B cells expressing the IgA receptor FcRL4 participate in the autoimmune response in patients with rheumatoid arthritis.

The clinical efficacy of B cell targeting therapies highlights the pathogenic potential of B cells in inflammatory diseases. Expression of Fc Receptor like 4 (FcRL4) identifies a memory B cell subset, which is enriched in the joints of patients with rheumatoid arthritis (RA) and in mucosa-associated lymphoid tissue. The high level of RANKL production by this B cell subset indicates a unique pathogenic role. In addition, recent work has identified a role for FcRL4 as an IgA receptor, suggesting a potential function in mucosal immunity. Here, the contribution of FcRL4+ B cells to the specific autoimmune response in the joints of patients with RA was investigated. Single FcRL4+ and FcRL4- B cells were sorted from synovial fluid and tissue from RA patients and their immunoglobulin genes characterized. Levels of hypermutation in the variable regions in both populations were largely consistent with memory B cells selected by an antigen- and T cell-dependent process. Recombinant antibodies were generated based on the IgH and IgL variable region sequences and investigated for antigen specificity. A significantly larger proportion of the recombinant antibodies generated from individual synovial FcRL4+ B cells showed reactivity towards citrullinated autoantigens. Furthermore, both in analyses based on heavy chain sequences and flow cytometric detection, FcRL4+ B cells have significantly increased usage of the IgA isotype. Their low level of expression of immunoglobulin and plasma cell differentiation genes does not suggest current antibody secretion. We conclude that these activated B cells are a component of the local autoimmune response, and through their RANKL expression, can contribute to joint destruction. Furthermore, their expression of FcRL4 and their enrichment in the IgA isotype points towards a potential role for these cells in the link between mucosal and joint inflammation.

Periodontitis prevalence and serum antibody reactivity to periodontal bacteria in primary Sjögren's syndrome: a pilot study.

AIMS: The aims of this study were as follows: (i) To assess the prevalence of periodontitis among patients with primary Sjögren's syndrome (pSS) and comparator groups of patients with rheumatoid arthritis (RA) and osteoarthritis (OA). (ii) To perform a pilot study to compare serum antibody responses to 10 oral/periodontal bacteria in these patient groups and a historical comparator group of patients with periodontitis. MATERIALS AND METHODS: Standard clinical periodontal assessments were performed on 39 pSS, 36 RA and 23 OA patients and "In-house" antibody ELISAs for serum antibodies against 10 oral/periodontal bacteria were performed in these groups. RESULTS: Forty-six percent of the pSS group, 64% of the RA group and 48% of the OA group had moderate/severe periodontitis. These frequencies did not reach statistical significance between groups. Raised antibody levels to Prevotella denticola were found in the pSS, RA and periodontitis groups compared to the OA group. Significant between group differences were seen for Aggregatibacter actinomycetemcomitans, Prevotella intermedia and Campylobacter showae. None of these differences were specifically associated with pSS. CONCLUSION: This study showed no increase in periodontitis in pSS patients. Although the P. denticola data are of interest, identifying bacterial triggering factors for pSS will likely require alternative strategies including modern techniques such as microbiome analysis.

Rituximab abrogates joint destruction in rheumatoid arthritis by inhibiting osteoclastogenesis.

OBJECTIVES: To examine how rituximab may result in the inhibition of joint destruction in rheumatoid arthritis (RA) patients. METHODS: Twenty-eight patients with active RA were treated with rituximab. Radiographs of hands and feet before and 1 year after therapy were assessed using the Sharp-van der Heijde score (SHS). Expression of bone destruction markers was evaluated by immunohistochemistry and immunofluorescence of synovial biopsies obtained before and 16 weeks after the initiation of treatment. Serum levels of osteoprotegerin, receptor activator of nuclear factor κB ligand (RANKL), osteocalcin and cross-linked N-telopeptides of type I collagen (NTx) were measured by ELISA before and 16 weeks post-treatment. RESULTS: After 1 year, the mean (SD) change in total SHS was 1.4 (10.0). Sixteen weeks after treatment there was a decrease of 99% in receptor activator of nuclear factor κB-positive osteoclast precursors (p=0.02) and a decrease of 37% (p=0.016) in RANKL expression in the synovium and a trend towards reduced synovial osteoprotegerin expression (25%, p=0.07). In serum, both osteoprotegerin (20%, p=0.001) and RANKL (40%, p<0.0001) levels were significantly reduced 16 weeks after treatment, but the osteoprotegerin/RANKL ratio increased (157%, p=0.006). A trend was found towards an increase of osteocalcin levels (p=0.053), while NTx concentrations did not change. CONCLUSIONS: Rituximab treatment is associated with a decrease in synovial osteoclast precursors and RANKL expression and an increase in the osteoprotegerin/RANKL ratio in serum. These observations may partly explain the protective effect of rituximab on the progression of joint destruction in RA.

The response of T cells to interleukin-6 is differentially regulated by the microenvironment of the rheumatoid synovial fluid and tissue.

OBJECTIVE: Interleukin-6 (IL-6) is a proinflammatory cytokine with regulatory effects on the survival and differentiation of T cells. It exerts its biologic function in 2 ways: by directly binding to the IL-6 receptor (IL-6R; CD126) or via trans-signaling, in which soluble IL-6R/IL-6 complexes bind to the signaling component CD130. This study was undertaken to assess the expression and regulation of CD126 and CD130 and determine how these affect the response of CD4+ T cells to IL-6 in the joints of patients with rheumatoid arthritis (RA). METHODS: Flow cytometry and immunofluorescence microscopy were used to determine the expression, function, and regulation of CD126 and CD130 in CD4+ T cells from the peripheral blood (PB), synovial fluid (SF), and synovial tissue of RA patients. RESULTS: Compared to the findings in RA PB, CD4+ T cells in the SF and synovial tissue expressed low levels of CD126. In contrast, whereas CD4+ T cell expression of CD130 was minimal in the SF, its level in the synovial tissue was high. Consistent with this phenotype, synovial tissue T cells responded to trans-signaling by soluble IL-6R/IL-6 complexes, whereas no response was evident in CD4+ T cells from the SF. Down-regulation of both receptor components in SF T cells could be explained by exposure to high levels of IL-6. Increased levels of CD130 messenger RNA and protein in synovial tissue CD4+ T cells suggested that CD130 is up-regulated locally. Among a range of cytokines tested, only IL-10 induced CD130 expression in T cells. CONCLUSION: The inflamed microenvironment in the synovial tissue maintains responsiveness to IL-6 trans-signaling through the up-regulation of CD130 expression in CD4+ T cells, and this process may be driven by IL-10.

Cytokine mRNA profiling identifies B cells as a major source of RANKL in rheumatoid arthritis.

OBJECTIVES: In rheumatoid arthritis (RA), a complex cytokine network drives chronic inflammation and joint destruction. So far, few attempts have been made to identify the cellular sources of individual cytokines systematically. Therefore, the primary objective of this study was systematically to assess the cytokine messenger RNA expression profiles in the five largest cell populations in the synovial fluid and peripheral blood of RA patients. To reflect the in vivo situation as closely as possible, the cells were neither cultured nor stimulated ex vivo. METHODS: Inflammatory cells from 12 RA patients were sorted into CD4 and CD8 T cells, B cells, macrophages and neutrophils. mRNA expression for 41 cytokines was determined by real-time PCR using microfluidic cards. Receptor activator nuclear factor kappa B ligand (RANKL) (TNFSF11) expression by B cells was further confirmed by flow cytometry and by immunofluorescence staining of frozen sections of synovial tissue from patients with RA. RESULTS: The detection of cytokines characteristic for T cells and myeloid cells in the expected populations validated this methodology. Beyond the expected cytokine patterns, novel observations were made. Striking among these was the high expression of mRNA for RANKL in B cells from synovial fluid. This observation was validated at the protein level in synovial tissue and fluid. CONCLUSIONS: RANKL, the key cytokine driving bone destruction by osteoclast activation, is produced by synovial B cells in RA. This observation is of importance for our understanding of the role of B cells in RA and their therapeutic targeting.

Autoreactive T effector memory differentiation mirrors ß cell function in type 1 diabetes.

In type 1 diabetes, cytotoxic CD8+ T cells with specificity for ß cell autoantigens are found in the pancreatic islets, where they are implicated in the destruction of insulin-secreting ß cells. In contrast, the disease relevance of ß cell-reactive CD8+ T cells that are detectable in the circulation, and their relationship to ß cell function, are not known. Here, we tracked multiple, circulating ß cell-reactive CD8+ T cell subsets and measured ß cell function longitudinally for 2 years, starting immediately after diagnosis of type 1 diabetes. We found that change in ß cell-specific effector memory CD8+ T cells expressing CD57 was positively correlated with C-peptide change in subjects below 12 years of age. Autoreactive CD57+ effector memory CD8+ T cells bore the signature of enhanced effector function (higher expression of granzyme B, killer-specific protein of 37 kDa, and CD16, and reduced expression of CD28) compared with their CD57- counterparts, and network association modeling indicated that the dynamics of ß cell-reactive CD57+ effector memory CD8+ T cell subsets were strongly linked. Thus, coordinated changes in circulating ß cell-specific CD8+ T cells within the CD57+ effector memory subset calibrate to functional insulin reserve in type 1 diabetes, providing a tool for immune monitoring and a mechanism-based target for immunotherapy.

Optimized Peptide-MHC Multimer Protocols for Detection and Isolation of Autoimmune T-Cells.

Peptide-MHC (pMHC) multimers have become the "gold standard" for the detection and isolation of antigen-specific T-cells but recent evidence shows that normal use of these reagents can miss fully functional T-cells that bear T-cell receptors (TCRs) with low affinity for cognate antigen. This issue is particularly pronounced for anticancer and autoimmune T-cells as self-reactive T-cell populations are enriched for low-affinity TCRs due to the removal of cells with higher affinity receptors by immune tolerance mechanisms. Here, we stained a wide variety of self-reactive human T-cells using regular pMHC staining and an optimized technique that included: (i) protein kinase inhibitor (PKI), to prevent TCR triggering and internalization, and (ii) anti-fluorochrome antibody, to reduce reagent dissociation during washing steps. Lymphocytes derived from the peripheral blood of type 1 diabetes patients were stained with pMHC multimers made with epitopes from preproinsulin (PPI), insulin-ß chain, glutamic acid decarboxylase 65 (GAD65), or glucose-6-phospate catalytic subunit-related protein (IGRP) presented by disease-risk allelles HLA A*02:01 or HLA*24:02. Samples from ankylosing spondylitis patients were stained with a multimerized epitope from vasoactive intestinal polypeptide receptor 1 (VIPR1) presented by HLA B*27:05. Optimized procedures stained an average of 40.5-fold (p = 0.01, range between 1.4 and 198) more cells than could be detected without the inclusion of PKI and cross-linking anti-fluorochrome antibody. Higher order pMHC dextramers recovered more cells than pMHC tetramers in parallel assays, and standard staining protocols with pMHC tetramers routinely recovered less cells than functional assays. HLA A*02:01-restricted PPI-specific and HLA B*27:05-restricted VIPR1-specific T-cell clones generated using the optimized procedure could not be stained by standard pMHC tetramer staining. However, these clones responded well to exogenously supplied peptide and endogenously processed and presented epitopes. We also showed that anti-fluorochrome antibody-conjugated magnetic beads enhanced staining of self-reactive T-cells that could not be stained using standard protocols, thus enabling rapid ex vivo isolation of autoimmune T-cells. We, therefore, conclude that regular pMHC tetramer staining is generally unsuitable for recovering self-reactive T-cells from clinical samples and recommend the use of the optimized protocols described herein.

Immunoglobulin characteristics and RNAseq data of FcRL4+ B cells sorted from synovial fluid and tissue of patients with rheumatoid arthritis.

This manuscript is a companion paper to Amara et al. [1]. Data shown here include detailed clinical characteristics from anonymized patients, the Ig subclass data generated from B cells sorted from four individual patients, tables detailing variable gene region sequences from sorted cells linked to the patient information and the sequence yields from individual patients. Furthermore a URL link to the RNAseq datasets submitted to GEO is included.

Metabolic and immune effects of immunotherapy with proinsulin peptide in human new-onset type 1 diabetes.

Immunotherapy using short immunogenic peptides of disease-related autoantigens restores immune tolerance in preclinical disease models. We studied safety and mechanistic effects of injecting human leukocyte antigen-DR4(DRB1*0401)-restricted immunodominant proinsulin peptide intradermally every 2 or 4 weeks for 6 months in newly diagnosed type 1 diabetes patients. Treatment was well tolerated with no systemic or local hypersensitivity. Placebo subjects showed a significant decline in stimulated C-peptide (measuring insulin reserve) at 3, 6, 9, and 12 months versus baseline, whereas no significant change was seen in the 4-weekly peptide group at these time points or the 2-weekly group at 3, 6, and 9 months. The placebo group's daily insulin use increased by 50% over 12 months but remained unchanged in the intervention groups. C-peptide retention in treated subjects was associated with proinsulin-stimulated interleukin-10 production, increased FoxP3 expression by regulatory T cells, low baseline levels of activated ß cell-specific CD8 T cells, and favorable ß cell stress markers (proinsulin/C-peptide ratio). Thus, proinsulin peptide immunotherapy is safe, does not accelerate decline in ß cell function, and is associated with antigen-specific and nonspecific immune modulation.

DKK1 expression by synovial fibroblasts in very early rheumatoid arthritis associates with lymphocyte adhesion in an in vitro flow co-culture system.

BACKGROUND: Synovial fibroblasts play a key role in joint destruction and regulation of the inflammatory infiltrate in established rheumatoid arthritis (RA). The mechanisms by which this occurs in the earliest stages of RA are largely unknown. We investigated the role of Dickkopf-related protein 1 (DKK1) produced by synovial fibroblasts of patients with very early rheumatoid arthritis (VeRA). METHODS: Fibroblasts were isolated from the disease-modifying anti-rheumatic drug-naive Birmingham early arthritis cohort of patients with new onset of clinically apparent arthritis and inflammatory symptoms of ≤12 weeks' duration, who at follow-up had either resolving arthritis or RA. Endothelial fibroblast co-cultures were formed using porous filters, and lymphocyte adhesion to co-cultures was assessed using phase-contrast microscopy. DKK1 gene expression and secretion were quantified by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. RESULTS: Synovial fibroblasts from patients with VeRA expressed significantly higher levels of DKK1 messenger RNA than those from patients with resolving arthritis. A similar trend was observed for DKK1 protein secretion. In co-culture constructs, more DKK1 tended to be secreted in co-cultures incorporating fibroblasts from VeRA than in co-cultures from non-inflamed joints and resolving arthritis. DKK1 secretion during co-culture positively correlated with lymphocyte adhesion. CONCLUSIONS: Alterations in DKK1 could be involved in the pathogenesis and perpetuation of the inflammatory response in the earliest clinically apparent stages of RA.

Differential glucocorticoid metabolism in patients with persistent versus resolving inflammatory arthritis.

INTRODUCTION: Impairment in the ability of the inflamed synovium to generate cortisol has been proposed to be a factor in the persistence and severity of inflammatory arthritis. In the inflamed synovium, cortisol is generated from cortisone by the 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) enzyme. The objective of this study was to determine the role of endogenous glucocorticoid metabolism in the development of persistent inflammatory arthritis. METHODS: Urine samples were collected from patients with early arthritis (symptoms ≤12 weeks duration) whose final diagnostic outcomes were established after clinical follow-up and from patients with established rheumatoid arthritis (RA). All patients were free of disease-modifying anti-rheumatic drugs at the time of sample collection. Systemic measures of glucocorticoid metabolism were assessed in the urine samples by gas chromatography/mass spectrometry. Clinical data including CRP and ESR were also collected at baseline. RESULTS: Systemic measures of 11ß-HSD1 activity were significantly higher in patients with early arthritis whose disease went on to persist, and also in the subgroup of patients with persistent disease who developed RA, when compared with patients whose synovitis resolved over time. We observed a significant positive correlation between systemic 11ß-HSD1 activity and ESR/CRP in patients with established RA but not in any of the early arthritis patients group. CONCLUSIONS: The present study demonstrates that patients with a new onset of synovitis whose disease subsequently resolved had significantly lower levels of systemic 11ß-HSD1 activity when compared with patients whose synovitis developed into RA or other forms of persistent arthritis. Low absolute levels of 11ß-HSD1 activity do not therefore appear to be a major contributor to the development of RA and it is possible that a high total body 11ß-HSD1 activity during early arthritis may reduce the probability of disease resolution.