OBJECTIVES:CASTOR1 senses arginine and regulates mammalian target of rapamycin complex 1 (mTORC1), a central metabolic signaling molecule. This study aimed to elucidate the roles of CASTOR1 in humoral immune responses. METHODS:We analyzed human B cell transcriptomes from healthy controls and patients with systemic lupus erythematosus (SLE) via correlation analysis and gene set variation analysis using our database, Immune Cell Gene Expression Atlas from the University of Tokyo (ImmuNexUT). Castor1-deficient and B cell-specific Castor1-deficient mice were used for analyses of serum immunoglobulins and autoantibodies, urinary proteins, renal pathology, gene expression, and flow cytometry in spleen and bone marrow cells. The culture supernatant of splenic B cells was used for immunoglobulin analysis. RESULTS:Transcriptomic analysis of bulk RNA sequencing data from various B cell subsets in SLE patients (n = 136; n = 129 included in the primary analysis) revealed a correlation between CASTOR1 expression and disease activity, with CASTOR1 expression in plasmablasts inversely correlated with SLEDAI-2K (r = -0.32, p = 0.00031). Castor1-deficient mice exhibited increased plasma cell populations in the spleen and bone marrow, elevated serum IgG levels, production of anti-dsDNA antibodies, and glomerulonephritis with IgG deposits, reflecting SLE-like autoimmunity. Moreover, B cell-specific Castor1-deficient mice showed increased plasma cell counts, elevated serum IgG levels, and glomerulonephritis, indicating that Castor1 might regulate systemic humoral immunity via a B cell-intrinsic mechanism. CONCLUSIONS:CASTOR1 plays a regulatory role in humoral immunity and may contribute to the pathogenesis of autoimmune diseases such as SLE, representing a potential therapeutic target.
OBJECTIVE:Posttraumatic osteoarthritis (PTOA) develops despite restoration of joint biomechanics, suggesting that early post-injury biological processes within the synovium shape disease trajectories. We investigated whether synovial regulatory T (Treg) cells are engaged during the early phase following joint injury and whether experimental enrichment of this compartment is associated with altered local inflammation and PTOA-related pathology. METHODS:Using surgically induced destabilization of the medial meniscus (DMM) and a non-invasive anterior cruciate ligament (ACL) rupture model in mice, we characterized temporal dynamics and phenotypes of synovial Treg cells by high-parameter flow cytometry and integrative single-cell transcriptomic analysis. Treg cells were preferentially expanded using systemic low-dose IL-2/anti-IL-2 complexes or intraarticular adeno-associated virus-mediated IL-2 delivery. Synovial inflammation, cartilage degeneration, and gait function were assessed. RESULTS:Synovial Treg cells accumulated rapidly after joint injury in both models, acquired activation- and tissue-adaptation-associated phenotypes distinct from lymphoid Treg populations, and were associated with local immune-compositional changes. Experimental IL-2-mediated enrichment of the synovial Treg compartment was accompanied by reduced synovitis, attenuated cartilage pathology, and partial improvement in load-bearing gait parameters. CONCLUSION:Early synovial Treg engagement represents a candidate joint-localized immunoregulatory feature of PTOA initiation. Experimental enrichment of this compartment was associated with attenuated PTOA-related features, supporting further investigation of Treg-specific mechanisms and precisely timed, joint-localized immune modulation.
OBJECTIVE:To determine whether down-regulation of the transcription factor Fli1 in myeloid cells, previously implicated in profibrotic programming in systemic sclerosis (SSc), promotes cardiac fibrosis and dysfunction in SSc and to define the underlying mechanisms. METHODS:Immunohistochemistry for Fli1 and galectin-3 (Gal-3) was performed on SSc and control cardiac tissue (n = 6-7). Circulating monocytes were analyzed for Gal-3 protein and messenger RNA (mRNA) levels. Cardiac fibrosis and function were evaluated in young and aged myeloid-specific Fli1 knockout mice (Lyz2Cre/Fli1fl/fl), by collagen staining and echocardiography. Co-culture experiments using human macrophages and primary human cardiac fibroblasts, Fli1 and Gal-3 knockdown, recombinant human Gal-3, and rapamycin were used to dissect mTORC1-dependent profibrotic signaling. RESULTS:Fli1 expression was reduced (~6-fold, P = 0.0103), whereas Gal-3 was increased (~4-fold, P = 0.0031) in SSc myocardium compared with control. SSc monocytes expressed elevated Gal-3 protein (~2-fold, P = 0.0235) and mRNA levels (~1.7-fold, P = 0.0448). Lyz2Cre /Fli1fl/fl mice had increased myocardial collagen and diastolic dysfunction with elevated mitral E/e' (23.79 ± 8.11 vs 18.76 ± 8.09, P = 0.04) but preserved systolic function; in aged mice, fibrosis was further increased, and systolic function was also impaired (left ventricular ejection fraction 47.41 ± 5.07 vs 66.15 ± 11.49, P = 0.0006). Mechanistically, Fli1 loss derepressed the LGALS3 promoter, increasing Gal-3 in macrophages and activating mTORC1 in cardiac fibroblasts, and Gal-3 or mTORC1 inhibition blunted fibroblast activation. CONCLUSION:Fli1 deficiency in myeloid cells drives Gal-3-dependent activation of mTORC1 in cardiac fibroblasts, promoting cardiac fibrosis and dysfunction in SSc. These findings identify a myeloid Fli1-Gal-3-mTORC1 axis as a central pathway in SSc-associated cardiac fibrosis and a potential therapeutic target.
OBJECTIVE:Still's disease (SD) is an autoinflammatory disorder characterized by remarkably high IL-18 levels. Increasing evidence suggests that adaptive immunity also contributes to its pathogenesis, particularly in refractory courses. Macrophage activation syndrome (MAS), one of SD's most severe complications, is associated with further IL-18 elevation and expansion of CD38+HLA-DR+CD8+ T cells. However, whether and when this population emerges during SD remains unknown. We therefore examined CD38+HLA-DR+CD8+ T cells across disease stages. METHODS:CD38+HLA-DR+CD8+ T cells were analyzed longitudinally: at SD-onset (therapy-naïve; n=19), during clinically inactive disease (n=15), and prior to or at MAS occurrence (n=12). Spectral flow cytometry and bulk RNA-sequencing were performed. Correlations with clinical and laboratory parameters were assessed. In vitro cytokine stimulations of healthy donor (HD)-derived PBMCs and CD8+ lymphocytes were performed to explore mechanisms driving differentiation of these cells. RESULTS:CD38+HLA-DR+CD8+ T cells were expanded from SD-onset and peaked in MAS (median: 4.61% and 31.7%, respectively, versus 0.87% in HD). Transcriptomic profiling of these cells revealed enrichment of activation, cytotoxicity, and proliferation programs, which were confirmed at the protein level. Frequencies correlated with markers of systemic inflammation, T-cell activation, and serum IL-18 levels. Sustained IL-18 stimulation in vitro induced robust and persistent expansion of CD38+HLA-DR+CD8+ cells, recapitulating key ex vivo phenotypic features. CONCLUSION:CD38+HLA-DR+CD8+ cells, previously primarily associated with MAS, are detectable early in SD. Persistent IL-18 exposure promotes their expansion. These findings identify CD38+HLA-DR+CD8+ T cells as a potential mechanistic link between SD and MAS and highlight this subset as a candidate therapeutic target.
OBJECTIVE:To assess the association between duration of targeted therapy exposure and cancer risk in patients with spondyloarthritis (SpA), including those with psoriatic arthritis, axial SpA, and other subtypes. METHODS:This nationwide cohort study used the French health insurance database to identify adults with SpA initiating a targeted therapy (TNFi, IL17i, IL12/23i, IL23i, JAKi) from January 2014 to September 2022. Patients with prior cancer, HIV infection, or organ transplantation were excluded. Follow-up began after a 3-month delay and continued until December 2024. Exposure was assessed annually and classified as ≤6 or >6 months per year. Incident cancer was the primary outcome. Weighted Cox marginal structural models with inverse probability of treatment and censoring weights were used. A post hoc sensitivity analysis evaluated cumulative exposure trajectories over time. RESULTS:We included 56,591 patients (53.9% women; mean age 44±13 years; median follow-up 5.0 years). During follow-up, 1,224 cancers occurred (1,029 solid, 116 hematological, 79 unclassified). Exposure >6 versus ≤6 months was associated with a lower risk of overall cancer (weighted HR 0.86, 95%CI 0.75-0.99). In subgroup analyses, this association was observed for hematological malignancies (wHR 0.65, 95%CI 0.42-0.99) but not for solid cancers (wHR 0.92, 95%CI 0.79-1.07). Cumulative exposure history was not associated with cancer risk. CONCLUSION:In this nationwide study, prolonged exposure to targeted therapies was not associated with an increased cancer risk. Exposure >6 months per year was associated with a lower cancer risk, mainly for hematological malignancies, whereas cumulative exposure over multiple years was not associated with cancer risk.
OBJECTIVE:Relapsing polychondritis (RP) is a rare inflammatory disease characterized by recurrent cartilaginous inflammation with unclear pathogenesis. The precise alterations in the peripheral immune landscape driving RP pathogenesis remain incompletely defined. METHODS:Single-cell RNA sequencing was performed on peripheral blood mononuclear cells from six patients with RP and five matched healthy controls. Bioinformatic analyses characterized cellular composition, transcriptomic profiles, differentially expressed genes, pathway enrichment, metabolic states, and intercellular communication. Plasma levels of alarmins and resistin were measured by enzyme-linked immunosorbent assay. RESULTS:Patients with RP exhibited a significant reduction in circulating T cells and a trend toward increased CD14+ monocytes, neutrophils, and plasma cells. Within T cells, we observed expansion of CD8+ subsets and depletion of FCER1G+ T, γδT, and mucosal-associated invariant T cells. Transcriptional programs were indicative of enhanced chemotaxis, activation, differentiation, and interferon responses, alongside cytolytic ability in cytotoxic T subsets. B cells exhibited an activated phenotype, increased plasma cell differentiation potential, and metabolic reprogramming. Myeloid cells display robust up-regulation of alarmins (S100A8/9/12) and proinflammatory pathways. Intercellular communication analysis identified CD14+ monocytes as dominant signaling hubs, exerting extensive crosstalk via annexin, major histocompatibility complex, resistin, and chemokine ligand-receptor pairs, with enrichment of the ANXA1-FPR1 axis. CONCLUSION:This study delineates a comprehensive, cell type-revolved atlas of peripheral immune dysregulation in RP, revealing coordinated alterations in T cell activation and redistribution, B cell differentiation, myeloid-driven inflammation, and prominent alarmin-related signatures. Monocyte-centric signaling networks, potentially orchestrated through the ANXA1-FPR1 pathway, may serve as key amplifiers of systemic inflammation and represent promising targets for therapeutic immune modulation in RP.
OBJECTIVE:Current guidelines recommend anifrolumab and belimumab as comparably viable immunosuppressive therapies for active systemic lupus erythematosus (SLE), yet comparative evidence remains limited. Patients with SLE have increased cardiovascular disease (CVD) risk, with dysregulated type I interferon (IFN-I) signaling implicated in disease pathogenesis. We evaluated whether anifrolumab, an IFN-I receptor antagonist, or belimumab confers differing CVD risks to inform treatment selection and patient counseling. METHODS:We conducted an emulated target trial using electronic health record data from 67 health care organizations in the TriNetX network (2020-2025). Adults with SLE initiating anifrolumab or belimumab without prior CVD were included. Propensity score matching balanced demographics, comorbidities, laboratory data, and medication use. Outcomes included three-year risks of myocardial infarction (MI), heart failure (HF), ischemic stroke, and major adverse cardiovascular events (MACEs). Cox regression estimated hazard ratios (HRs) and 95% confidence intervals (CIs). RESULTS:Before matching, 1,091 patients received anifrolumab and 7,492 received belimumab (mean ages 45.6 and 43.7 years, respectively). After matching, the cohort included 1,084 pairs with mean ages of 45.6 and 46.0 years, respectively. Compared with belimumab, anifrolumab treatment was associated with lower risks of MI (HR 0.63; 95% CI 0.40-0.91), HF (0.55; 0.39-0.75), ischemic stroke (0.50; 0.26-0.94), and MACE (0.65; 0.37-0.89). CONCLUSION:Anifrolumab treatment was associated with lower CVD risk compared with belimumab in patients with SLE, supporting its consideration as a safe therapeutic option, particularly for populations with increased CVD risk. Prospective studies are needed to firmly establish causality.
Despite revolutionary advances in therapeutics for many of the inflammatory rheumatic diseases, osteoarthritis (OA) has not been one of the diseases for which therapy has advanced dramatically, and OA pain frequently remains incompletely controlled. Low dose radiation therapy was commonly used to treat arthritis in the early twentieth century, but it lost currency in the latter years of that century and was not considered to be useful. However there has been a resurgence of interest in its potential utility for the treatment of refractory OA pain. In the last several years, many observational studies have been published suggesting that it may be useful for OA, and the German Society for Radiation Oncology has even disseminated guidelines for its use in OA. Concomitantly, radiation therapists across the United States have made presentations to rheumatology divisions about its availability for this indication and are recommending it for a multitude of patients with painful OA. Close examination reveals that the evidence base for such recommendations is sparse, and accumulating evidence suggests that this modality may not provide incremental benefit over placebo, whereas the placebo effect itself is so potent in OA that it is reasonable to consider the placebo itself as "active" therapy. Unless further evidence is developed through randomized double-blind controlled trials (RDBCTs), rheumatologists should be circumspect about suggesting it for their patients. This Expert Perspective will explore the history of this modality and the data surrounding its use in OA and will provide an evaluation of its potential utility for relieving OA pain.
OBJECTIVE:Although Takayasu arteritis (TAK) is not a prototypical autoantibody-mediated disease, accumulating evidence suggests that B cells are involved. This study aimed to investigate the pathway of B cell activation and its contributions to TAK pathogenesis. METHODS:Histologic analysis of paravascular lymph nodes and affected arteries was conducted to investigate B cell activation pathways in TAK. Bulk RNA-seq, single-cell RNA-seq (scRNA-seq), flow cytometry, and in vitro experiments were performed to characterize the composition, transcriptomic features, and functional profiles of B cells. The numeric and phenotypic alterations induced by tumor necrosis factor (TNF) and JAK inhibition were assessed both in vitro and in four patients with TAK. RESULTS:Histologic (n = 5), flow cytometric (n = 125), and bulk RNA-seq (n = 12) analyses indicated the presence of extrafollicular response and up-regulated age-associated B cell (ABC) production in TAK, along with cross-data set transcriptomic differences between B cells from patients with TAK and systemic lupus erythematosus (SLE). Cross-data set scRNA-seq analysis and in vitro experiments (n = 5) demonstrated that ABC differentiation in TAK was largely uncoupled from antibody-secreting cell (ASC) generation, unlike that in SLE. Functional experiments showed that ABCs exhibited proinflammatory properties, including proinflammatory cytokine production, and that CD11c+ B cells, which contain the ABC compartment, promoted Th17 cell differentiation (n = 6). In vitro, tofacitinib was more effective than adalimumab at reducing ABC proportions and attenuating their proinflammatory phenotype (n = 15), consistent with trends in the exploratory clinical follow-up (n = 4). CONCLUSION:ABCs promote inflammation through proinflammatory functions independent of ASC differentiation in TAK. JAK inhibition exerts distinct suppressive effects on ABCs compared with anti-TNF therapy.
OBJECTIVE:We evaluated baseline characteristics, treatment patterns, and outcomes in patients with systemic autoimmune rheumatic disease-associated progressive pulmonary fibrosis (SARD-PPF) and evaluated whether outcomes differed by SARD subtype. METHODS:The ILD-PRO Registry is a prospective multicenter US registry of patients with PPF. Eligible participants had an ILD other than idiopathic pulmonary fibrosis with reticulation and traction bronchiectasis on high-resolution computed tomography and/or lung biopsy, and met criteria for PPF within the prior 24 months. Among patients with SARD-PPF, we described baseline characteristics and evaluated associations between SARD subtype and clinical outcomes. RESULTS:Among 585 patients with SARD-PPF, physiologic impairment at enrollment was substantial (median FVC 64.5% predicted; median DLco 38.0% predicted); 39.2% used supplemental oxygen, 73.9% were receiving immunomodulatory therapy, and 22.6% were taking nintedanib. By 24 months, 31.3%-62.1% of patients experienced ILD progression across SARD subtypes, and 9.3%-37.6% experienced death or lung transplant. Rheumatoid arthritis-PPF showed the highest unadjusted probability of ILD progression; however, no significant subtype-associated differences were observed in analyses adjusted for age, sex, and/or baseline FVC % predicted. CONCLUSION:In a large prospective multicenter US cohort, SARD-PPF was characterized by advanced physiologic impairment, high treatment burden, and high risk for further progression and death or lung transplant. After accounting for demographic factors and baseline severity, outcomes were broadly similar across SARD diagnoses, supporting phenotype-focused risk stratification and underscoring the need for systematic monitoring and timely optimization of management for SARD-ILD.
Objective The presence of anti–citrullinated protein antibodies in the absence of clinical inflammatory arthritis identifies individuals at risk for rheumatoid arthritis (RA). We examined whether epigenetic remodeling of DNA methylation distinguishes those who ultimately develop RA (“converters”) from individuals who remain asymptomatic (“nonconverters”). Methods Genome‐wide DNA methylation was quantified in peripheral blood mononuclear cells separated into CD4 T memory and naive cells and B cells collected at baseline and longitudinally over up to five years from converters who were anti‐CCP3 positive (n = 21), nonconverters who were anti‐CCP3 positive (n = 50), and controls who were anti‐CCP3 negative (n = 69), as well as patients with early RA (n = 29). Differentially methylated loci (DMLs) were identified, followed by pathway enrichment analysis. Machine‐learning algorithms assessed the predictive value of individual CpG sites for future RA onset. Results At baseline, DMLs clearly separated converters from nonconverters and patients with early RA. Among the pathways associated with differentially methylated genes, enrichment of aberrant NOTCH signaling and DNA repair pathways was particularly prominent in B cells. Longitudinally, methylomes remained stable in controls and nonconverters but underwent progressive remodeling in converters, tracing a “RA methylome trajectory” toward the early RA methylome involving regulatory elements. Machine‐learning models incorporating top CpG predictors accurately classified future converters with RA. Conclusion DNA methylation is a dynamic process that continuously remodels in individuals who were asymptomatic and anti‐CCP3 positive as they progress to disease, whereas it remained relatively stable in nonconverters and controls. Progressive epigenetic remodeling during the trajectory from at risk to clinical arthritis highlights pathogenic pathways and yields biomarkers that may inform prognostic testing and preventive intervention in preclinical RA.
Objective Arthralgia, an early manifestation preceding definite rheumatoid arthritis (RA), represents a critical window to identify high‐risk individuals and implement timely interventions. However, the immunopathologic mechanisms underlying the transition from arthralgia to established RA remain incompletely defined. Methods We employed a multiomics strategy integrating peripheral immune cell phenotyping, serum proteomics, and autoantibody profiling to investigate the immunopathologic continuum from preclinical to established RA. A prospective cohort of 346 patients with recent‐onset arthralgia was enrolled. Participants included healthy controls, self‐limiting arthralgia (SLA), arthralgia at risk of RA (at‐risk individuals, ARI), early RA, and established RA. RA development in ARI was ascertained through 24‐month follow‐up. Results Compared with SLA, ARI showed immune dysregulation, including reduced Treg cells and a lower Treg/Th17 cell ratio, with related changes persisting into early RA. Serum proteomics revealed upregulation of C5, α‐1‐B glycoprotein, RPUSD4, WDR87, and FUBP2, which showed inverse associations with Treg cells. Autoantibody profiling identified stage‐specific reactivity, with ARI showing elevated antibodies against stress‐related proteins. Within 24 months, 18.4% of ARI progressed to RA (converters). Baseline immunophenotypic differences between converters and nonconverters were comparable, whereas longitudinal paired analyses revealed a reduction in Treg cells and Treg/Th17 cell ratio. Treg/Th17 cell ratio (area under the curve [AUC] 0.734) outperformed anti–cyclic citrullinated peptide (CCP; AUC 0.611) in discriminating ARI from SLA, particularly in patients who are anticitrullinated peptide antibodies negative (AUC 0.729). Combining Treg cells, anti‐CCP and Treg/Th17 cell ratio improved classification performance (AUC 0.783). Conclusion These findings delineate a critical transition from reversible immune dysregulation to established autoimmunity along the arthralgia–RA continuum, suggesting that Treg cell–related dysregulation may be associated with progression toward persistent inflammatory arthritis.
Objective To identify autoantibodies in presymptomatic individuals that associate with the onset of rheumatoid arthritis (RA) and to distinguish early RA from osteoarthritis (OA), particularly in individuals lacking classic RA serologic markers. Methods We analyzed serum and plasma from three cohorts: presymptomatic individuals who later developed RA (n = 518), a subset of these at RA diagnosis (n = 241), matched population controls (n = 530), and patients with OA (n = 287). Bead‐based multiplex flow immunoassay detected IgG autoantibodies against joint‐related peptides relevant in arthritis models. Principal component analysis was used to identify subgroups and univariable regression analyses to characterize the performance of autoantibodies with significance for patients with RA negative for anti–cyclic citrullinated peptide (anti‐CCP) and rheumatoid factor (RF), that is, the seronegative RA diagnosis (SeNe) test. Multivariable logistic regression identified autoantibodies with the strongest discriminative power between cases and controls. Results Autoantibody profiles revealed three distinct presymptomatic subgroups, suggesting early immune heterogeneity. The SeNe test was associated with symptom onset within 2.5 years in 13% of anti‐CCP and RF‐negative individuals. Specificity for RA versus OA was 97% (95% confidence interval, 95%–99%). An improved version (SeNe 2.0) identified 16% of anti‐CCP and RF‐negative presymptomatic individuals with 98% specificity versus population controls. Two of five SeNe 2.0 autoantibodies were associated with the presymptomatic state in the multivariable model, including RF and anti‐CCP. Conclusion These novel biomarkers can identify presymptomatic, seronegative individuals at high risk of RA onset and support their recruitment into trials for personalized prevention. Additionally, they distinguish early seronegative RA from OA with high specificity. image
