial fluid demonstrated CXCL13 expression in antigen-experienced T helper cells, frequently characterized by terminal differentiation and the lack of the follicular helper T cell markers CXCR5 and BCL6 protein. In vitro functional assays revealed the enhancing effect of T cell receptor-CD28 engagement on CXCL13 production and secretion in primary cells. CONCLUSION Our findings define a new functional property of synovial T cells, demonstrating their active involvement in the local production of B cell chemoattractants, and support a direct contribution of the adaptive immune system and antigen-dependent signals in the mechanisms of B cell localization in RA.

B Cells in Rheumatoid Arthritis: From Pathogenic Players to Disease Biomarkers

The therapeutic benefit of depleting B cells in rheumatoid arthritis (RA) has refocused attention on B cells with increasing awareness on their role in autoimmunity and their function beyond autoantibody production. The rapid increase in our comprehension of B-cell pathobiology is progressively opening novel perspectives in the area of B cell-targeted therapies with the expectation to define more specific approaches able to preserve the homeostasis of the humoral response while disrupting the pathogenic components. In parallel, B-cell activity in RA is starting to be explored in its clinical value, in search of novel biomarkers embedded in the pathogenic process that could help classifying the disease and predicting its heterogeneous outcome beyond inflammation dynamics. In this review, we summarize current knowledge on the multiple roles that B cells play in several aspects of RA. We also analyze their distribution and potential function in different anatomic compartments with specific reference to the main sites in which the disease may be sustained and exert its detrimental effects: the systemic circulation, synovium, bone marrow, and draining lymph nodes. We also highlight novel data encouraging further research in the field of biomarkers related to B cells and their regulatory factors.

Potential involvement of IL-9 and Th9 cells in the pathogenesis of rheumatoid arthritis

OBJECTIVE IL-9 has been shown to be upregulated before the clinical onset of articular disease in RA. The exact role of IL-9 and Th9 cells in RA, however, has not yet been adequately studied. The aim of this study was to evaluate the expression of IL-9 and IL-9-expressing cells in RA patients. METHODS IL-9, IL-9R, PU.1, IL-9, thymic stromal lymphopoietin (TSLP), IL-4 and TGF-β expression was assessed by real-time-PCR in the synovial tissues of RA and OA patients. IL-9, IL-9R, IL-4, TSLP and TGF-β were also investigated by immunohistochemistry. Peripheral CD4(+) T cell subsets were studied by flow cytometry analysis before and after incubation with citrullinated peptides. RESULTS IL-9 was overexpressed in RA synovial tissues and correlated with the degree of histological organization of B and T cells in ectopic lymphoid structures. The majority of IL-9-producing cells were identified as CD3(+) cells. Increased mRNA and protein expression of IL-9R, IL-4, TSLP and TGF-β was also observed in RA synovial tissue. Blood peripheral Th9 cells were expanded by citrullinated peptides. CONCLUSION These results indicate that Th9 cells and IL-9 were frequently detected in peripheral blood mononuclear cells and synovia of RA patients. A possible pathogenic role for Th9 in RA is discussed.

Serum levels of CXCL13 are associated with ultrasonographic synovitis and predict power Doppler persistence in early rheumatoid arthritis treated with non-biological disease-modifying anti-rheumatic drugs.

IntroductionBiological markers specifically reflecting pathological processes may add value in the assessment of inter-individual variations in the course of rheumatoid arthritis (RA). The current study was undertaken to investigate whether baseline serum levels of the chemokine CXCL13 might predict clinical and ultrasonographic (US) outcomes in patients with recent-onset RA.MethodsThe study included 161 early RA patients (disease duration < 12 months) treated according to a disease activity score (DAS) driven step-up protocol aiming at DAS < 2.4. Clinical disease activity measures were collected at baseline, 2, 4, 6, 9 and 12 months, and US examination of the hands was performed at baseline, 6 and 12 months. Grey-Scale (GS) and Power Doppler (PD) synovitis were scored (0 to 3), with overall scores as the sum of each joint score. CXCL13 levels were measured at baseline by enzyme-linked immunosorbent assay and evaluated in relation to the achievement of low disease activity (LDA, DAS < 2.4) and US residual inflammation (PD ≤ 1) at 12 months.ResultsBaseline levels of CXCL13 were significantly higher in RA compared to healthy controls (n = 19) (P = 0.03) and correlated with measures of synovitis, such as the swollen joint count (R 0.28, P < 0.001), the US-GS (R 0.27, P = 0.003) and US-PD (R 0.26, P = 0.005) score. Although CXCL13 did not predict the likelihood of achieving clinical LDA at 12 months within a structured treat-to-target protocol, elevated levels of CXCL13 were associated with more frequent increases of methotrexate dosage (P < 0.001). Using adjusted analyses, the highest levels of CXCL13 (> 100 pg/ml) were the only independent predictor of residual imaging inflammation (P = 0.005), irrespective of initial US-PD scores, disease activity status, acute phase reactants and autoantibodies. Among the patients in clinical LDA at 12 months, US-PD scores ≤ 1 were less frequently achieved in the high baseline CXCL13 (> 100 pg/ml) group, with an adjusted OR = 0.06 (95% CI 0.01 to 0.55, P = 0.01).ConclusionsCXCL13 emerges as a new biological marker in early RA, accurate in assessing the severity of synovitis and the persistence of US-PD activity over time in response to conventional treatments.

Synovial Tissue Heterogeneity and Peripheral Blood Biomarkers

Rheumatoid arthritis is characterized by multiple pathobiological processes and heterogeneous clinical phenotypes. Not surprisingly, the inflamed synovium harbors an equally complex pathology. This includes variability in infiltrating and resident cell populations, spatial arrangements, and cell–cell interactions, as well as gene expression profiles. Remarkable progress in our understanding of the many facets of tissue heterogeneity has been facilitated by the increasing availability of patients’ material and the development of advanced research technologies. The next challenge is to capitalize on the large amount of data generated to elucidate the specific pathogenic pathways disparately activated in different patients and/or different phases of the disease. When tissue pathology can be reliably explored through noninvasive circulating biomarkers, then the circle will be closed. We attempt to highlight key advances in the understanding of synovial tissue heterogeneity in rheumatoid arthritis and summarize novel perspectives in synovial biomarker discovery in relation to peripheral blood.

High expression levels of the B cell chemoattractant CXCL13 in rheumatoid synovium are a marker of severe disease

OBJECTIVE The B cell chemoattractant chemokine ligand 13 (CXCL13) is emerging as a new biochemical marker in RA. This study was undertaken to dissect the relationship between CXCL13 expression levels in the synovium and clinico-pathological variables relevant to RA pathogenesis and outcome. METHODS Synovial tissues from 71 RA patients were evaluated by immunohistochemistry. Thirty paired samples were used for comparative gene expression analysis by quantitative real-time PCR. CXCL13 levels were analysed in relation to cellular, molecular and clinical features of inflammation, lymphocyte activation and joint damage. RESULTS In patients with early disease (<12 months duration), CXCL13 expression correlated significantly with synovial markers of local disease activity and systemic inflammation. Such correlation was less evident in established RA. Notably, the association with lymphocyte infiltration and with expression of B/T cell-related activation and proliferation genes, such as activation-induced cytidine deaminase, IFN-γ and IL-2, remained highly significant independent of disease duration and local disease activity. Patients featuring the highest levels of CXCL13 were more frequently ACPA positive and IgG ACPA titres were increased in the high CXCL13 expression group. Furthermore, the frequency of erosive disease on radiographs was significantly higher in the upper tertile of CXCL13 expression (P = 0.01 with adjustment for disease duration and ACPA). Accordingly, synovial CXCL13 and the local receptor activator of nuclear factor κB ligand (RANKL)/osteoprotegerin (OPG) ratio significantly co-varied (ρ = 0.52, P < 0.01), independent of the level of local inflammation. CONCLUSION Synovial CXCL13 appears to be a marker of a more severe pattern of RA disease, characterized by increased lymphocyte activation and bone remodelling beyond the level of conventional markers of inflammation.

Subclinical remodelling of draining lymph node structure in early and established rheumatoid arthritis assessed by power Doppler ultrasonography

OBJECTIVE To investigate the suitability of power Doppler ultrasonography (PD-US) for the assessment of lymph node (LN) status in RA, evaluating the existence of structural and dynamic modifications in well-characterized stages of the disease. METHODS Ten patients with active disease and five patients in clinical remission underwent complete clinical and PD-US examination of hands, wrists, axillary and cervical LNs on the same day. Synovitis and PD were graded 0-3. LN assessment included maximum short axis, cortical hypertrophy (CH) and PD signal distribution. All patients with active disease were re-evaluated prospectively 3 months after initiation of therapy. RESULTS PD-US signs of axillary LN remodelling were observed in 7 out of 10 patients with active disease despite the absence of clinical lymphoadenopathy. Subclinical alterations were detected in both early untreated RA and in established disease. Characteristic structural changes consisted of hypertrophy of the LN cortex and PD signal amplification in cortical and hilar regions. Cervical LNs in active disease and axillary LNs in clinical remission were unaffected. LN PD amplification returned to normal ranges in patients with baseline alterations re-evaluated 3 months after therapy with TNF-α blocking agents and/or MTX. CONCLUSION Draining LNs in RA are subjected to subclinical intra-parenchymal changes and vascular flow modulation detectable by PD-US. Sonographic signs of LN involvement associate with disease activity and are reversible upon treatment. These data point at LN reactivity as a dynamic component of RA inflammatory cascade and an attractive platform to be explored in prognostic and response to therapy evaluations.

The draining lymph node in rheumatoid arthritis: Current concepts and research perspectives

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease of unknown aetiology, leading to progressive damage of bone and cartilage with functional impairment and disability. Whilst the synovial membrane represents the epicentre of the immune-inflammatory process, there is growing evidence indicating the potential involvement of additional anatomical compartments, such as the lung, bone marrow, and secondary lymphoid tissues. Draining lymph nodes represent the elective site for tissue immune-surveillance, for the generation of adaptive immune responses and a candidate compartment for the maintenance of peripheral tolerance. Despite the precise role of the juxta- and extra-articular lymph node stations in the pathogenesis of RA remaining poorly defined, several lines of research exploiting new technological approaches are now focusing on their assessment as a potential new source of pathobiologic information, biomarkers, and complementary therapeutic targets. In this review we present an updated overview of the main concepts driving lymph node research in RA, highlighting the most relevant findings, current hypothesis, and translational perspectives.

Power Doppler ultrasonographic assessment of the joint-draining lymph node complex in rheumatoid arthritis: a prospective, proof-of-concept study on treatment with tumor necrosis factor inhibitors.

BackgroundEmerging research on the mechanisms of disease chronicity in experimental arthritis has included a new focus on the draining lymph node (LN). Here, we combined clinical-serological analyses and power Doppler ultrasound (PDUS) imaging to delineate noninvasively the reciprocal relationship in vivo between the joint and the draining LN in patients with rheumatoid arthritis (RA).MethodsForty consecutive patients refractory to conventional synthetic disease-modifying anti-rheumatic drugs were examined through parallel PDUS of the hand–wrist joints and axillary LNs and compared with 20 healthy subjects. A semiquantitative score for LN gray-scale (GS) parameters (nodal hypertrophy and cortical structure) and LN PD signal was developed. A 6-month follow-up study with serial sonographic assessments was then performed on initiation of tumor necrosis factor (TNF) inhibitors.ResultsPDUS analysis of RA axillary LNs revealed the existence of marked inter-individual heterogeneity and of quantitative differences compared with healthy individuals in both GS and PD characteristics. RA LN changes were plastic, responsive to anti-TNF treatment, and displayed a degree of concordance with synovitis activity in peripheral joints. However, low LN PD signal at baseline despite active arthritis was strongly associated with a poor clinical response to TNF blockade.ConclusionsPDUS analysis of the draining LN in RA allows capture of measurable inter-individual differences and dynamic changes linked to the underlying pathologic process. LN and joint sonographic assessments are nonredundant approaches that may provide independent perspectives on peripheral disease and its evolution over time.

A5.13 Power-doppler ultrasound assessment of the joint-draining lymph node complex in rheumatoid arthritis

Background and objectives The afferent lymphatic system and the draining lymph node (LN)act as complementary check-points through progressive steps of the inflammatory and resolution processes. We have previously shown in a proof-of-concept study that LN Power Doppler ultrasound (PDUS) allows detection of qualitative changes in rheumatoid arthritis (RA). In this study we developed a quantification approach for PDUS assessment of the inflammatory node and investigated its clinical and pathologic significance. Materials and methods Forty RA patients refractory to conventional DMARDs were evaluated through complete clinical and PDUS examination in hands/wrists and axillary LN. Twenty healthy individuals were recruited as controls. Thirty-one patients starting anti-TNF treatment were followed-up prospectively at weeks 4 and 24. Axillary LN were investigated by digital image analysis and semi-quantitatively focusing on volumetric measures, vascular perfusion and micro-structure of the lymphocyte-rich cortex. Patient-related US indices for each parameter were constructed for correlative, response-to-treatment and predictive analyses. Results LN perfusion and morpho-structural features demonstrated specific quantitative increase in RA LN leading to distinct sonotypes differentiating patients from controls. LN PDUS parameters showed however a high degree of heterogeneity with values exceeding the threshold of controls restricted to 42.5% of the cases. No differences in LN status were observed in relation to autoantibody positivity. LN indices showed instead a link with peripheral joint inflammation as inferred by the significant correlation (at systemic and ipsilateral level) between LN and peripheral joint PD (r = 0.35, p = 0.03). At week 24, 61.3% of the patients were EULAR responders. Patients with different treatment outcomes did not show any significant difference in baseline clinical features and joint US. In contrast, the LN PD index was significantly lower in non-responders (median [IQR] 0 [0–0.5] vs 2 [1–4.75], p = 0.007). Lack of changes of LN PD above the threshold of controls (PD index≤2) was the only predictor of failure to achieve response with an OR of 9.9 (p = 0.04). Conclusions Synchronised and longitudinal PDUS monitoring of joint inflammation and LN reactivity is an achievable goal in patients with RA. Lack of draining LN involvement in patients with active disease seems to associate with a less favourable anti-TNF treatment response.