Journal of Allergy and Clinical Immunology

RationaleEosinophilic airway inflammation is common in severe asthma and strongly associated with symptoms, exacerbations, and impaired lung function. Although type 2 (T2)-targeted biologics improve outcomes and reduce eosinophils, many patients experience residual symptoms and exacerbations. Emerging evidence suggests that these biologics may differentially affect specific airway eosinophil subpopulations, representing a potential mechanism of suboptimal treatment response. ObjectiveDetermine the effect of biologic treatment on eosinophil subpopulations in adults with severe asthma using in-depth immune profiling with mass cytometry (CyTOF). MethodsFifty adults with severe asthma (28 biologic-naive, 22 on stable-dose biologic therapy for [&ge;]6 months) underwent clinical phenotyping, spirometry, blood sampling, and sputum induction. Twenty-nine sputum samples passed quality control thresholds and were profiled by CyTOF. Manually gated sputum eosinophils were clustered using FlowSOM to identify eosinophil subpopulations, and cluster abundances and marker expression were compared across treatment groups. Measurements and Main ResultsCyTOF revealed treatment-associated shifts in circulating immune cells (lower CD4+ T cells and B cells, higher monocytes) and lower sputum CD8+ T cells. Unsupervised clustering of sputum eosinophils identified eight distinct subpopulations, and selective depletion of Cluster 6 was noted in biologic-treated participants (biologic-naive vs anti-TSLP logFC -4.98, p=0.003; biologic-naive vs anti-IL5 logFC -6.89, p=0.01). Higher Cluster 6 proportion correlated with worse ACT scores (rho = -0.44, p = 0.02) and lung function (FEV1 % predicted: rho = -0.47, p < 0.01; FEV1/FVC: rho = -0.40, p = 0.03). Functionally, Cluster 6 displayed enriched trafficking/activation markers (CCR3/Eotaxin-1, CD69, CD80, CRTH2) and non-T2 inflammatory mediators (TNF, IL-8, TLR7). ConclusionBiologic therapy in severe asthma was associated with selective depletion of a highly activated sputum eosinophil subpopulation with capability to drive both T2 and non-T2 inflammatory pathways. This cluster correlated with worse asthma control and lung function, indicating it may be a biologically important driver of persistent disease and potential biomarker to more accurately predict treatment response.

RationaleAsthma is a multifactorial disease with a role of genetic susceptibility and environmental exposures. These aspects are poorly understood for pediatric obesity-related asthma, a phenotype of non-allergic asthma. ObjectiveTo quantify gene by environment interactions in obesity-related asthma MethodsUsing expression quantitative trait loci (eQTLs) as measure of genetic susceptibility, and obesity-mediated effects on anthropometrics, metabolic measures, and T helper cell proportions as biological sequelae of obesogenic environment, we quantified the association of eQTLs with asthma burden, and its modulation by obesity-mediated effects, in primary cohort of 144 children, and validation cohort of 101 children. Measurements and Main ResultsOf the 3,904 eQTLs associated with gene expression, up to 30% were associated with pulmonary function indices, including FVC, FEV1, TLC, FRC and IC, and were enriched for African ancestry. These eQTLs encoded for antigen presentation, cell mobility, autophagy, small GTPase signal transduction, fatty acid metabolism, and chromosome segregation pathways. Neck and waist circumference, insulin resistance, leptin and adiponectin levels, and T helper 1 and 17 cell proportions attenuated association of up to 51% eQTLs with pulmonary function, which encoded for all but fatty acid metabolism and chromosome segregation pathways. eQTLs associated with ATF6 and MEI1 retained significance. eQTLs for RNASET2, FBLN5, STX2, HEATR3 and SERPINB6 genes were associated with pulmonary function in the validation cohort. ConclusionsWe report novel genetic susceptibility markers of asthma burden in pediatric obesity-related asthma that are enriched for African ancestry and are partly attenuated by truncal fat load and obesity-mediated inflammation and metabolic dysregulation.

Background: Biologically distinct asthma subgroups may obscure genetic effects when analyzed as a single phenotype. We examined whether asthma susceptibility signals are shared, heterogeneous, or stratum-specific across ancestry, obesity status, and sex. Methods: We performed ancestry-specific GWAS meta-analyses in African ancestry participants (9,965 asthma cases; 37,391 controls) and European ancestry participants (6,074 cases; 116,255 controls), followed by obesity- and sex-stratified analyses. Analyses used imputed dosages and fixed-effect meta-analysis within ancestry. Results: Stratification detected asthma association signals that were less apparent in the combined phenotype. Shared cross-ancestry loci implicated epithelial antiviral susceptibility and immune regulation, represented by signals near CDHR3 and FOXO1. An ancestry-heterogeneous signal at the 17q21 locus, harboring ORMDL3/GSDMB, supported population-dependent effects at an epithelial inflammatory locus. Obesity stratification mapped the genome-wide significant burden to asthma without obesity. Sex stratification detected genome-wide significant signals in AFR females with asthma and obesity and in both sex strata with asthma without obesity, with the strongest signal burden in EU females without obesity. Conclusions: Asthma genetic architecture differed by ancestry, obesity status, and sex. Stratified analyses identified group-specific susceptibility related to epithelial and immune regulation, airway inflammation, remodeling, and neural signaling, supporting precision approaches to asthma.

Prediction models for asthma remission in school-age are lacking, limiting clinicians' ability to tailor follow-up. Most prediction tools focus on pre-school diagnosis or require lung function testing. We developed and validated a simple, history-based clinical prediction tool for asthma remission. We analyzed prospective data from the Swiss Paediatric Airway Cohort (SPAC), including 1860 children (aged 5-16 years) with physician-diagnosed asthma. We derived asthma remission predictors from parental questionnaires capturing demographics, symptoms, triggers, and family history. We defined clinical remission at 2-3 years following asthma diagnosis, as absence of wheeze and inhaler use during the past 12 months. We developed the model using LASSO regression with multiple imputations for missing data, and assessed its performance by area under the curve (AUC), Hosmer-Lemeshow (HL) test, and calibration plots. We then derived a simplified score and validated it in the German All-Age Asthma Cohort (ALLIANCE). From 12 candidate variables, the final score retained: sex, wheeze frequency, night-time awakening, exercise-induced wheeze, pollen-triggered wheeze, animal-triggered wheeze, maternal asthma, and paternal asthma. The score demonstrated moderate discrimination in the development cohort (AUC 0.71) and maintained discriminative ability in the external validation (AUC 0.71). This practical, prognostic tool for asthma remission based only on clinical history, allows clinicians to identify children who have lower chances for remission, enabling their closer monitoring.

Obesity increases local inflammatory responses in adipose tissue. Individuals with obesity have increased asthma incidence and severity and reduced responses to asthma therapeutics through unknown mechanisms. To identify mechanisms by which increased fat mass augments asthma pathogenesis, single cell RNA sequencing of the immune-rich stromovascular fraction of subcutaneous adipose tissue was conducted from well-characterized adults with obesity-associated asthma matched to adults without asthma. Individuals with asthma had increased abundance of perivascular macrophages and lymphoid-associated macrophages (LAMs) and reduced abundance of classical monocytes and CD4+ and CD8+ naive T cells. Pseudo-bulk differential expression (DE) identified upregulation of cellular metabolism, specifically oxidative phosphorylation, and decreased immune homeostatic pathways in asthma across immune cell subsets. Cell type specific DE analysis of effector cell subtypes identified significant induction of metallothionein gene expression in asthma, a signature of immune cell dysfunction characterized by both an activation and exhaustion phenotype. Gene co-expression analysis identified gene modules associated with asthma diagnosis, lung function, and biomarkers of type 2 inflammation were enriched in effector cells. These data identify adipose tissue dysfunction occurs in obesity-associated asthma and support adipose tissue as therapeutic target to address the enhanced asthma risk among those with obesity. Grant SupportNIH U01AI155299, P30DK020593, R01AI182159, K23HL159351, UL1RR024975-03, P30CA68485, P30EY08126, G20RR030956, 5UL1TR002243, KL2TR002245, P30AI110527, DK020593, American Heart Association 17SFRN33520017.

Background: GINA-based clinical assessment of asthma control provides limited insight into the molecular mechanisms driving disease progression and treatment response. Circulating microRNAs (miRNAs) are implicated in immune regulation and airway remodeling, but their relationship to longitudinal, treatment-specific asthma control is not well characterized. We aimed to identify treatment-specific miRNAs associated with longitudinal asthma control and evaluate their ability to discriminate well-controlled from uncontrolled asthma. Methods: Baseline serum miRNA sequencing data from 491 children in the Childhood Asthma Management Program (CAMP), a randomized trial of budesonide versus placebo, were analyzed, with GINA-based composite symptom scores assessed at baseline and 2, 4, 8, and 12 months. Cumulative link mixed models were fitted across 266 miRNAs to identify associations with longitudinal ordinal asthma control, adjusting for time, baseline status, and treatment. Random Forest classifiers were trained within each treatment group using Group K-Fold cross-validation. Pathway enrichment of validated miRNA targets was performed with DAVID. Results: In the budesonide group, hsa-miR-1224-5p was associated with lower symptom severity and hsa-miR-199a-3p|hsa-miR-199b-3p with higher severity; both associations persisted at 12 months. The placebo group showed a broader pattern, with ten miRNAs associated with symptoms. Random Forest classifiers achieved mean AUC of 0.776 (budesonide) and 0.714 (placebo) for 12-month control status. Budesonide-associated targets were enriched for glucocorticoid-responsive and MAPK/Ras signaling, while placebo-associated targets showed broad enrichment for general regulatory processes. Conclusion: Treatment-specific circulating miRNAs distinguish asthma control over time and implicate distinct signaling pathways, supporting their potential as complementary molecular markers for asthma monitoring in children.

BackgroundSevere eosinophilic asthma (SEA), eosinophilic granulomatosis with polyangiitis (EGPA) and nasal polyposis (NP) are immune-mediated diseases characterised by eosinophilic inflammation. However, there is also increasing interest in the potential pathological roles of autoantibodies in these diseases. Understanding their B cell receptor (BCR) repertoires may provide valuable insights into disease mechanisms, and potential role of B cells in their pathology. MethodsWe conducted BCR repertoire sequencing using peripheral blood from 43 patients, comprising SEA with nasal polyps (SEA+NP), SEA without nasal polyps (SEA-NP), and EGPA, along with 16 healthy controls (HCs). ResultsCompared to HCs, patients with EGPA exhibited increased relative proportions of IgA1, IgG1, IgG2, and IgG4 subclasses. Similarly, SEA-NP patients demonstrated significantly high proportion of IgG2 sequences. Notably, the IgG4 subclass was significantly elevated across all patient groups compared to HCs. Patients receiving anti-IL-5/5R biologic treatments showed increased relative proportions of IgA2 and IgG2 subclasses compared to untreated patients. Some variation across participant groups in mean somatic hypermutation and mutation frequency was evident. 1,508 clones shared across patients, but not healthy controls, were evident though the majority showed low clonal expansion. Nevertheless, a few shared clones did show either high prevalence across patients and/or higher clonal expansion. ConclusionChanges in BCR repertoires in SEA/EGPA are consistent with a pattern of a more mature B cell component in the periphery and with the T2 inflammatory response observed in SEA and EGPA. BCR clonotypes shared across patients were evident, however, whether such clonotypes are pathological in SEA/EGPA requires further investigation.

Background Early-life respiratory syncytial virus (RSV) infection is associated with childhood recurrent wheeze or asthma (RW/A), but causality and shared genetic liability remain unclear. Methods We combined Finnish nationwide registries and Nordic genetic cohorts. First, in 965 312 Finnish children born between 1998 and 2014, we defined severe RSV as RSV hospitalisation before age 1 year, and recurrent wheezing or asthma (RW/A) as inhaled medication reimbursement between ages 1 and 7 years, and compared medication and eosinophil trajectories by RSV history. Second, we assessed familial confounding in 527 776 full siblings and 15 667 RW/A-discordant pairs. Third, we performed a genome-wide association study (GWAS) of RSV susceptibility with meta-analysis across six Nordic cohorts (3 107 cases, 92 031 controls) and two-sample Mendelian randomisation (2SMR) using 155 asthma-associated variants. Findings RSV-associated RW/A showed higher inhaled medication use at ages 1-2 years but lower use after age 4, and lower mean blood eosinophils (0.34 vs 0.39*10e9/L; p=0.003) than RW/A without RSV hospitalisation. In RW/A-discordant sibling pairs, RSV hospitalisation was associated with RW/A (OR 2.8; 95% CI 2.4-3.2), while unaffected siblings also had elevated RW/A prevalence. GWAS identified an RSV association at APBB1IP (rs787036; beta=0.209; p=8.80*10e-9). 2SMR provided no evidence that asthma genetic liability influenced RSV susceptibility. Interpretation The RSV-asthma association is unlikely to be explained by shared genetic or environmental factors, and RSV-associated RW/A shows a distinct trajectory. These findings help prioritise long-term outcomes for RSV prevention trials and monitoring. Funding: Paivikki and Sakari Sohlberg Foundation, Foundation for Pediatric Research, Sigrid Juselius Foundation, Orion Research Foundation, the Research Council of Norway.

Rationale Airway remodelling (AR) contributes to airflow limitation and poor symptom control in severe asthma. While anti-IL-5 therapy improves clinical outcomes in severe asthma, the cellular and molecular mechanisms underlying its effects on AR remain incompletely understood. Objectives. To determine whether IL-5 blockade directly modulates airway epithelial biology and contributes to attenuation of AR in severe asthma with eosinophilia (SAE). Methods. Patients with SAE underwent bronchoscopy before and after 24 weeks of anti-IL-5 therapy. Paired bronchial brushings (n=12) were analysed using single-cell RNA-sequencing. Histological features of AR were assessed in paired bronchial biopsies (n=16). Functional effects of IL-5 were investigated using wound healing assays in differentiated air-liquid interface (ALI) cultures. Measurements and Main Results. Anti-IL-5 treatment improved clinical outcomes without altering airway epithelial cellular composition. Differential gene expression was predominantly restricted to bronchial ciliated epithelial cells, which expressed IL5RA. ALI cultures showed IL-5R protein. Anti-IL-5 therapy induced a transcriptional signature in ciliated cells that opposed IL-5-responsive genes. Pseudotime analyses demonstrated preserved epithelial differentiation trajectories but altered programmes related to mucus regulation and ion transport. Cell-cell communication analyses revealed decreased T2-inflammatory processes alongside enrichment of epithelial repair and barrier integrity processes after treatment. Functionally, IL-5 directly impaired epithelial wound repair in ALI cultures. Histological assessment demonstrated increased epithelial E-cadherin expression and reduced sub-basement membrane thickness, extracellular matrix deposition and goblet cell hyperplasia in bronchial biopsies. Conclusions. IL-5 blockade modulates epithelial biology at transcriptional, functional and structural levels in SAE and is associated with improved epithelial integrity and reduced features of AR.

Monocytes are critical regulators of allergic inflammation, whose functions are modified by IgE-driven processes. Monocytes are heterogeneous; comprised of multiple subsets which implies differential functions. In allergic inflammation, this heterogeneity is likely influenced by IgE-mediated effects. We sought to identify phenotypically distinct monocyte subsets related to allergic disease and then further delineate functional differences in cytokine release and antiviral responses. Using high dimensional spectral flow cytometry, we identified monocyte surface phenotypes directly related to surface levels of the high affinity IgE receptor (Fc{epsilon}RI) and surface-bound IgE. Fc{epsilon}RI+IgE+ monocytes, or FIMs, correlated with allergic disease and the level of atopy (i.e. serum IgE levels) of individual subjects. The FIM population also had differential surface expression of other molecules of monocyte maturation, which closely resembled a type 2 conventional dendritic cell (cDC2) phenotype. Functionally, FIMs had enhanced antiviral responses and IgE-driven IL-10 cytokine release. Finally, we showed that FIMs could be identified at higher levels in lung tissue from individuals with asthma. This study supports that atopic disease drives differential monocyte phenotypes, with the FIM population, specifically, as a more mature cell population closely related to dendritic cells with enhanced antiviral responses. The presence of monocytes in lung tissue during lethal asthma exacerbation further supports a role in regulating tissue inflammatory responses in allergic airway disease.

Asthma is a chronic inflammatory disease affecting over 300 million people worldwide. This disease has multiple underlying etiologies, and a major endotype of asthma is characterized by cellular and molecular signatures of type 2 (allergic) inflammation. In this study we conducted bronchoscopies with airway segmental allergen challenge in allergic asthmatics to dissect airway responses to allergen. Using mass cytometry and single-cell RNA sequencing, we characterized with high resolution the airway immune landscape before and after allergen challenge and the heterogeneity present between subjects. This heterogeneity generally falls along a type 1/ type 2 axis. In type 2 high individuals, we identified allergen-reactive Th2 cells by using TCR sequences to barcode clonal T cell populations in single-cell genomic and activation-induced marker expression assays. These potentially pathogenic Th2 cell clones were present systemically and expanded following allergen challenge, connecting local lung inflammation to systemic clonal Th2 cell dynamics. Th2 cell airway ingress was coordinated with myeloid cell expression of T cell chemoattractants including CCL17 and CCL22. This study provides insight into the molecular and cellular components of allergen-induced tissue inflammation in asthma. Deeper resolution of the T cell response to aeroallergens may inform novel diagnostic and therapeutic strategies for asthma and other allergic airway diseases.

BackgroundAsthma exacerbations are caused by dysregulated cellular interactions between airway and immune cell populations. Circulating microRNAs (miRNAs) are potential biomarkers for asthma exacerbations; however, their target airway cells remain poorly defined. ObjectiveTo identify the cell types that are regulated by the circulating microRNAs linked to asthma exacerbations and the extent to which the cells are regulated by miRNAs. MethodsWe integrated a curated panel of exacerbation-associated circulating miRNAs with single-cell RNA sequencing (scRNA-seq) profiles from induced sputum of 16 asthma patients and 8 healthy controls. Experimentally validated miRNA-target interactions were combined with cell-type-specific differential expression. Elastic Net regression and SHAP analysis quantified gene-level regulatory contributions, yielding a composite Regulation Strength metric. Findings were validated against four independent GEO datasets. ResultsImmune cells, including monocytes, dendritic cells, and macrophages, demonstrated the strongest statistically significant miRNA regulatory signals, in contrast to airway epithelial cells.hsa-miR-222-3p showed opposing regulatory effects in mature versus alveolar macrophages, indicating differentiation-state-dependent activity, while B_Plasma cells showed no detectable regulatory effect from any miRNA tested. Independent GEO validation confirmed higher expression of protective miRNAs (hsa-miR-126-3p, hsa-miR-146b-5p) in healthy individuals, consistent with prior CAMP cohort associations. ConclusionCirculating miRNAs show cell-type-specific regulatory activity, strongest in monocytes, dendritic cells, and macrophages. hsa-miR-222-3p showed opposing regulatory directions between macrophage subtypes, while B_Plasma cells showed no effect, validated across independent GEO cohorts.

Deficiency of the Interleukin-36 Receptor antagonist (DITRA) is a rare autoinflammatory condition which commonly manifests as severe, recurrent episodes of Generalized Pustular Psoriasis (GPP). Loss-of-function mutations in the IL36RN gene result in unopposed IL-36 cytokine signalling leading to severe psoriatic inflammation, which can be successfully treated with Anti-IL-36 receptor (IL-36R) monoclonal antibodies. Despite such advances, there remain some key questions concerning how loss of a functional IL-36R antagonist predisposes to GPP, including identifying the potential impacts of IL36RN mutations on skin homeostasis. To address this question, we investigated the consequences of IL-36Ra deficiency using Il36rn-/- mice, which recapitulate the severe psoriatic inflammation observed in DITRA patients. Here, we demonstrate, that in overtly healthy Il36rn-/- mice, prior to disease onset, there is disrupted dermal immune homeostasis, characterised by decreased expression of the chemokine CCL27. Altered skin homeostasis occurred in association with dysbiosis of the skin microbiome, characterised by a significant outgrowth of the commensal bacteria, Cutibacterium acnes. Importantly, intradermal administration of recombinant CCL27, prior to disease induction, significantly reduced the enhanced severity of psoriasiform inflammation, demonstrating a central role for this chemokine in regulating predisposition to increased severity. Transcriptomic analysis of GPP patients skin also revealed decreased CCL27 expression in non-lesional, as well as lesional, compared to healthy skin, indicating that this chemokine may also play a key instructive role among DITRA patients. Together, these data identify a novel mechanism through which IL-36Ra deficiency alters dermal homeostasis and predisposes to increased severity of psoriatic disease observed in DITRA patients.

De novo mutations underlying early-onset systemic autoinflammatory diseases have identified key regulators of innate immunity, including pathways that drive IL-1-mmediated inflammation. Here we describe two unrelated girls presenting in infancy with systemic inflammation and sterile lung abscesses, who harbor the same de novo gain-of-function mutation in dysferlin (DYSF; p.P1449L) Myeloid expression of DYSF P1449L enhances COP-I binding, promotes dysferlin retention in the ER-Golgi, and disrupts vesicle trafficking and membrane homeostasis. Dysferlin-mutant monocytes and M2-like macrophages exhibit ectopic perinuclear NLRP3 inflammasome activation, increased IL-1{beta} production, and inflammatory cell death. Mutant M2-like macrophages further display defects in membrane expansion, exocytosis, efferocytosis, and debris clearance, promoting neutrophil recruitment and DAMP-signal amplification that culminate in sterile abscess formation. These findings identify dysferlin as a regulator of membrane homeostasis in myeloid cells, establish defective membrane-stress adaptation as trigger of NLRP3 inflammasome activation, and define a novel IL-1 mediated autoinflammatory disease caused by gain-of-function DYSF mutations.

Background: Short-chain fatty acids (SCFAs) are microbial metabolites with immunoregulatory properties. Human milk contains SCFAs which have been proposed as potential modulators of infant immune development. We aimed to examine associations between human milk SCFA concentrations and infant allergic disease outcomes in a high-risk cohort of infants of atopic mothers. Methods: SCFAs were measured by targeted liquid chromatography-mass spectrometry in human milk samples collected at 3 and 6 months postpartum from atopic mothers enrolled in the Infant Fish Oil Supplementation (IFOS) Study (n=147). Associations between milk SCFA concentrations and early childhood allergic disease outcomes (atopic dermatitis, food allergy, allergic rhinitis, and allergen sensitisation at 1 and 2-3 years) were examined using logistic regression. Results: Human milk SCFA concentrations were broadly stable between 3 and 6 months postpartum, except for acetate which was significantly elevated at 6 months. No significant associations were observed between human milk SCFA concentrations and any allergic disease outcome after correction for multiple comparisons (all p>0.05). Conclusions: Human milk SCFA concentrations are not associated with allergic disease outcomes up to 4 years of age. These findings suggest that oral SCFA exposure via human milk is insufficient to reduce infant allergy risk, and that gut SCFA production may be a more relevant target for future allergy prevention research.

Background Growing evidence suggests that the gut microbiome influences nasal and ocular allergic inflammation through gut-mucosal immune interactions. Yet, its association with Allergic rhinitis (AR) and allergic eye symptoms (AES) remains incompletely understood in large population-based cohorts. Objective To examine associations between the gut microbiome and self-reported AR and AES in Finnish adults. Methods Shallow metagenomic sequencing was performed on stool samples from a population-based cohort (FINRISK02; n = 7,231). Microbial taxonomic and functional profiles were compared between individuals with AR (n = 1,950), AES (n = 1,554), combined allergies (AR and/or AES; n = 2,305), and controls without reported symptoms (n = 3,175). Results Allergic groups exhibited lower microbial richness and phylogenetic diversity than controls. Shared microbial and functional signatures were observed across AR and AES, consistent with their high co-occurrence (N = 1,199). Compared with controls, allergic groups showed enrichment of 17 bacterial species, predominantly from the Clostridia class, including taxa previously associated with asthma, chronic obstructive pulmonary disease, and atopic dermatitis. Allergic individuals also exhibited enrichment of pathways related to mucosal carbohydrate processing, shikimate metabolism, histidine turnover, and broader amino acid metabolism. Concurrent enrichment of histidine biosynthesis and degradation suggested altered microbial histidine metabolism. Conclusions Adult allergic symptoms are associated with gut microbiome taxonomic and functional alterations linked to mucosal barrier function and immune-related metabolism, supporting a shared gut-mucosal immune axis across allergic phenotypes.

Atopic dermatitis (AD), or eczema, is estimated to affect more than 30 million people in the United States, with over 6 million have moderate or severe disease. Chronic pruritus is a common symptom and is one of most difficult to manage. Even though itch is a major component in the pathology of AD, the biological underpinnings are not fully understood. In the present manuscript we identify a role for the neutrophil receptor, Mrgpra2, in the development of AD hyperplasia and chronic itch in the mouse. The role of Mrgprs in the context of itch have provided a huge step in our understanding of pruritus and have led to the development of novel therapeutics. Here we provide new evidence for the involvement of Mrgpra2 in the development of AD. Here we show that genetic deletion of Mrgpra2 significantly reduces scratching behaviors, transepidermal water loss, epidermal thickening, and Tslp expression in AD.

Background. Hypermobile Ehlers-Danlos syndrome (hEDS), postural orthostatic tachycardia syndrome (POTS) and mast cell activation syndrome (MCAS) are reported to co-occur frequently. It is unclear how strongly, whether symptom profiles sharpen prediction of a second diagnosis given a first, and whether the published literature can support such inference at all. Methods. We pooled 22 published cohorts-aggregate prevalence data, no primary human-subjects data-using Bayesian hierarchical random-effects models on the logit scale, and propagated the resulting posteriors through naive and tempered symptom updating. We introduce a feasibility screen derived from the Frechet-Hoeffding bounds that tests whether separately pooled marginals can describe a single population, and we characterise the identifiability of latent class structure under disease-selected sampling. Results. Directed comorbidity is strongly asymmetric: {pi}POTS|hEDS = 46.6% (95% CrI [32.5,61.5]) against {pi}hEDS|POTS = 12.1% ([3.5,38.5]), a near-fourfold gap, with {pi}MCAS|POTS lowest at 3.9% ([0.7,21.6]). Prediction intervals exceed credible intervals throughout, indicating substantial between-cohort heterogeneity. The feasibility screen finds 26 of 102 testable cells (25.5%) incompatible with any joint distribution; critically, 21 of these fail the upper Frechet bound and are invisible to the one-sided screen that is the natural first implementation. Among cells surviving the screen, symptom evidence is informative in four of six directions-P(hEDS | POTS,S) rises from 12.1% to 49.7% on a four-symptom panel under tempered updating, and P(POTS | MCAS,S) from 49.5% to 82.1%-but inert in both hEDS-cohort directions. A pathway-dispersion contrast excludes zero in two of six directions, in opposite signs and by margins of 0.1-0.2 percentage points, consistent with chance at this number of comparisons. We show latent class structure is not identified from disease-selected aggregate data, and that the single cohort reporting trivariate structure (N = 8) yields an exactly balanced table (OR = 1.00, 95% CI [0.063, 15.99]). Conclusions. The pooled directional probabilities are usable as clinical priors, with intervals wide enough to preclude precision. Symptom-conditioned prediction is supported in some directions but not those most often invoked clinically, and every estimate rests on cohorts dominated by self-reported ascertainment. The principal methodological contribution is the two-sided feasibility screen: applied here it shows that a quarter of the testable literature cannot describe one coherent population, and that a one-sided implementation understates this sixfold. Keywords: hypermobile Ehlers-Danlos syndrome; postural orthostatic tachycardia syndrome; mast cell activation syndrome; comorbidity; Bayesian meta-analysis; random-effects model; Frechet bounds; identifiability; latent class analysis; collider bias

Meibomian gland dysfunction (MGD), a disorder of the eyelid's modified sebaceous glands, is the leading cause of dry eye disease and ocular surface morbidity, yet the immune mechanisms driving gland obstruction remain poorly defined. In a cross-sectional study of 66 patients with ocular surface inflammation, we used meibography and spectral flow cytometry of tear washes to identify a disease-associated, remodeled neutrophil state whose abundance is associated with gland atrophy. Using single-cell transcriptomics in a murine model of immune-mediated MGD, we revealed a disease-associated neutrophil state that exhibited ocular surface-enrichment, CD14 and ICAM-1 expression, and elevated IFN-{gamma} response and inflammatory signatures. Spatial transcriptomics localized IFN-{gamma} signaling and neutrophil migration signatures to the periglandular compartment. The remodeled neutrophils exhibited PAD4-dependent histone citrullination, with Padi4 deletion reducing NET-associated obstructive plugging, thus identifying PAD4-dependent NETotic activity as their disease-producing output. Inhibition of IFN-{gamma} signaling phenocopied Padi4 deficiency, yet combined disruption of these pathways provided no additive protection, indicating that IFN-{gamma} and PAD4 function as separable required inputs. Remodeled neutrophils accumulated under both conditions, uncoupling disease severity from cell abundance alone. Our findings support immune-mediated obstructive MGD as a mechanistic endotype driven by the IFN-{gamma}- and PAD4-dependent effector output of a remodeled neutrophil state.

Background: Chronic obstructive pulmonary disease (COPD) is a leading cause of global morbidity and mortality, and its heterogeneity demands better biomarkers of severity and progression risk. Extracellular vesicles (EVs) are promising blood-based biomarkers, but have not been examined for COPD severity and outcomes in a large multicentre cohort. Methods: We analysed 600 COSYCONET participants (up to 54 months of follow-up). EV surface markers were profiled with the MACSPlex EV Kit IO. Cross-sectional associations with severity (GOLD, FEV1) were primary (ordinal and linear regression); longitudinal trajectories and all-cause mortality were prespecified exploratory endpoints. Results: Six EV markers showed robust associations with cross-sectional severity: CD29, CD49e and CD31 increased with severity (a cell-adhesion/matrix-remodelling signal), whereas CD81 and CD8 decreased; HLA-ABC (increasing) was less specific. No marker was linked to FEV1 decline. After FDR correction, lower levels of three markers with higher 54-month mortality (all HR<1): CD25 (HR 0.77, 95% CI 0.65-0.90, q=0.018), CD56 (HR 0.75, 95% CI 0.63-0.89, q=0.018) and CD142 (HR 0.74, 95% CI 0.60-0.90, q=0.024). CD25 and CD142 also improved reclassification, CD56 did not; a CD25 + CD69 combination showed the largest incremental signal ({Delta}C 0.017, 95% CI 0.002-0.032, p=0.027). Conclusion: Circulating EV surface markers are associated with cross-sectional COPD severity. Exploratory analyses nominate CD25, CD142 and CD25 + CD69 as candidate prognostic markers requiring external validation, suggesting minimally invasive EV profiling could complement clinical assessment in COPD.