[Bone mineral density in women with rheumatoid arthritis: A link between immune and biochemical markers].

AIM: To study the association of bone mineral density (BMD) with serum biochemical and immunological markers in postmenopausal women with rheumatoid arthritis (RA). MATERIALS AND METHODS: The study included 173 women with RA (age 61.0 [56.0; 66.0] years). A survey, dual-energy X-ray absorptiometry to measure the BMD of the lumbar spine (LI-LIV), femoral neck (FN) and total hip (TH), routine blood chemistry, measurement of C-reactive protein (CRP), rheumatoid factor, cyclic citrullinated peptide antibodies (CCPA), parathyroid hormone (PTH), vitamin D3, myostatin, follistatin, interleukin-6 (IL-6), IL-6 receptors, insulin-like growth factor 1, adiponectin, leptin, fibroblast growth factor 23, and tumor necrosis factor SF12 were performed. RESULTS: PTH (ß=-0.22, -0.35 and -0.30 for LI-LIV, FN and TH, respectively), CRP (ß=-0.18, 0.23 and -0.22 for LI-LIV, FN and TH, respectively) and leptin (ß=0.35, 0.32 and 0.42 for LI-LIV, FN and TH, respectively) were shown a significant association with BMD in all sites of measurement. It was independent of age, body mass index and postmenopause duration. Associations were also found between adiponectin and BMD of LI-LIV and TH (ß=-0.36 and -0.28, respectively), CCPA and BMD of FN and TH (ß=-0.21, -0.24, respectively) and IL-6 and BMD of FN (ß=0.37). CONCLUSION: The study of biochemical and immunological markers in women with RA demonstrated that CRP, CCPA, PTH, IL-6, adiponectin, and leptin influenced BMD.

Prognostic models of drug-induced neutralizing antibody formation in patients with rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis treated with TNF-α blockersockers.

AIM: This study aimed to construct prognostic mathematical models utilizing multifactorial regression analysis to assess the risk of developing drug-induced neutralizing antibodies in patients with rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis treated with tumor necrosis factor alpha blockers.

Association between serum antinuclear antibody and rheumatoid arthritis.

Background: The relationship between serum antinuclear antibody (ANA) and rheumatoid arthritis (RA) remains unknown. Therefore, we aimed to evaluate whether serum ANA was associated with an increased risk of RA in a case-control study. Methods: Patients with rheumatoid arthritis hospitalized at Shandong Provincial Hospital from January 2018 to December 2022 were recruited as the case group, and patients with other types of arthritis and healthy people at the same time were taken as the control group. Antinuclear antibody (ANA) was detected by indirect immunofluorescence assays. Propensity score matching was employed to construct a cohort of patients exhibiting comparable baseline characteristics. The relationship between serum ANA and the risk of rheumatoid arthritis was analyzed by logistic regression analysis. Results: A total of 1,175 patients with RA and 1,662 control subjects were included in this study. After adjusting for potential confounding factors in the propensity-score matched cohort, the risk of RA gradually increased with rising of ANA titers. When ANA titers were divided into three groups (1:100, 1:320, and 1:1,000), the OR (95% CI) for ANA titers from low to high was 3.95 (3.01, 5.18), 16.63 (9.44, 29.30), and 17.34 (9.53, 31.54), respectively, compared to those when ANA was negative. The ANA patterns closely related to the occurrence of RA include nuclear homogeneous, nuclear speckled, and cytoplasmic speckled. Among them, the positive rate of nuclear homogeneous was the highest, which accounted for 42.64%. The OR (95% CI) of ANA patterns including nuclear homogeneous, nuclear speckled, and cytoplasmic speckled was 16.81 (11.46, 24.65), 3.40 (2.49, 4.63), and 3.09 (1.77, 5.40), respectively. Conclusion: There was a curve relation between ANA titer and RA, and the higher the ANA titer, the higher the probability of RA. However, there was no statistical difference in probability of RA for 1:320 versus 1:1,000 ANA titers. The most important kind of ANA pattern in the blood of RA patients was nuclear homogeneous. These findings suggest that ANA may be a novel risk marker for RA.

Recombinant Human Proteoglycan Aggrecan-G1 Domain-induced Arthritis (GIA) Mouse Model.

The recombinant human proteoglycan aggrecan-G1 domain (rhG1)-induced arthritis (GIA) mouse model is a complex model of rheumatoid arthritis (RA). In GIA, autoimmune arthritis is induced by repeated intraperitoneal immunization of genetically susceptible BALB/c mice with the rhG1 antigen emulsified in the adjuvant dimethyldioctadecylammonium (DDA). This article describes the steps for producing and purifying the rhG1 antigen, the immunization protocol, methods for following the clinical picture of arthritis, and the evaluation of relevant laboratory parameters. In this model, the autoimmune arthritis develops stepwise, similar to RA: First is the preclinical stage (after the first immunization, days 0-20) with no sign of inflammation but detectable T and B cell activation; next, the stage of early arthritis (after the second immunization, days 21-41), where the first definitive signs of arthritis appear together with autoantibody production; and then the severe late-stage arthritis (after the third immunization, after day 42), which presents with massive inflammation of the limbs, leading to cartilage and bone destruction and finally ankylosis. The protocols described here provide sufficient information for investigators to use the GIA model to study different aspects of autoimmune arthritis. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Induction of recombinant human proteoglycan aggrecan-G1 domain (rhG1)-induced arthritis (GIA) Support Protocol 1: Production of rhG1-Xa-mFc2a fusion protein with CHOK1 mammalian expression system Support Protocol 2: Purification of the rhG1-Xa-mFc2a fusion protein by affinity chromatography Support Protocol 3: Preparation of DDA adjuvant Support Protocol 4: Clinical assessment of arthritis Support Protocol 5: Measurement of serum antibody levels and cytokines Support Protocol 6: Measurement of rhG1-induced proliferation and cytokine production in spleen cell culture Support Protocol 7: Histological assessment of arthritic limbs Support Protocol 8: Evaluation of arthritis with micro-computed tomography.

The efficacy and safety of short-term and low-dose IL-2 combined with tocilizumab to treat rheumatoid arthritis.

Background: Immunotherapy targeting factors related to immune imbalance has been widely employed for RA treatment. This study aimed to evaluate the efficacy and safety of low-dose interleukin (IL)-2 combined with tocilizumab (TCZ), a biologics targeting IL-6, in RA patients. Methods: Fifty adults with active RA who met the criteria with complete clinical data were recruited, and divided into three groups: control group (n=15), IL-2 group (n=26), and IL-2+TCZ group (n=9). In addition to basic treatment, participants in the IL-2 group received IL-2 (0.5 MIU/day), while participants in the IL-2+TCZ group received IL-2 (0.5 MIU/day) along with one dose of TCZ (8 mg/kg, maximum dose: 800 mg). All subjects underwent condition assessment, laboratory indicators and safety indicators detection, and records before treatment and one week after treatment. Results: Compared with the baseline, all three groups showed significant improvement in disease conditions, as evidenced by significantly reduced disease activity indicators. The low-dose IL-2 and combination treatment groups demonstrated a violent proliferation of Tregs, while the absolute number of Th1, Th2, and Th17 cells in the latter group showed a decreasing trend. The decrease in the Th17/Treg ratio was more pronounced in the IL-2+TCZ groups. No significant adverse reactions were observed in any of the patients. Conclusion: Exogenous low doses of IL-2 combined TCZ were found to be safe and effective in reducing effector T cells and appropriately increasing Treg levels in RA patients with high effector T cell levels. This approach helps regulate immune homeostasis and contributes to the prevention of disease deterioration. Clinical trial registration: https://www.chictr.org.cn/showprojEN.html?proj=13909, identifier ChiCTR-INR-16009546.

Gene association analysis to determine the causal relationship between immune-mediated inflammatory diseases and frozen shoulder.

Multiple studies have indicated a potential correlation between immune-mediated inflammatory diseases (IMIDs) and Frozen shoulder (FS). To explore the genetic causal relationship between IMIDs and FS using 2-sample Mendelian randomization (MR) analysis. Genome-wide association study (GWAS) summary data for FS were obtained from Green's study, while data for 10 IMIDs were sourced from the FinnGen Consortium. The MR analysis was performed using inverse variance weighting, MR Egger, and weighted median methods. IVW, as the primary MR analysis technique, was complemented with other sensitivity analyses to validate the robustness of the results. Additionally, reverse MR analysis was further conducted to investigate the presence of reverse causal relationships. In the forward MR analysis, genetically determined 4 IMIDs are causally associated with FS: rheumatoid arthritis (odds ratio [OR] (95% confidence interval [95% CI]) = 1.05 [1.02-1.09], P < .01); type 1 diabetes (OR [95% CI] = 1.06 [1.03-1.09], P < .01); hypothyroidism (OR [95% CI] = 1.07 [1.01-1.14], P = .02); and Celiac disease (OR [95% CI] = 1.02 [1.01-1.04], P = .01). However, no causal relationship was found between 6 IMIDs (autoimmune hyperthyroidism, Crohn disease, ulcerative colitis, psoriasis, sicca syndrome and systemic lupus erythematosus) and FS. Sensitivity analyses did not detect any heterogeneity or horizontal pleiotropy. In the reverse MR analysis, no causal relationship was observed between FS and IMIDs. In conclusion, this MR study suggests a potential causal relationship between rheumatoid arthritis, type 1 diabetes, hypothyroidism, and Celiac disease in the onset and development of FS. Nevertheless, more basic and clinical research will be needed in the future to support our findings.

The role of platelets in central hubs of inflammation: A literature review.

Platelets are increasingly recognized for their multifaceted roles in inflammation beyond their traditional involvement in haemostasis. This review consolidates knowledge on platelets as critical players in inflammatory responses. This study did an extensive search of electronic databases and identified studies on platelets in inflammation, focusing on molecular mechanisms, cell interactions, and clinical implications, emphasizing recent publications. Platelets contribute to inflammation via surface receptors, release of mediators, and participation in neutrophil extracellular trap formation. They are implicated in diseases like atherosclerosis, rheumatoid arthritis, and sepsis, highlighting their interaction with immune cells as pivotal in the onset and resolution of inflammation. Platelets are central to regulating inflammation, offering new therapeutic targets for inflammatory diseases. Future research should explore specific molecular pathways of platelets in inflammation for therapeutic intervention.

Targeting pathogenic fibroblast-like synoviocyte subsets in rheumatoid arthritis.

Fibroblast-like synoviocytes (FLSs) play a central role in RA pathogenesis and are the main cellular component in the inflamed synovium of patients with rheumatoid arthritis (RA). FLSs are emerging as promising new therapeutic targets in RA. However, fibroblasts perform many essential functions that are required for sustaining tissue homeostasis. Direct targeting of general fibroblast markers on FLSs is challenging because fibroblasts in other tissues might be altered and side effects such as reduced wound healing or fibrosis can occur. To date, no FLS-specific targeted therapies have been applied in the clinical management of RA. With the help of high-throughput technologies such as scRNA-seq in recent years, several specific pathogenic FLS subsets in RA have been identified. Understanding the characteristics of these pathogenic FLS clusters and the mechanisms that drive their differentiation can provide new insights into the development of novel FLS-targeting strategies for RA. Here, we discuss the pathogenic FLS subsets in RA that have been elucidated in recent years and potential strategies for targeting pathogenic FLSs.

cGAS-STING pathway in pathogenesis and treatment of osteoarthritis and rheumatoid arthritis.

Osteoarthritis (OA) and Rheumatoid Arthritis (RA) are significant health concerns with notable prevalence and economic impact. RA, affecting 0.5% to 1.0% of the global population, leads to chronic joint damage and comorbidities. OA, primarily afflicting the elderly, results in joint degradation and severe pain. Both conditions incur substantial healthcare expenses and productivity losses. The cGAS-STING pathway, consisting of cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING), is a crucial component of mammalian immunity. This pathway is responsible for detecting foreign DNA, particularly double-stranded DNA (dsDNA), triggering innate immune defense responses. When cGAS recognizes dsDNA, it catalyzes the synthesis of cyclic GMP-AMP (cGAMP), which then binds to and activates STING. Activated STING, in turn, initiates downstream signaling events leading to the production of interferons and other immune mediators. The cGAS-STING pathway is essential for defending against viral infections and maintaining cellular balance. Dysregulation of this pathway has been implicated in various inflammatory diseases, including arthritis, making it a target for potential therapeutic interventions. Understanding the intricate molecular signaling network of cGAS-STING in these arthritis forms offers potential avenues for targeted therapies. Addressing these challenges through improved early detection, comprehensive management, and interventions targeting the cGAS-STING pathway is crucial for alleviating the impact of OA and RA on individuals and healthcare systems. This review offers an up-to-date comprehension of the cGAS-STING pathway's role in the development and therapeutic approaches for these arthritis types.

Clinical Phenotypes, Serological Biomarkers, and Synovial Features Defining Seropositive and Seronegative Rheumatoid Arthritis: A Literature Review.

Rheumatoid arthritis (RA) is a chronic autoimmune disorder which can lead to long-term joint damage and significantly reduced quality of life if not promptly diagnosed and adequately treated. Despite significant advances in treatment, about 40% of patients with RA do not respond to individual pharmacological agents and up to 20% do not respond to any of the available medications. To address this large unmet clinical need, several recent studies have focussed on an in-depth histological and molecular characterisation of the synovial tissue to drive the application of precision medicine to RA. Currently, RA patients are clinically divided into "seropositive" or "seronegative" RA, depending on the presence of routinely checked antibodies. Recent work has suggested that over the last two decades, long-term outcomes have improved significantly in seropositive RA but not in seronegative RA. Here, we present up-to-date differences in epidemiology, clinical features, and serological biomarkers in seronegative versus seropositive RA and discuss how histological and molecular synovial signatures, revealed by recent large synovial biopsy-based clinical trials, may be exploited to refine the classification of RA patients, especially in the seronegative group.

Case report: Recombinant human type II tumour necrosis factor receptor-antibody fusion protein induced occult hepatitis B virus reactivation leading to liver failure.

Recombinant human type II tumour necrosis factor receptor-antibody fusion protein (rh TNFR:Fc) is an immunosuppressant approved for treating rheumatoid arthritis (RA). This case report describes a case of hepatitis B reactivation in a patient with drug-induced acute-on-chronic liver failure. A 58-year-old woman with a history of RA was treated with rh TNFR:Fc; and then subsequently received 25 mg rh TNFR:Fc, twice a week, as maintenance therapy. No anti-hepatitis B virus (HBV) preventive treatment was administered. Six months later, she was hospitalized with acute jaundice. HBV reactivation was observed, leading to acute-on-chronic liver failure. After active treatment, the patient's condition improved and she recovered well. Following careful diagnosis and treatment protocols are essential when treating RA with rh TNFR:Fc, especially in anti-hepatitis B core antigen antibody-positive patients, even when the HBV surface antigen and the HBV DNA are negative. In the case of HBV reactivation, liver function parameters, HBV surface antigen and HBV DNA should be closely monitored during treatment, and antiviral drugs should be used prophylactically when necessary, as fatal hepatitis B reactivation may occur in rare cases. A comprehensive evaluation and medication should be administered in a timely manner after evaluating the patient's physical condition and closely monitoring the patient.

Expression and diagnostic value of interleukin-22 in rheumatoid arthritis-associated interstitial lung disease.

Rheumatoid arthritis-associated interstitial lung disease (RA-ILD) is characterized by a high incidence and mortality rate, highlighting the need for biomarkers to detect ILD early in RA patients. Previous studies have shown the protective effects of Interleukin-22 (IL-22) in pulmonary fibrosis using mouse models. This study aims to assess IL-22 expression in RA-ILD to validate foundational experiments and explore its diagnostic value. The study included 66 newly diagnosed RA patients (33 with ILD, 33 without ILD) and 14 healthy controls (HC). ELISA was utilized to measure IL-22 levels and perform intergroup comparisons. The correlation between IL-22 levels and the severity of RA-ILD was examined. Logistic regression analysis was employed to screen potential predictive factors for RA-ILD risk and establish a predictive nomogram. The diagnostic value of IL-22 in RA-ILD was assessed using ROC. Subsequently, the data were subjected to 30-fold cross-validation. IL-22 levels in the RA-ILD group were lower than in the RA-No-ILD group and were inversely correlated with the severity of RA-ILD. Logistic regression analysis identified IL-22, age, smoking history, anti-mutated citrullinated vimentin antibody (MCV-Ab), and mean corpuscular hemoglobin concentration (MCHC) as independent factors for distinguishing between the groups. The diagnostic value of IL-22 in RA-ILD was moderate (AUC = 0.75) and improved when combined with age, smoking history, MCV-Ab and MCHC (AUC = 0.97). After 30-fold cross-validation, the average AUC was 0.886. IL-22 expression is dysregulated in the pathogenesis of RA-ILD. This study highlights the potential of IL-22, along with other factors, as a valuable biomarker for assessing RA-ILD occurrence and progression.

Individual and population-level variability in HLA-DR associated immunogenicity risk of biologics used for the treatment of rheumatoid arthritis.

Hypothesis: While conventional in silico immunogenicity risk assessments focus on measuring immunogenicity based on the potential of therapeutic proteins to be processed and presented by a global population-wide set of human leukocyte antigen (HLA) alleles to T cells, future refinements might adjust for HLA allele frequencies in different geographic regions or populations, as well for as individuals in those populations. Adjustment by HLA allele distribution may reveal risk patterns that are specific to population groups or individuals, which current methods that rely on global-population HLA prevalence may obscure. Key findings: This analysis uses HLA frequency-weighted binding predictions to define immunogenicity risk for global and sub-global populations. A comparison of assessments tuned for North American/European versus Japanese/Asian populations suggests that the potential for anti-therapeutic responses (anti-therapeutic antibodies or ATA) for several commonly prescribed Rheumatoid Arthritis (RA) therapeutic biologics may differ, significantly, between the Caucasian and Japanese populations. This appears to align with reports of differing product-related immunogenicity that is observed in different populations. Relevance to clinical practice: Further definition of population-level (regional) and individual patient-specific immunogenic risk profiles may enable prescription of the RA therapeutic with the highest probability of success to each patient, depending on their population of origin and/or their individual HLA background. Furthermore, HLA-specific immunogenicity outcomes data are limited, thus there is a need to expand HLA-association studies that examine the relationship between HLA haplotype and ATA in the clinic.

Comparative single-cell multiplex immunophenotyping of therapy-naive patients with rheumatoid arthritis, systemic sclerosis, and systemic lupus erythematosus shed light on disease-specific composition of the peripheral immune system.

Introduction: Systemic autoimmune diseases (SADs) are a significant burden on the healthcare system. Understanding the complexity of the peripheral immunophenotype in SADs may facilitate the differential diagnosis and identification of potential therapeutic targets. Methods: Single-cell mass cytometric immunophenotyping was performed on peripheral blood mononuclear cells (PBMCs) from healthy controls (HCs) and therapy-naive patients with rheumatoid arthritis (RA), progressive systemic sclerosis (SSc), and systemic lupus erythematosus (SLE). Immunophenotyping was performed on 15,387,165 CD45+ live single cells from 52 participants (13 cases/group), using an antibody panel to detect 34 markers. Results: Using the t-SNE (t-distributed stochastic neighbor embedding) algorithm, the following 17 main immune cell types were determined: CD4+/CD57- T cells, CD4+/CD57+ T cells, CD8+/CD161- T cells, CD8+/CD161+/CD28+ T cells, CD8dim T cells, CD3+/CD4-/CD8- T cells, TCRγ/δ T cells, CD4+ NKT cells, CD8+ NKT cells, classic NK cells, CD56dim/CD98dim cells, B cells, plasmablasts, monocytes, CD11cdim/CD172dim cells, myeloid dendritic cells (mDCs), and plasmacytoid dendritic cells (pDCs). Seven of the 17 main cell types exhibited statistically significant frequencies in the investigated groups. The expression levels of the 34 markers in the main populations were compared between HCs and SADs. In summary, 59 scatter plots showed significant differences in the expression intensities between at least two groups. Next, each immune cell population was divided into subpopulations (metaclusters) using the FlowSOM (self-organizing map) algorithm. Finally, 121 metaclusters (MCs) of the 10 main immune cell populations were found to have significant differences to classify diseases. The single-cell T-cell heterogeneity represented 64MCs based on the expression of 34 markers, and the frequency of 23 MCs differed significantly between at least twoconditions. The CD3- non-T-cell compartment contained 57 MCs with 17 MCs differentiating at least two investigated groups. In summary, we are the first to demonstrate the complexity of the immunophenotype of 34 markers over 15 million single cells in HCs vs. therapy-naive patients with RA, SSc, and SLE. Disease specific population frequencies or expression patterns of peripheral immune cells provide a single-cell data resource to the scientific community.

Protein Citrullination by Peptidyl Arginine Deiminase/Arginine Deiminase Homologs in Members of the Human Microbiota and Its Recognition by Anti-Citrullinated Protein Antibodies.

The human microbiome exists throughout the body, and it is essential for maintaining various physiological processes, including immunity, and dysbiotic events, which are associated with autoimmunity. Peptidylarginine deiminase (PAD) enzymes can citrullinate self-proteins related to rheumatoid arthritis (RA) that induce the production of anti-citrullinated protein antibodies (ACPAs) and lead to inflammation and joint damage. The present investigation was carried out to demonstrate the expression of homologs of PADs or arginine deiminases (ADs) and citrullinated proteins in members of the human microbiota. To achieve the objective, we used 17 microbial strains and specific polyclonal antibodies (pAbs) of the synthetic peptide derived from residues 100-200 of human PAD2 (anti-PAD2 pAb), and the recombinant fragment of amino acids 326 and 611 of human PAD4 (anti-PAD4 pAb), a human anti-citrulline pAb, and affinity ACPAs of an RA patient. Western blot (WB), enzyme-linked immunosorbent assay (ELISA), elution, and a test with Griess reagent were used. This is a cross-sectional case-control study on patients diagnosed with RA and control subjects. Inferential statistics were applied using the non-parametric Kruskal-Wallis test and Mann-Whitney U test generated in the SPSS program. Some members of phyla Firmicutes and Proteobacteria harbor homologs of PADs/ADs and citrullinated antigens that are reactive to the ACPAs of RA patients. Microbial citrullinome and homolog enzymes of PADs/ADs are extensive in the human microbiome and are involved in the production of ACPAs. Our findings suggest a molecular link between microorganisms of a dysbiotic microbiota and RA pathogenesis.

Macrophage polarization in rheumatoid arthritis: signaling pathways, metabolic reprogramming, and crosstalk with synovial fibroblasts.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by persistent synovial inflammation and progressive joint destruction. Macrophages are key effector cells that play a central role in RA pathogenesis through their ability to polarize into distinct functional phenotypes. An imbalance favoring pro-inflammatory M1 macrophages over anti-inflammatory M2 macrophages disrupts immune homeostasis and exacerbates joint inflammation. Multiple signaling pathways, including Notch, JAK/STAT, NF-κb, and MAPK, regulate macrophage polarization towards the M1 phenotype in RA. Metabolic reprogramming also contributes to this process, with M1 macrophages prioritizing glycolysis while M2 macrophages utilize oxidative phosphorylation. Redressing this imbalance by modulating macrophage polarization and metabolic state represents a promising therapeutic strategy. Furthermore, complex bidirectional interactions exist between synovial macrophages and fibroblast-like synoviocytes (FLS), forming a self-perpetuating inflammatory loop. Macrophage-derived factors promote aggressive phenotypes in FLS, while FLS-secreted mediators contribute to aberrant macrophage activation. Elucidating the signaling networks governing macrophage polarization, metabolic adaptations, and crosstalk with FLS is crucial to developing targeted therapies that can restore immune homeostasis and mitigate joint pathology in RA.

Increased interleukin-26 in the peripheral joints of patients with axial spondyloarthritis and psoriatic arthritis, co-localizing with CD68-positive synoviocytes.

Objectives: IL26 levels are elevated in the blood and synovial fluid of patients with inflammatory arthritis. IL26 can be produced by Th17 cells and locally within joints by tissue-resident cells. IL26 induces osteoblast mineralization in vitro. As osteoproliferation and Th17 cells are important factors in the pathogenesis of axial spondyloarthritis (axSpA), we aimed to clarify the cellular sources of IL26 in spondyloarthritis. Methods: Serum, peripheral blood mononuclear cells (n = 15-35) and synovial tissue (n = 3-9) of adult patients with axSpA, psoriatic arthritis (PsA) and rheumatoid arthritis (RA) and healthy controls (HCs, n = 5) were evaluated by ELISA, flow cytometry including PrimeFlow assay, immunohistochemistry and immunofluorescence and quantitative PCR. Results: Synovial tissue of axSpA patients shows significantly more IL26-positive cells than that of HCs (p < 0.01), but numbers are also elevated in PsA and RA patients. Immunofluorescence shows co-localization of IL26 with CD68, but not with CD3, SMA, CD163, cadherin-11, or CD90. IL26 is elevated in the serum of RA and PsA (but not axSpA) patients compared with HCs (p < 0.001 and p < 0.01). However, peripheral blood CD4+ T cells from axSpA and PsA patients show higher positivity for IL26 in the PrimeFlow assay compared with HCs. CD4+ memory T cells from axSpA patients produce more IL26 under Th17-favoring conditions (IL-1ß and IL-23) than cells from PsA and RA patients or HCs. Conclusion: IL26 production is increased in the synovial tissue of SpA and can be localized to CD68+ macrophage-like synoviocytes, whereas circulating IL26+ Th17 cells are only modestly enriched. Considering the osteoproliferative properties of IL26, this offers new therapeutic options independent of Th17 pathways.

The chromatin landscape of pathogenic transcriptional cell states in rheumatoid arthritis.

Synovial tissue inflammation is a hallmark of rheumatoid arthritis (RA). Recent work has identified prominent pathogenic cell states in inflamed RA synovial tissue, such as T peripheral helper cells; however, the epigenetic regulation of these states has yet to be defined. Here, we examine genome-wide open chromatin at single-cell resolution in 30 synovial tissue samples, including 12 samples with transcriptional data in multimodal experiments. We identify 24 chromatin classes and predict their associated transcription factors, including a CD8 + GZMK+ class associated with EOMES and a lining fibroblast class associated with AP-1. By integrating with an RA tissue transcriptional atlas, we propose that these chromatin classes represent 'superstates' corresponding to multiple transcriptional cell states. Finally, we demonstrate the utility of this RA tissue chromatin atlas through the associations between disease phenotypes and chromatin class abundance, as well as the nomination of classes mediating the effects of putatively causal RA genetic variants.