A document by Qing-Ling Fu. Click on the document to view its contents.

Background: Food-induced immediate response of the esophagus (FIRE) is a new phenomenon that has been described in eosinophilic esophagitis (EoE) patients. It is suspected when unpleasant symptoms occur suddenly on contact of the triggering food with the esophageal surface and recur with repeated exposures. It can often be mistaken for pollen-food allergy syndrome (PFAS) and solid food dysphagia. Data on FIRE is limited to one survey study and case reports, and there are no screening studies conducted on either adults or children with EoE. In this study, we aimed to screen children aged ≥7 years old with EoE for FIRE. Methods: Demographic data were collected from medical records. A questionnaire about FIRE was applied to all participants. Skin prick tests (SPTs) were done on suspected patients to identify the triggering foods. FIRE is defined as suitable clinical symptoms with suspected food allergen exposure. Results: Seventy-eight patients (74.4% male, median age: 13.5 years) were included. Unpleasant and recurrent symptoms distinct from dysphagia with specific foods were reported in %16.7 of the patients, all of whom had concomitant allergic rhinitis (AR). The symptoms described by almost all patients were oropharyngeal itching and tingling (PFAS: 15.3%) excluding only one patient reporting retrosternal narrowing and pressure after specific food consumption (FIRE: 1.2%). Conclusions: Although definitive conclusions regarding the true prevalence of FIRE cannot be made, it does not seem to be common as PFAS. However, it deserves questioning particularly in the presence of concurrent AR and/or PFAS in children with EoE.

Tropical urban environments reveal a strong association of CD45RBloCD161+ Th2 subset to allergic rhinitis To the Editor:Allergic airway diseases such as allergic rhinitis (AR) affects more than 400 million individuals worldwide and afflicts substantial health and economic morbidity. [1] AR is strongly associated with a type 2 response, characterized by the cytokines IL-5, IL-4 and IL-13. However, the key drivers behind AR immunopathogenesis remained to be elucidated. This study aims to identify critical pathogenic cell populations associated with AR using the Singapore System Immunology Cohort (SSIC) [2] and a clinician-diagnosed paediatric cohort with active AR manifestation (Supplementary Table 1 ). In both cohorts, the eosinophilic nature of AR was confirmed by higher blood eosinophil numbers (Supplementary Figure 1 ).Whole blood gene expression analysis revealed a total of 23 probes representing 20 unique genes were associated with AR in the SSIC (Table 1A ). To account for ethnicity and environmental influences we validated our findings in BAMSE population-based cohort comprising of Swedish adolescents. Table 1B shows 11 DEGs which was also associated with AR, confirming the transferability of our findings to other populations. For the top DEGs that reached nominal significance in the SSIC we performed an Ingenuity Pathway Analysis (IPA). Supplementary Table 2 revealed important pathways related to hypersensitivity and inflammation and also functional enrichment for eosinophils, basophils and mast cells. In particular, functional activation of Th2 was highlighted as a key pathway for AR pathogenesis. As CRTH2 was reported to be expressed by cell types involved in the eosinophilic response, [3] an unsupervised cluster analysis was performed on the CRTH2+ subset in PBMC of individuals from SSIC (Figure 1 A and B ) to determine CRTH2+ subsets associated with AR. We found that CD161+Th2 subsets in particularly to be strongly associated with AR (Figure 1C and D ) (Supplementary Figure 2 ). Further characterization found that the marker CD45RB to be significantly downregulated on CD161+Th2 cells of AR individuals (Figure 1E ). Low CD45RB expression on T cells is indicative of a mature phenotype. Interestingly, significantly higher circulatory plasma IL-5 levels (Figure 1F) . Furthermore we could also demonstrate AR individuals produced significantly higher IL-5 in an in vitro PMA-stimulation assay (Figure 1G ).While we noted a small population of IL-5 secreting conventional CD161-Th2 (cTh2), IL-5 secretion was significantly elevated in CD161+Th2 cells (Figure 1H ). Strikingly, IL-5 was found to be predominantly secreted by CD45RBlo subset in both cTh2 and CD161+Th2 (Figure 1H and I ). There was also a significant increase in the IL-5 producing CD45RBloCD161+Th2 population from the AR individuals (Figure 1I ). These findings confirm CD45RBloCD161+Th2 as the main producers of IL-5.We further validated our findings in a second paediatric cohort with clinically diagnosed active AR manifestations. To further refine CD161+Th2 subset that is associated with AR, we performed unsupervised PhenoGraph and UMAP clustering on CD161+Th2 (Supplementary Figure 3A and B ). Amongst the UMAP clusters, “cluster 3” was found to be significantly associated with active AR (Supplementary Figure 3C and D ). Deep characterization reveals “cluster 3” to be an IL-5 secreting CD45RBlopopulation, confirming our earlier observation (Supplementary Figure 3E ). Furthermore, this cluster appeared to be a highly differentiated population of mature CD161+Th2 cells with an activated phenotype secreting IL-2, IL-3, IL-4, IL-9 and IL-13 concomitantly (Supplementary Figure 3E and F ). Thus, the severity of eosinophilic airway allergies such as AR seems to be driven by an activated terminally differentiated CD161+Th2 subset that is able to secrete a complex set of inflammatory cytokines.The presence of CD45RBloCD161+Th2 population in both cohorts shows the persistence and pertinence of this population in the pathogenesis of AR. Both cohorts described in this study were collected in Singapore, whereby majority of the individuals are sensitized against HDM. HDM is a perennial allergen in tropical nations such as Singapore, thus T cells in atopic individuals undergo constant stimulation. This could explain the strong association observed between CD45RB expression on CD161+Th2 cells and atopy markers despite the fact that not all subjects demonstrated active AR symptoms during the collection of SSIC cohort. Taken together, our current study unifies the markers previously reported for allergic-specific Th2 subsets and provides clarity for the pathogenic Th2 subset previously reported in different allergic diseases.[4-6] Neutralizing the CD45RBloCD161+Th2 subset should disrupt the allergic response pathway, thus providing a target for lasting therapeutic interventions. Moreover, these cells may also be leveraged as a biomarker for the effectiveness of immunotherapy as well as a potential biomarker of public health surveillance of allergic individuals.

Gut microbiota andLactobacillus species maintain the small intestine stem cell niche and ameliorate the severity of necrotizing enterocolitis Svabova Tereza1*, Jelinkova Anna1, Gautam Umesh Kumar11Laboratory of Gnotobiology, Institute of Microbiology of the Czech Academy of Sciences, 54922 Novy Hradek, Czech Republic.*corresponding author: tereza.svabova@biomed.cas.czThe microbiota plays an undisputed role in mammalian development and physiology. It enhances energy extraction from ingested food, protects against harmful pathogens, regulates immune function, and strengthens biochemical signaling. In mammals, including humans, colonization of the gut by microbes begins at birth1, and several recent studies have shown that the microbiome contributes to postnatal host development in early childhood. In this sense, microbial dysbiosis in infancy has been associated with certain diseases such as inflammatory bowel disease, cardiometabolic disorders, cancer, and neuropsychiatric disorders2.The intestinal epithelial cells are in direct contact with a large number of bacteria and the external environment, forming a barrier between inside and outside while fulfilling a critical role in the absorption of nutrients. The small intestine crypt-villus architecture is a unique structure that provides a microenvironment in which intestinal stem cells (ISCs) differentiate into a variety of different epithelial subtypes. These subtypes include enterocytes, also known as intestinal epithelial cells (IECs), Paneth cells, goblet cells, enteroendocrine cells, tuft cells, and microfold cells (M cells)3.Kim et al. demonstrated that early life gut microbiota exposure promotes the differentiation of intestinal stem cells into Paneth cells by regulating numbers of CD206+macrophages associated with epithelial Wnt signaling, which maintains mesenchymal niche cell proliferation (Figure 1). They suggested that the maintenance of this stem cell niche is critical for small intestinal homeostasis and its disruption (e.g., by antibiotic administration) can lead to inflammatory conditions, which can manifest as necrotizing enterocolitis (NEC). NEC is a severe inflammatory disease affecting the small intestine, especially in preterm infants, and is the leading cause of death in this group.To investigate the role of the microbiota and intestinal stem cell differentiation in the pathogenesis of NEC, Kim et al. induced NEC-like phenotypes in neonatal mice by exposing them to hypoxia and gavage feeding of hyperosmolar formula and LPS. ATB-induced dysbiosis resulted in further impaired stem cell niche in the small intestine and led to severe NEC manifestation. They also confirmed previous findings that microbial dysbiosis in NEC is associated with an increased abundance ofProteobacteria and a concomitant underrepresentation ofFirmicutes and Lactobacillus 4. To determine whether members of genus Lactobacillus affect Paneth cell formation during NEC onset, Kim et al. treated pregnant females and their pups with selected Lacticaseibacillus rhamnosus (Lr) strain in the presence or absence of NEC experimental conditions. They found that Lr transplantation corrected the impaired development of the mesenchymal niche and Paneth cell differentiation and consequently partially rescued the NEC-like phenotypes (Figure 1)4.Previous studies in germ-free mice and mice with Toll-like receptor knockout have highlighted the key relationship between the microbiome and NEC development5. Probiotic administration has been suggested as a potential strategy to prevent NEC. In general, probiotic bacteria, including Lactobacillus species, modulate microbiota composition, intestinal epithelial barrier function, and cytokine secretion. Kim et al. showed that transplantation of Lr restored the amount of Lactobacilli resulting in an improvement of NEC-like phenotypes. We have recently shown that administration ofLactiplantibacillus plantarum WJL also increased the proliferation of intestinal epithelial stem cells in chronically undernourished juvenile mice, resulting in improved growth of the young. This effect was strictly bacterial strain-dependent, and NOD2 signaling in intestinal epithelial cells was essential for the bacteria-mediated beneficial effect6. A growing body of evidence suggests that the strain specificity of probiotic microbes and their efficacy in alleviating specific diseases are crucial aspects that are often overlooked when selecting the best probiotic microbes7. Therefore, it would be important to determine whether all probiotic bacterial species or even different Lr strains promote the stem cell niche development by the same mechanism. Further, as it has been shown that NOD2 signaling plays a crucial role in epithelial stem cell proliferation, the role of this receptor in the NEC prevention and development should be probed.To sum up, the study by Kim et al. provides another important contribution to the understanding of the mechanism of NEC pathogenesis. However, more research is needed to fully understand the role ofLactobacilli and other probiotic bacteria in the prevention of NEC and to strengthen their potential as therapeutic agents to combat this serious disease.

Sequential proteomic profiling of patients with Stevens Johnson-Syndrome or Toxic Epidermal NecrolysisEmmanuel Contassot (PhD) 1, 2, Brüggen Marie-Charlotte (MD, PhD) 3, 4, 51 Dermatology Department, University Hospital of Basel, Basel, Switzerland2 Department of Biomedicine, University of Basel, Basel, Switzerland3 Department of Dermatology, University Hospital Zurich, Zurich, Switzerland4 Christine Kühne Center for Allergy Research and Education CK-CARE, Davos, Switzerland5 Faculty of Medicine, University of Zurich, Zurich, Switzerland

IL-17 has emerged as an important cytokine in protecting the host from mucosal infections, but also as a pathogenic determinant and therapeutic target in numerous autoimmune and inflammatory diseases (e.g. psoriasis, psoriatic arthritis and ankylosing spondylitis, inflammatory bowel disease and multiple sclerosis) [(1)](#ref-0001). The IL-17 family includes six members (IL-17A to IL-17F) that act through the IL-17 receptors [(1)](#ref-0001). The most studied IL-17A, as well as IL-17F, binds to IL-17RA and IL-17RC resulting in heterodimerization. Currently IL-17A, IL-17F, IL-17RA or IL-23, a cytokine produced by innate immune cells that promotes expansion of Th17 cell populations, are targetable by monoclonal antibodies (mAbs). These mAbs have been approved for the treatment of different autoimmune diseases, most notably psoriasis, where their efficacy has outperformed conventional non-steroidal anti-inflammatory and tumor necrosis factor (TNF) blocking drugs. However, clinical trials and real-life experience have shown an increase in fungal and bacterial upper respiratory tract infections in patients treated with mAbs that block IL-23/IL-17 signaling. Accordingly, single nucleotide polymorphisms in genes encoding IL-17A, IL-17RA, IL-17RC, IL-23, or NF-κB activator 1 (ACT1, an adapter protein downstream of the IL-17R) which abrogate cellular responsiveness to IL-17A, were associated with susceptibility to chronic mucocutaneous candidiasis (CMC), a persistent infection of the skin, nails, and/or mucous membranes with commensal Candida species [(2)](#ref-0002). So new effective targeted approaches in IL-17 signaling are desirable. Knizkova and colleagues identified a new adaptor molecule involved in the IL-17/IL-17R cascade [(3)](#ref-0003). Through murine and human cell models, the authors found that CMTM4 (CKLF Like MARVEL Transmembrane Domain Containing 4) constitutively bound to the subunit IL-17RC becoming integral part of the IL-17R signaling complex (IL-17RSC) upon IL-17A stimulation. CMTM4 promoted the surface expression of IL-17RC by regulating posttranslational modifications, especially IL-17RC glycosylation and trafficking to trans-Golgi up to plasma membrane. CMTM4 was required for the recruitment of adapter ACT1, for the activation of p38, JNK and transcription of genes encoding proinflammatory cytokines upon IL-17A stimulation (Figure 1A). Keratinocytes from the tail of Cmtm4−/− mice specifically express lower levels of IL-17RC respect to Cmtm4+/+ mice (Figure 1B). In vivo, when imiquimod (IMQ) was applied on the ears or shaven backs of Cmtm4−/− mice, they developed less severe psoriatic lesions and lower local expression of IL-17A target genes compared to Cmtm4+/+ mice (Figure 1C).

The field of medicine is witnessing an exponential growth of interest in Artificial Intelligence (AI), which enables new research questions and the analysis of larger and new types of data. Nevertheless, applications that go beyond proof of concepts and deliver clinical value remain rare, especially in the field of allergy and immunology. This narrative review provides a fundamental understanding of the core concepts of AI and critically discusses its limitations and open challenges, such as data availability and bias, along with potential directions to surmount them. We provide a conceptual framework to structure AI applications within this field and discuss forefront case examples. Most of these applications of AI and machine learning in allergy concern supervised learning and unsupervised clustering, with a strong emphasis on diagnosis and subtyping. A perspective is shared on guidelines for good AI practice to guide readers in applying it effectively and safely, along with prospects of field advancement and initiatives to increase clinical impact. We anticipate that AI can further deepen our knowledge of disease mechanisms and contribute to precision medicine in allergy.

Insect venom allergy is the most frequent cause of anaphylaxis in Europe and possibly worldwide. The majority of systemic allergic reactions after insect stings are caused by Hymenoptera and among these, vespid genera induce most of the systemic sting reactions (SSR). Honey bees are the second leading cause of SSR. Depending on the global region, other Hymenoptera such as different ant genera are responsible for SSR. Widely distributed hornets and bumblebees or local vespid or bee genera rarely induce SSR. Hematophagous insects such as mosquitoes and horse flies usually cause (large) local reactions while SSR occasionally occur. This position paper aims to identify either rare or locally important insects causing SSR as well as rarely occurring SSR after stings or bites of widely distributed insects. We summarized relevant venom or saliva allergens and intended to identify possible cross-reactivities between the insect allergens. Moreover, we aimed to locate diagnostic tests for research and routine diagnosis, which are sometimes only regionally available. Finally, we gathered information on disposable immunotherapies. Major allergens of most insects were identified, and cross-reactivity between insects was frequently observed. While some diagnostics and immunotherapies are locally available, standardized skin tests and immunotherapies are generally lacking in rare insect allergy.

Autoimmunity is the break of tolerance to self-antigens that leads to organ-specific or systemic diseases characterized by the presence of pathogenic autoreactive antibodies (AAb) produced by plasmablast and/or plasma cells. AAb are prevalent in the general population and not systematically associated with clinical symptoms. In contrast, in some individuals, these AAb are pathogenic and drive the development of signs and symptoms of antibody-mediated autoimmune diseases (AbAID). AAb production, isotype profiles, and glycosylations are promoted by pro-inflammatory triggers linked to genetic, environmental, and hormonal parameters. Recent evidence supports a role for pathogenic AAb of the IgE isotype in a number of AbAID. Autoreactive IgE can drive the activation of mast cells, basophils and other types of FcεRI-bearing cells and may play a role in promoting autoantibody production and other pro-inflammatory pathways. In this review, we discuss the current knowledge on the pathogenicity of autoreactive IgE in AbAID and their status as therapeutic targets. We also highlight unresolved issues including the need for assays that reproducibly quantify IgE AAbs, to validate their diagnostic and prognostic value, and to further study their pathophysiological contributions to AbAID.

CLA + memory T cells constitute a small subset of human memory T cells. Circulating skin-homing T cells participate in several aspects of atopic dermatitis, such as Staphylococcus aureus involvement in inflammation, the abnormal Th2 immune response, biomarkers, clinical aspects of the patients, pruritus, and the mechanism of action of targeted therapies. Superantigens, IL-13, IL-31, pruritus, CCL17 and early effects on dupilumab-treated patients have in common that they are related to CLA + T cell response in patients. The function of CLA + T cells is closely related to the role of T cells belonging to the skin-associated lymphoid tissue and could be a reason why they reflect different mechanisms of atopic dermatitis. The goal of this review is to gather all this translational information of atopic dermatitis pathology.

Journal: Allergy

While both the incidence and general awareness of food allergies is increasing, the variety and clinical availability of therapeutics remain limited. Therefore, investigations into the potential factors contributing to the development of food allergy and the mechanisms of natural tolerance or induced desensitization are required. In addition, a detailed understanding of the pathophysiology of food allergies is needed to generate compelling, enduring, and safe treatment options. New findings regarding the contribution of barrier function, the effect of emollient interventions, mechanisms of allergen recognition, and the contributions of specific immune cell subsets through rodent models and human clinical studies provide novel insights. With the first approved treatment for peanut allergy, the clinical management of food allergy is evolving towards less intensive, alternative approaches involving fixed doses, lower maintenance dose targets, co-administration of biologicals, adjuvants, and tolerance-inducing formulations. The ultimate goal is to improve immunotherapy and develop precision-based medicine via risk phenotyping allowing optimal treatment for each food-allergic patient.

Meglumine gadoterate induces immunoglobulin-independent human mast cell activation and MRGPRX2 internalizationTo the Editor,Gadolinium-based contrast agents (GBCA) are intravenous drugs used to enhance resolution in magnetic resonance imaging. They can induce immediate hypersensitivity reactions, yet their pathogenic mechanisms remain poorly characterized. This hampers the ability to predict which patients are at risk of developing them.1 In fact, affected patients usually show negative skin-tests and can react upon the first known GBCA exposure, which implies that IgE-independent mechanisms might be driving this inflammatory response.The Mas-related G protein-coupled receptor member X2 (MRGPRX2) has been recently associated with non-IgE mediated immediate hypersensitivity reactions.2 Some drugs, such as fluoroquinolones, vancomycin, neuromuscular blockade agents, icatibant, morphine, leuprolide and iodinated contrast media, have been reported to activate MRGPRX2, which is highly expressed in mast cells (MCs).3To assess the ability of GBCA to induce non-IgE-mediated hypersensitivity reactions, we stimulated the human MC line LAD2 with several commercial GBCA, namely, meglumine gadoterate, gadobutrol, gadoxetate disodium and gadoteridol. Then, we determined cell viability and degranulation by flow cytometry4 (see a detailed material and methods section in this article´s online supplementary ).Of the GBCA tested, only meglumine gadoterate was able to induce significant MC activation (Figure 1A ) without compromising cell viability (Figure 1B ), as compared to unstimulated MCs. We further assessed MRGPRX2 expression on LAD2 cells by flow cytometry, as well as changes in its expression following stimulations with either meglumine gadoterate or vancomycin (a known agonist of MRGPRX2).5 Under basal conditions, LAD2 cells expressed high levels of MRGPRX2 (Figure 1C ). Following incubation with vancomycin, the level of MRGPRX2 expression was reduced, as compared to untreated LAD2 cells. Interestingly, we observed a similar decrease in MRGPRX2 expression levels upon meglumine gadoterate and vancomycin challenges, as compared to controls, suggesting both the signaling and the internalization of this receptor (Figure 1D ).Meglumine gadoterate is an ionic macrocyclic paramagnetic contrast media. It is composed by gadolinium, which together with the chelating agent tetraxetan (also known as DOTA), yields gadoteric acid. The base meglumine and gadoteric acid form the salt meglumine gadoterate (Figure 2A ). Given that MRGPRX2 has affinity for cationic amphiphilic compounds,6 we ascertained the ability of meglumine to induce MC activation. Meglumine itself induced MC degranulation without affecting cell viability, as compared to untreated cells (Figure 2B ), although a reduction in MRGPX2 expression could not be confirmed (data not shown). Interestingly, meglumine caused MC activation at lower concentrations than meglumine gadoterate, according to the half maximal effective concentration (EC50) of both substances (Figure 2C ). The logarithmically transformed EC50 for meglumine gadoterate was 2.04 (R2= 0.75), and for meglumine was about one order of magnitude lower (1.06; R2= 0.71). Considering the EC50 for meglumine and its proportion in meglumine gadoterate (~26%), meglumine could be its main component responsible for MC degranulation.In conclusion, our study demonstrates the ability of meglumine gadoterate to induce MC activation, by an immunoglobulin-independent mechanism that is likely mediated by MRGPRX2. Furthermore, we have delved into the meglumine gadoterate components that are involved in MC activation, and identified meglumine as a potential causative of non-IgE mediated hypersensitivity reactions. These data raise the possibility that immediate hypersensitivity reactions following intravascular administration of ionic iodinated contrast media may be at least partly mediated by meglumine. Further studies should be performed to define clinically relevant interactions between diverse radiological contrast media and MRGPRX2.Authors: Paula H. Ruiz de Azcárate,1#Rodrigo Jiménez-Saiz,1-4 #* Celia López-Sanz,1 Azahara López-Raigada,5Francisco Vega,5 Carlos Blanco,5*# First authors* Corresponding authorsAffiliations: 1Department of Immunology, Instituto de Investigación Sanitaria Hospital Universitario de La Princesa (IIS-Princesa), Universidad Autónoma de Madrid (UAM), Madrid, Spain.2Department of Immunology and Oncology, Centro Nacional de Biotecnología (CNB)-CSIC, Madrid, Spain.3Faculty of Experimental Sciences, Universidad Francisco de Vitoria (UFV), Madrid, Spain.4Department of Medicine, McMaster Immunology Research Centre (MIRC), Schroeder Allergy and Immunology Research Institute (SAIRI), McMaster University, Hamilton, ON, Canada.5Department of Allergy, Instituto de Investigación Sanitaria Hospital Universitario de La Princesa (IIS-Princesa), Universidad Autónoma de Madrid (UAM), Madrid, Spain.*Co-correspondence to :1) Rodrigo Jiménez-Saiz, Department of Immunology, Instituto de Investigación Sanitaria Hospital Universitario de La Princesa (IIS-Princesa), Diego de León 62, 28006, Madrid, Spain. Email address: rodrigo.jimenez@ufv.es2) Carlos Blanco, Department of Allergy, Instituto de Investigación Sanitaria Hospital Universitario de La Princesa (IIS-Princesa), Diego de León 62, 28006, Madrid, Spain. Email address: cblague@gmail.com Funding information: RJS reports grants by the FSE/FEDER through the Instituto de Salud Carlos III (CP20/00043; PI22/00236; Spain), The Nutricia Research Foundation (NRF-2021-13; The Netherlands), New Frontiers in Research Fund (NFRFE-2019-00083; Canada) and SEAIC (BECA20A9; Spain). PHR is supported by the INVESTIGO Program of the Community of Madrid (Spain), which is funded by “Plan de Recuperación, Transformación y Resiliencia” and “NextGenerationEU” of the European Union (09-PIN1-00015.6/2022).Conflict of interest : All the authors have no significant conflicts of interest to declare in relation to this manuscript.References1. Vega F, Lopez-Raigada A, Mugica MV, Blanco C. Fast challenge tests with gadolinium-based contrast agents to search for an alternative contrast media in allergic patients. Allergy.2022;77(10):3151-3153.2. Kolkhir P, Ali H, Babina M, et al. MRGPRX2 in drug allergy: What we know and what we do not know. J Allergy Clin Immunol. 2022.3. Foer D, Wien M, Karlson EW, Song W, Boyce JA, Brennan PJ. Patient Characteristics Associated With Reactions to Mrgprx2-Activating Drugs in an Electronic Health Record-Linked Biobank. J Allergy Clin Immunol Pract. 2022.4. López-Sanz C, Sánchez-Martínez E, Jiménez-Saiz R. Protocol to desensitize human and murine mast cells after polyclonal IgE sensitization. STAR Protocols. 2022;3(4):101755.5. Navines-Ferrer A, Serrano-Candelas E, Lafuente A, Munoz-Cano R, Martin M, Gastaminza G. MRGPRX2-mediated mast cell response to drugs used in perioperative procedures and anaesthesia. Sci Rep.2018;8(1):11628.6. Wolf K, Kühn H, Boehm F, et al. A group of cationic amphiphilic drugs activates MRGPRX2 and induces scratching behavior in mice. J Allergy Clin Immunol. 2021;148(2):506-522.e508.

Title : Distinct and mutually exclusive Ca++ flux- and adenyl cyclase-inducing gene expression profiles of G-Protein-Coupled Receptors on human antigen-specific B cellsAuthors : Iris Chang1,2†, Abhinav Kaushik, PhD1,2†, Pattraporn Satitsuksanoa PhD1, Minglin Yang1, Laura Buergi Msc1, Stephan R. Schneider Msc1, Cezmi A. Akdis, MD1, Kari Nadeau MD, PhD2, Willem van de Veen, PhD1, Mübeccel Akdis, MD, PhD1*1 Swiss Institute of Allergy and Asthma Research (SIAF), University of Zürich, Davos, Switzerland.2 Sean N. Parker Center for Allergy and Asthma Research, Department of Medicine, Stanford University, Palo Alto, CA, USA.† Contributed equally* Corresponding authorB cells play an essential role in allergies by producing allergen-specific IgE, which is a prerequisite for allergen-induced degranulation of mast cells (MCs) and basophils. MCs, basophils, dendritic cells and bacteria are capable of releasing inflammatory mediators including histamine. Histamine is a bioactive amine that exerts its function through binding to histamine receptors (HRs), which are 7-transmembrane G-protein-coupled receptors (GPCRs). There are four types of HRs (HR1-4), wherein HR1 ligation triggers Ca2+ mobilization, HR2 stimulates and increases cAMP concentrations, and HR3 and HR4 inhibit cAMP accumulation1. In the presence of histamine in the environment, high affinity HR1is triggered causing cellular activation, followed by expression of 10 times lower affinity HR2 to regulate the over-inflammatory events. These HRs trigger different intracellular events upon activation, with HR1 as a Ca2+ flux-inducing activating receptor and HR2 as an adenyl cyclase-stimulating suppressive receptor 1,2. Therefore, to explore the response of B-cells in allergic diseases, we analyzed the expression profile of HRs and other GPCRs in B cell clones. We hypothesized that the expression profile of HRs (HR1+ vs HR2+ B cell clones) is associated with significant changes in the expression profile of other GPCRs that govern the downstream cascade of pathways associated with cAMP signaling or Ca2+ mobilization.A total of 27 IgG1 and IgG4 expressing B cell clones were isolated for gene expression analysis under BCR stimulated and unstimulated conditions (Figure 1A and Online Supplementary Methods) . Interestingly, we observed B-cell clones with mutually exclusive expression profile of HRH1 and HRH2 genes (Figure 1B), with more HRH1+ B-cell clones in BCR-stimulated samples than unstimulated samples. The subsequentHRH1+ vs HRH2+ differential gene expression analysis (Figure 1C ), reveal 27 differentially expressed (DE) GPCRs in unstimulated samples, with up-regulated P2RY13  and C5AR1genes  in HRH2 + B-cell clones (Figure 2A) , which are associated with the cAMP signaling and suppressive pathway3,4. To further prioritize the DE GPCRs specifically associated with Ca2+ and cAMP signaling pathways, we reconstructed the co-expression networks and performed the weighted degree analysis across HRH1+ vs HRH2+ clones. The analysis reveals that the purinergic receptor family of GPCRs (i.e. P2RY1 , P2RY13 )  and complement component 5a receptor family of genes (i.e. C5AR1  and C5AR2 ) share highest degree of interactions. These genes are up-regulated inHRH2+ samples and are well-known to affect cAMP signaling pathway3,4 (Figure S1A ). Intriguingly, we also observed upregulation of GPR35  in HRH2 + B cells, which is associated in maintaining a low baseline Ca2+ level5. Similarly, we also observed up-regulation of GPR68 and GPR171 in HRH1 + B cells; both are known to stimulate Ca2+ flux (Online Supplementary Discussion) .Similarly, 28 GPCRs were differentially expressed in BCR-stimulated samples (Figure 2B ), including higher expression of serotonin receptor type 1A (HTR1A ) and HCAR1  (or GPR81 ) inHRH2+ samples, with a cAMP-linked suppressive function. In addition, we also observed upregulation of complement component 5a receptor family of genes (i.e., C5AR1  and C5AR2 ) and GPR35 , in agreement with the trend observed in unstimulatedHRH2 + B-cell clones. Surprisingly, we observed a higher expression of prostaglandin E2 receptor subtype EP4 (PTGER4)  and adenosine A2A receptor (ADORA2A ) in HRH2+ samples3,6, which are known to be associated with activation of cAMP production and share the highest strength of interactions with the cAMP signaling sub-network (Figure S1B ). Among the up-regulated genes in HRH1 + samples, we found three Ca2+ mobilizing genes, i.e., GPR34 ,P2RY10  and PTAFR .The results reported in this study provides data for a novel hypothesis suggesting investigation of co-expressed genes that may play important synergistic or antagonistic regulatory roles in B-cell function.

Germinal centers (GC) are the sites of B cell clonal expansion, somatic hypermutation and clonal selection, a process that leads to the production of antibodies of higher affinity [1](#ref-0001). Efforts have been made to understand the kinetic of events controlling the GC and the production of specific antibodies in protective as well in pathogenic responses, such as autoimmunity and allergy. The ability of newly mutated GC clones to capture and present antigen to T follicular helper cells (Tfh) in the light zone of the GC is crucial for clonal survival and selection. Tfh cells produce IL-21, a key cytokine for the GC reaction and antibody responses [2](#ref-0002). However, it was not understood how IL-21 acts independently on T and B cells to mediate the GC reaction. In this study Quast and colleagues [3](#ref-0003) contribute to elucidate the specific role of IL-21 on the GC reaction and how IL-21 bioavailability affects the outcome of the GC response. They demonstrate that IL-21 influences Tfh cell differentiation and expansion early, before the GC establishment, as well later during GC development, through both autocrine and paracrine mechanisms, regardless of cognate T-B cell interactions.

A document by Carmen H. Li. Click on the document to view its contents.

Direct cleavage and activation of gasdermin B by asthma trigger allergensTo the Editor:Recent fine-mapping studies have pointed to gasdermn B (GSDMB ) as a potential asthma susceptibility gene in 17q21 locus, the strongest and most highly replicated signal in genome-wide association studies1. The GSDMB protein is a member of the gasdermin family that, when cleaved, triggers an inflammatory cell death known as pyroptosis2. Caspase-1 and granzyme A have been shown to cut GSDMB at specific sites to release the N-terminal fragment of the protein (GSDMB-NT) that has the ability to induce pyroptosis in cells, including airway epithelial cells3,4. These findings suggest that the role of GSDMB in asthma lies in its ability to be activated through cleavage to induce pyroptosis; however, it remains unclear whether GSDMB cleavage and activation occur in the context of asthma.Common asthma trigger allergens often possess protease activities that cause airway epithelial injury and inflammation5,6. We thus tested whether the allergens directly cleave GSDMB. Incubation of extracts from house dust mite (HDM), a common asthma trigger, with lysates from human bronchial epithelial cells, which express endogenous GSDMB3, resulted in GSDMB cleavage as evidenced by the appearance of a smaller protein around 17kD (Figure 1A). Since the GSDMB antibody used in the Western blotting targets the C-terminus of the protein, the 17kD protein band likely represents the C-terminal GSDMB fragment. Such GSDMB cleavage was also observed when lysates from cells expressing C-terminal-FLAG-tagged GSDMB were mixed with HDM extract (Figure 1B). Furthermore, mold or cockroach extract also cleaved tagged GSDMB (Figure 1C). The cleavage of GSDMB protein by all allergen extracts resulted in a single product of similar size (about 17 kD), suggesting a specific cutting site.To identify the cleavage site, we incubated recombinant full-length GSDMB with HDM extract and resolved the cleaved protein products on SDS-PAGE (Figure 1D). We excised the putative 17 kD C-terminal fragment (GSDMB-CT, Figure 1D) and determined the N-terminal amino acid sequence of the fragment via Edman sequencing (Supplemental Figure S1, Figure 1E). Despite some ambiguities, the first ten amino acid residues of the 17 kD GSDMB-CT largely map to position 245 to 254 (SLGSEDSRNM) of the full length GSDMB protein (Figure 1E). This result indicates that GSDMB was cleaved immediately after the lysine residue at position 244 (K244). Interestingly, granzyme A also cuts GSDMB at the same K244 site4. To confirm K244 as the site of cleavage, we mutated lysine 244 to alanine (K244A) in GSDMB and tested whether the mutant protein can be cleaved by HDM. As shown by Western blotting, HDM was able to cleave wild type (WT) GSDMB but failed to cleave K244A GSDMB as evidenced by the absence of the 17 kD fragment (Figure 1F).The cleavage of GSDMB by HDM is expected to release an N-terminal fragment of 244 amino acids (GSDMB-NT-K244) (Figure 2A). We next tested whether GSDMB-NT-K244 triggers pyroptosis. Transfection of GSDMB-NT-K244 induced cell morphological changes characteristic of pyroptosis, including rounding up and detachment (Figure 2B). LDH release assay confirmed increased toxicity in these cells (~3.4 fold) as compared to cells transfected with the full-length GSDMB (Figure 2C). Consistent with our previous finding on GSDMB-NT shortened by a functional asthma-associated splice variant3, transfection of a truncated GSDMB-NT from the variant (NT-K231var) did not induce pyroptosis (Figure 2B,C).While future studies are needed to identify the specific proteases within the allergen extracts that cleave GSDMB, our current study demonstrates that asthma triggers such as HDM can directly cleave and activate GSDMB, thus providing biochemical evidence linking GSDMB-mediated pyroptosis to asthma.

Background: Pruritus has been reported as an adverse drug reaction to arsenic trioxide, but the association of arsenic exposure with pruritus has not been systematically investigated. To investigate the association of arsenic exposure with pruritus, we performed observational, interventional, and Mendelian randomization studies. Methods: A cross-sectional study was conducted in Shimen, China. A Mendelian randomization study was conducted to confirm the causal relationship between susceptibility to arsenic toxicity, in terms of genetically predicted percentages of monomethylated arsenic (MMA%) and dimethylated arsenic (DMA%) in urine, and chronic pruritus in the UK Biobank participants. Then, a case-control study in Shimen participants was conducted to determine the biomarker for pruritus, and arsenite-treated mice were used to confirm the biomarker. Last, a randomized, double-blind, placebo-controlled trial was conducted to test the efficacy of naloxone, a μ-opioid receptor antagonist, in arsenic-exposed patients with pruritus in Shimen. Results: Hair arsenic showed a dose-response relationship with the intensity of itch in 1092 participants. The Mendelian randomization analysis confirmed the causal relationship in the UK Biobank participants, with odds ratios of 1.043 for MMA% and 0.904 for DMA% above versus under median. Serum β-endorphin was identified as a significant biomarker associated with the intensity of itch. Consistently, treatment with arsenite in mice upregulated the level of β-endorphin. The randomized controlled trial showed that treatment with sublingual naloxone significantly relieved the intensity of itch in arsenic-exposed participants. Conclusion: Arsenic exposure is associated with pruritus, and β-endorphin serves as a biomarker of pruritus. Naloxone relieves pruritus in patients with [arseniasis](javascript:;).