Mapping the adult human esophagus in vivo and in vitro.

Many esophageal diseases can arise during development or throughout life. Therefore, well-characterized in vitro models and detailed methods are essential for studying human esophageal development, homeostasis and disease. Here, we (1) create an atlas of the cell types observed in the normal adult human esophagus; (2) establish an ancestrally diverse biobank of in vitro esophagus tissue to interrogate homeostasis and injury; and (3) benchmark in vitro models using the adult human esophagus atlas. We created a single-cell RNA sequencing reference atlas using fresh adult esophagus biopsies and a continuously expanding biobank of patient-derived in vitro cultures (n=55 lines). We identify and validate several transcriptionally distinct cell classes in the native human adult esophagus, with four populations belonging to the epithelial layer, including basal, epibasal, early differentiating and terminally differentiated luminal cells. Benchmarking in vitro esophagus cultures to the in vivo reference using single-cell RNA sequencing shows that the basal stem cells are robustly maintained in vitro, and the diversity of epithelial cell types in culture is dependent on cell density. We also demonstrate that cultures can be grown in 2D or as 3D organoids, and these methods can be employed for modeling the complete epithelial layers, thereby enabling in vitro modeling of the human adult esophagus.

IL-4-STAT6 axis amplifies histamine-induced vascular endothelial dysfunction and hypovolemic shock.

BACKGROUND: Mast cell-derived mediators induce vasodilatation and fluid extravasation, leading to cardiovascular failure in severe anaphylaxis. We previously revealed a synergistic interaction between the cytokine IL-4 and the mast cell-derived mediator histamine in modulating vascular endothelial (VE) dysfunction and severe anaphylaxis. The mechanism by which IL-4 exacerbates histamine-induced VE dysfunction and severe anaphylaxis is unknown. OBJECTIVE: We sought to identify the IL-4-induced molecular processes regulating the amplification of histamine-induced VE barrier dysfunction and the severity of IgE-mediated anaphylactic reactions. METHODS: RNA sequencing, Western blot, Ca2+ imaging, and barrier functional analyses were performed on the VE cell line (EA.hy926). Pharmacologic degraders (selective proteolysis-targeting chimera) and genetic (lentiviral short hairpin RNA) inhibitors were used to determine the roles of signal transducer and activator of transcription 3 (STAT3) and STAT6 in conjunction with in vivo model systems of histamine-induced hypovolemic shock. RESULTS: IL-4 enhancement of histamine-induced VE barrier dysfunction was associated with increased VE-cadherin degradation, intracellular calcium flux, and phosphorylated Src levels and required transcription and de novo protein synthesis. RNA sequencing analyses of IL-4-stimulated VE cells identified dysregulation of genes involved in cell proliferation, cell development, and cell growth, and transcription factor motif analyses revealed a significant enrichment of differential expressed genes with putative STAT3 and STAT6 motif. IL-4 stimulation in EA.hy926 cells induced both serine residue 727 and tyrosine residue 705 phosphorylation of STAT3. Genetic and pharmacologic ablation of VE STAT3 activity revealed a role for STAT3 in basal VE barrier function; however, IL-4 enhancement and histamine-induced VE barrier dysfunction was predominantly STAT3 independent. In contrast, IL-4 enhancement and histamine-induced VE barrier dysfunction was STAT6 dependent. Consistent with this finding, pharmacologic knockdown of STAT6 abrogated IL-4-mediated amplification of histamine-induced hypovolemia. CONCLUSIONS: These studies unveil a novel role of the IL-4/STAT6 signaling axis in the priming of VE cells predisposing to exacerbation of histamine-induced anaphylaxis.

Induction of Interleukin-9-Producing Mucosal Mast Cells Promotes Susceptibility to IgE-Mediated Experimental Food Allergy.

Experimental IgE-mediated food allergy depends on intestinal anaphylaxis driven by interleukin-9 (IL-9). However, the primary cellular source of IL-9 and the mechanisms underlying the susceptibility to food-induced intestinal anaphylaxis remain unclear. Herein, we have reported the identification of multifunctional IL-9-producing mucosal mast cells (MMC9s) that can secrete prodigious amounts of IL-9 and IL-13 in response to IL-33, and mast cell protease-1 (MCPt-1) in response to antigen and IgE complex crosslinking, respectively. Repeated intragastric antigen challenge induced MMC9 development that required T cells, IL-4, and STAT6 transcription factor, but not IL-9 signals. Mice ablated of MMC9 induction failed to develop intestinal mastocytosis, which resulted in decreased food allergy symptoms that could be restored by adoptively transferred MMC9s. Finally, atopic patients that developed food allergy displayed increased intestinal expression of Il9- and MC-specific transcripts. Thus, the induction of MMC9s is a pivotal step to acquire the susceptibility to IgE-mediated food allergy.

IL-4 receptor alpha signaling alters oral food challenge and immunotherapy outcomes in mice.

BACKGROUND: Food allergy diagnosis and management causes a number of social and emotional challenges for individuals with food allergies and their caregivers. This has led to increased interest in developing approaches to accurately predict food allergy diagnosis, severity of food allergic reactions, and treatment outcomes. However, the utility of these approaches is somewhat conflicting. OBJECTIVE: We sought to develop and utilize a murine model that mimics the disease course of food allergy diagnosis and treatment in humans and to identify biomarkers that predict reactivity during food challenge (FC) and responsiveness during oral immunotherapy (OIT) and how these outcomes are modified by genetics. METHODS: Skin-sensitized intestinal IL-9 transgenic (IL9Tg) and IL9Tg mice backcrossed onto the IL-4RαY709F background received a single intragastric exposure of egg antigen (ovalbumin), underwent oral FC and OIT; food allergy severity, mast cell activation, and ovalbumin-specific IgE levels were examined to determine the predictability of these outcomes in determining reactivity and treatment outcomes. RESULTS: Subcutaneous sensitization and a single intragastric allergen challenge of egg antigen to BALB/c IL9Tg mice and Il4raY709F IL9Tg induced a food allergic reaction. Enhanced IL-4Rα signaling altered the symptoms induced by the first oral exposure, decreased the cumulative antigen dose, increased the severity of reaction during oral FC, and altered the frequency of adverse events and OIT outcomes. Biomarkers after first oral exposure indicated that only the severity of the initial reaction significantly correlated with cumulative dose of oral FC. CONCLUSION: Collectively, these data indicate that single nucleotide polymorphisms in IL-4Rα can alter clinical symptoms of food allergic reactions, severity, and reactive dose during FC and OIT, and that severity of first reaction can predict the likelihood of reaction during FC in mice with IL-4Rα gain of function.

Mucosal IgA immune complex induces immunomodulatory responses in allergic airway and intestinal TH2 disease.

BACKGROUND: IgA is the most abundant immunoglobulin at the mucosal surface and although its role in regulating mucosal immunity is not fully understood, its presence is associated with protection from developing allergic disease. OBJECTIVE: We sought to determine the role of IgA immune complexes for therapeutic application to mucosal allergic responses. METHODS: Trinitrophenol (TNP)-specific IgA immune complexes were applied, using TNP-coupled ovalbumin (OVA), to airway and gut mucosal surfaces in systemically sensitized allergic animals to regulate allergen challenge responses. Animals were assessed for both pathologic and immune-mediated responses in the lung and gut, respectively, using established mouse models. RESULTS: The mucosal application of IgA immune complexes in the lung and gut with TNP-OVA regulated TH2-driven allergic response in the lung and gut, reducing TH2 cytokines and mucus (lung) as well as diarrhea and temperature loss (gut), but increasing IL-10 and the number of regulatory T cells. The IgA-OVA immune complex did not alter peanut-induced anaphylaxis, indicating antigen specificity. Using OVA-specific DO.11-green fluorescent protein IL-4 reporter mouse-derived TH2-skewed cells in a transfer model demonstrated that mucosal IgA immune complex treatment reduced TH2-cell expansion and increased the number of regulatory T cells. To address a potential mechanism of action, TGF-ß and IL-10 were induced in bone marrow-derived dendritic cells when they were exposed to IgA immune complex, suggesting a regulatory phenotype induced in dendritic cells that also led to an altered primary T-cell-mediated response in in vitro OVA-specific assays. CONCLUSIONS: These studies highlight one possible mechanism of how allergen-specific IgA may provide a regulatory signal to reduce the development of allergic responses in the lung and gut.

IL-13-induced STAT3-dependent signaling networks regulate esophageal epithelial proliferation in eosinophilic esophagitis.

BACKGROUND: Basal zone hyperplasia (BZH) and dilated intercellular spaces (DISs) are thought to contribute to the clinical manifestations of eosinophilic esophagitis (EoE); however, the molecular pathways that drive BZH remain largely unexplored. OBJECTIVE: We sought to define the role of IL-13-induced transcriptional programs in esophageal epithelial proliferation in EoE. METHODS: We performed RNA sequencing, bioinformatics, Western blot, reverse transcriptase quantitative PCR, and histologic analyses on esophageal biopsies from healthy control and patients with EoE, primary esophageal cells derived from patients with EoE, and IL-13-stimulated esophageal epithelial keratinocytes grown at the air-liquid interface (EPC2-ALI). Genetic (shRNA) and pharmacologic (proteolysis-targeting chimera degrader) approaches and in vivo model of IL-13-induced esophageal epithelial remodeling (Krt5-rtTA x tetO-IL-13Tg) were used to define the role of signal transducer and activator of transcription 3 (STAT3) and STAT6 and secreted frizzled-related protein 1 (SFRP1) in esophageal epithelial proliferation. RESULTS: RNA-sequencing analysis of esophageal biopsies (healthy control vs EoE) and EPC2-ALI revealed 82 common differentially expressed genes that were enriched for putative STAT3 target genes. In vitro and in vivo analyses revealed a link between IL-13-induced STAT3 and STAT6 phosphorylation, SFRP1 mRNA expression, and esophageal epithelial proliferation. In vitro studies showed that IL-13-induced esophageal epithelial proliferation was STAT3-dependent and regulated by the STAT3 target SFRP1. SFRP1 mRNA is increased in esophageal biopsies from patients with active EoE compared with healthy controls or patients in remission and identifies an esophageal suprabasal epithelial cell subpopulation that uniquely expressed the core EoE proinflammatory transcriptome genes (CCL26, ALOX15, CAPN14, ANO1, and TNFAIP6). CONCLUSIONS: These studies identify SFRP1 as a key regulator of IL-13-induced and STAT3-dependent esophageal proliferation and BZH in EoE and link SFRP1+ esophageal epithelial cells with the proinflammatory and epithelial remodeling response in EoE.

Acute systemic myeloid inflammatory and stress response in severe food allergic reactions.

INTRODUCTION: Food allergic reactions can be severe and potentially life-threatening and the underlying immunological processes that contribute to the severity of reactions are poorly understood. The aim of this study is to integrate bulk RNA-sequencing of human and mouse peripheral blood mononuclear cells during food allergic reactions and in vivo mouse models of food allergy to identify dysregulated immunological processes associated with severe food allergic reactions. METHODS: Bulk transcriptomics of whole blood from human and mouse following food allergic reactions combined with integrative differential expressed gene bivariate and module eigengene network analyses to identify the whole blood transcriptome associated with food allergy severity. In vivo validation immune cell and gene expression in mice following IgE-mediated reaction. RESULTS: Bulk transcriptomics of whole blood from mice with different severity of food allergy identified gene ontology (GO) biological processes associated with innate and inflammatory immune responses, dysregulation of MAPK and NFkB signalling and identified 429 genes that correlated with reaction severity. Utilizing two independent human cohorts, we identified 335 genes that correlated with severity of peanut-induced food allergic reactions. Mapping mouse food allergy severity transcriptome onto the human transcriptome revealed 11 genes significantly dysregulated and correlated with severity. Analyses of whole blood from mice undergoing an IgE-mediated reaction revealed a rapid change in blood leukocytes particularly inflammatory monocytes (Ly6Chi Ly6G- ) and neutrophils that was associated with changes in CLEC4E, CD218A and GPR27 surface expression. CONCLUSIONS: Collectively, IgE-mediated food allergy severity is associated with a rapid innate inflammatory response associated with acute cellular stress processes and dysregulation of peripheral blood inflammatory myeloid cell frequencies.

Eosinophilic esophagitis: Immune mechanisms and therapeutic targets.

Eosinophilic esophagitis (EoE) is an emerging chronic inflammatory disease of the oesophagus and is clinically characterized by upper gastrointestinal (GI) symptoms including dysphagia and esophageal food impaction. Histopathologic manifestations, which include intraepithelial eosinophilic inflammation and alterations of the esophageal squamous epithelium, such as basal zone hyperplasia (BZH) and dilated intercellular spaces (DIS), are thought to contribute to esophageal dysfunction and disease symptoms. Corroborative clinical and discovery science-based studies have established that EoE is characterized by an underlying allergic inflammatory response, in part, related to the IL-13/CCL26/eosinophil axis driving dysregulation of several key epithelial barrier and proliferative regulatory genes including kallikrein (KLK) serine proteases, calpain 14 (CAPN14) and anoctamin 1 (ANO1). The contribution of these inflammatory and proliferative processes to the clinical and histological manifestations of disease are not fully elucidated. Herein, we discuss the immune molecules and cells that are thought to underlie the clinical and pathologic manifestations of EoE and the emerging therapeutics targeting these processes for the treatment of EoE.

IL-4-BATF signaling directly modulates IL-9 producing mucosal mast cell (MMC9) function in experimental food allergy.

BACKGROUND: This study group has previously identified IL-9-producing mucosal mast cell (MMC9) as the primary source of IL-9 to drive intestinal mastocytosis and experimental IgE-mediated food allergy. However, the molecular mechanisms that regulate the expansion of MMC9s remain unknown. OBJECTIVES: This study hypothesized that IL-4 regulates MMC9 development and MMC9-dependent experimental IgE-mediated food allergy. METHODS: An epicutaneous sensitization model was used and bone marrow reconstitution experiments were performed to test the requirement of IL-4 receptor α (IL-4Rα) signaling on MMC9s in experimental IgE-mediated food allergy. Flow cytometric, bulk, and single-cell RNA-sequencing analyses on small intestine (SI) MMC9s were performed to illuminate MMC9 transcriptional signature and the effect of IL-4Rα signaling on MMC9 function. A bone marrow-derived MMC9 culture system was used to define IL-4-BATF signaling in MMC9 development. RESULTS: Epicutaneous sensitization- and bone marrow reconstitution-based models of IgE-mediated food allergy revealed an IL-4 signaling-dependent cell-intrinsic effect on SI MMC9 accumulation and food allergy severity. RNA-sequencing analysis of SI-MMC9s identified 410 gene transcripts reciprocally regulated by IL-4 signaling, including Il9 and Batf. Insilico analyses identified a 3491-gene MMC9 transcriptional signature and identified 2 transcriptionally distinct SI MMC9 populations enriched for metabolic or inflammatory programs. Employing an in vitro MMC9-culture model system showed that generation of MMC9-like cells was induced by IL-4 and this was in part dependent on BATF. CONCLUSIONS: IL-4Rα signaling directly modulates MMC9 function and exacerbation of experimental IgE-mediated food allergic reactions. IL-4Rα regulation of MMC9s is in part BATF-dependent and occurs via modulation of metabolic transcriptional programs.

Identification of anoctamin 1 (ANO1) as a key driver of esophageal epithelial proliferation in eosinophilic esophagitis.

BACKGROUND: The pathology of eosinophilic esophagitis (EoE) is characterized by eosinophil-rich inflammation, basal zone hyperplasia (BZH), and dilated intercellular spaces, and the underlying processes that drive the pathologic manifestations of the disease remain largely unexplored. OBJECTIVE: We sought to investigate the involvement of the calcium-activated chloride channel anoctamin 1 (ANO1) in esophageal proliferation and the histopathologic features of EoE. METHODS: We examined mRNA and protein expression of ANO1 in esophageal biopsy samples from patients with EoE and in mice with EoE. We performed molecular and cellular analyses and ion transport assays on an in vitro esophageal epithelial 3-dimensional model system (EPC2-ALI) and murine models of EoE to define the relationship between expression and function of ANO1 and esophageal epithelial proliferation in patients with EoE. RESULTS: We observed increased ANO1 expression in esophageal biopsy samples from patients with EoE and in mice with EoE. ANO1 was expressed within the esophageal basal zone, and expression correlated positively with disease severity (eosinophils/high-power field) and BZH. Using an in vitro esophageal epithelial 3-dimensional model system revealed that ANO1 undergoes chromatin modification and rapid upregulation of expression after IL-13 stimulation, that ANO1 is the primary apical IL-13-induced Cl- transport mechanism within the esophageal epithelium, and that loss of ANO1-dependent Cl- transport abrogated esophageal epithelial proliferation. Mechanistically, ANO1-dependent regulation of basal cell proliferation was associated with modulation of TP63 expression and phosphorylated cyclin-dependent kinase 2 levels. CONCLUSIONS: These data identify a functional role for ANO1 in esophageal cell proliferation and BZH in patients with EoE and provide a rationale for pharmacologic intervention of ANO1 function in patients with EoE.

Modeling TH 2 responses and airway inflammation to understand fundamental mechanisms regulating the pathogenesis of asthma.

In this review, we highlight experiments conducted in our laboratories that have elucidated functional roles for CD4+ T-helper type-2 lymphocytes (TH 2 cells), their associated cytokines, and eosinophils in the regulation of hallmark features of allergic asthma. Notably, we consider the complexity of type-2 responses and studies that have explored integrated signaling among classical TH 2 cytokines (IL-4, IL-5, and IL-13), which together with CCL11 (eotaxin-1) regulate critical aspects of eosinophil recruitment, allergic inflammation, and airway hyper-responsiveness (AHR). Among our most important findings, we have provided evidence that the initiation of TH 2 responses is regulated by airway epithelial cell-derived factors, including TRAIL and MID1, which promote TH 2 cell development via STAT6-dependent pathways. Further, we highlight studies demonstrating that microRNAs are key regulators of allergic inflammation and potential targets for anti-inflammatory therapy. On the background of TH 2 inflammation, we have demonstrated that innate immune cells (notably, airway macrophages) play essential roles in the generation of steroid-resistant inflammation and AHR secondary to allergen- and pathogen-induced exacerbations. Our work clearly indicates that understanding the diversity and spatiotemporal role of the inflammatory response and its interactions with resident airway cells is critical to advancing knowledge on asthma pathogenesis and the development of new therapeutic approaches.

Manipulating DNA damage-response signaling for the treatment of immune-mediated diseases.

Antigen-activated lymphocytes undergo extraordinarily rapid cell division in the course of immune responses. We hypothesized that this unique aspect of lymphocyte biology leads to unusual genomic stress in recently antigen-activated lymphocytes and that targeted manipulation of DNA damage-response (DDR) signaling pathways would allow for selective therapeutic targeting of pathological T cells in disease contexts. Consistent with these hypotheses, we found that activated mouse and human T cells display a pronounced DDR in vitro and in vivo. Upon screening a variety of small-molecule compounds, we found that potentiation of p53 (via inhibition of MDM2) or impairment of cell cycle checkpoints (via inhibition of CHK1/2 or WEE1) led to the selective elimination of activated, pathological T cells in vivo. The combination of these strategies [which we termed "p53 potentiation with checkpoint abrogation" (PPCA)] displayed therapeutic benefits in preclinical disease models of hemophagocytic lymphohistiocytosis and multiple sclerosis, which are driven by foreign antigens or self-antigens, respectively. PPCA therapy targeted pathological T cells but did not compromise naive, regulatory, or quiescent memory T-cell pools, and had a modest nonimmune toxicity profile. Thus, PPCA is a therapeutic modality for selective, antigen-specific immune modulation with significant translational potential for diverse immune-mediated diseases.

Loss of GTPase of immunity-associated protein 5 (Gimap5) promotes pathogenic CD4+ T-cell development and allergic airway disease.

BACKGROUND: GTPase of immunity-associated protein 5 (GIMAP5) is essential for lymphocyte homeostasis and survival. Recently, human GIMAP5 single nucleotide polymorphisms have been linked to an increased risk for asthma, whereas loss of Gimap5 in mice has been associated with severe CD4+ T cell-driven immune pathology. OBJECTIVE: We sought to identify the molecular and cellular mechanisms by which Gimap5 deficiency predisposes to allergic airway disease. METHODS: CD4+ T-cell polarization and development of pathogenic CD4+ T cells were assessed in Gimap5-deficient mice and a human patient with a GIMAP5 loss-of-function (LOF) mutation. House dust mite-induced airway inflammation was assessed by using a complete Gimap5 LOF (Gimap5sph/sph) and conditional Gimap5fl/flCd4Cre/ert2 mice. RESULTS: GIMAP5 LOF mutations in both mice and human subjects are associated with spontaneous polarization toward pathogenic TH17 and TH2 cells in vivo. Mechanistic studies in vitro reveal that impairment of Gimap5-deficient TH cell differentiation is associated with increased DNA damage, particularly during TH1-polarizing conditions. DNA damage in Gimap5-deficient CD4+ T cells could be controlled by TGF-ß, thereby promoting TH17 polarization. When challenged with house dust mite in vivo, Gimap5-deficient mice displayed an exacerbated asthma phenotype (inflammation and airway hyperresponsiveness), with increased development of TH2, TH17, and pathogenic TH17/TH2 cells. CONCLUSION: Activation of Gimap5-deficient CD4+ T cells is associated with increased DNA damage and reduced survival that can be overcome by TGF-ß. This leads to selective survival of pathogenic TH17 cells but also TH2 cells in human subjects and mice, ultimately promoting allergic airway disease.

17ß-Estradiol protects the esophageal epithelium from IL-13-induced barrier dysfunction and remodeling.

BACKGROUND: The incidence of eosinophilic esophagitis (EoE) is greater in male than female subjects, and the underlying molecular basis for this sex bias remains unclear. OBJECTIVE: We sought to delineate the contribution of the sex hormone estrogen to the EoE phenotype and esophageal epithelial barrier function and remodeling. METHODS: We performed demographic and incidence analyses of EoE in male and female subjects from a single-center pediatric cohort. Estrogen-responsive gene expression analyses and estrogen receptor (ESR) immunofluorescence staining of esophageal biopsy specimens from patients with EoE and control subjects were performed. The effect of 17ß-estradiol (E2) on IL-13-induced signaling pathways, gene expression, and esophageal epithelial architecture and barrier function in a primary human esophageal keratinocyte cell (EPC2) culture system (EPC2-air-liquid interface) was examined. RESULTS: We observed a male predominance in patients with EoE. Analyses of RNA sequencing data sets revealed a significant dysregulation of the estrogen-responsive gene network and expression of ESR1 and ESR2 in esophageal biopsy specimens from patients with EoE compared with control subjects. IL-13 stimulation of EPC2-air-liquid interface cells led to altered cellular architecture with induced dilation of intercellular spaces and barrier dysfunction. Pretreatment of EPC2s with E2 prior to IL-13 exposure abrogated IL-13-induced architectural changes and esophageal barrier dysfunction. Mechanistically, E2-protective effects were dependent on ESR2 and associated with diminishing of IL-13-induced tyrosine kinase 2 and signal transducer and activator of transcription 6 phosphorylation and EoE-dysregulated gene expression. CONCLUSIONS: Estrogen-responsive genes are modified in patients with EoE compared with control subjects. E2 attenuated IL-13-induced architectural changes and esophageal epithelial barrier dysfunction through inhibition of the IL-13/tyrosine kinase 2/signal transducer and activator of transcription 6 pathway via ESR2-dependent process. Estrogen hormone signaling may protect against development of EoE in female subjects.

IL-13-induced intestinal secretory epithelial cell antigen passages are required for IgE-mediated food-induced anaphylaxis.

BACKGROUND: Food-induced anaphylaxis (FIA) is an IgE-dependent immune response that can affect multiple organs and lead to life-threatening complications. The processes by which food allergens cross the mucosal surface and are delivered to the subepithelial immune compartment to promote the clinical manifestations associated with food-triggered anaphylaxis are largely unexplored. OBJECTIVE: We sought to define the processes involved in the translocation of food allergens across the mucosal epithelial surface to the subepithelial immune compartment in FIA. METHODS: Two-photon confocal and immunofluorescence microscopy was used to visualize and trace food allergen passage in a murine model of FIA. A human colon cancer cell line, RNA silencing, and pharmacologic approaches were used to identify the molecular regulation of intestinal epithelial allergen uptake and translocation. Human intestinal organoid transplants were used to demonstrate the conservation of these molecular processes in human tissues. RESULTS: Food allergens are sampled by using small intestine (SI) epithelial secretory cells (termed secretory antigen passages [SAPs]) that are localized to the SI villous and crypt region. SAPs channel food allergens to lamina propria mucosal mast cells through an IL-13-CD38-cyclic adenosine diphosphate ribose (cADPR)-dependent process. Blockade of IL-13-induced CD38/cADPR-dependent SAP antigen passaging in mice inhibited induction of clinical manifestations of FIA. IL-13-CD38-cADPR-dependent SAP sampling of food allergens was conserved in human intestinal organoids. CONCLUSION: We identify that SAPs are a mechanism by which food allergens are channeled across the SI epithelium mediated by the IL-13/CD38/cADPR pathway, regulate the onset of FIA reactions, and are conserved in human intestine.

Developments in the mechanisms of allergy in 2018 through the eyes of Clinical and Experimental Allergy, Part I.

In the first of two linked articles, we describe the development in the mechanisms underlying allergy as described by Clinical & Experimental Allergy and other journals in 2018. Experimental models of allergic disease, basic mechanisms and clinical mechanisms are all covered.

C5a receptor 1-/- mice are protected from the development of IgE-mediated experimental food allergy.

BACKGROUND: Food-induced anaphylaxis is a serious allergic reaction caused by Fcε-receptor activation on mast cells (MCs). The exact mechanisms breaking oral tolerance and the effector pathways driving food allergy remain elusive. As complement is activated in food-induced anaphylaxis, we aimed to assess the role of C5a in disease pathogenesis. METHODS: Oral antigen-induced food-induced anaphylaxis was induced in BALB/c wild-type (wt) and C5ar1-/- mice. Readouts included diarrhea development, changes in rectal temperature, hematocrit, antigen-specific serum IgE, MCPT-1, and intestinal MC numbers, as well as FcεR1-mediated MC functions including C5a receptor 1 (C5aR1) regulation. Further, histamine-mediated hypothermia and regulation of endothelial tight junctions were determined. RESULTS: Repeated oral OVA challenge resulted in diarrhea, hypothermia, increased hematocrit, high OVA-specific serum IgE, and MCPT-1 levels in wt mice. Male C5ar1-/- mice were completely whereas female C5ar1-/- mice were partially protected from anaphylaxis development. Serum MCPT-1 levels were reduced gender-independent, whereas IgE levels were reduced in male but not in female C5ar1-/- mice. Mechanistically, IgE-mediated degranulation and IL-6 production from C5ar1-/- BMMCs of both sexes were significantly reduced. Importantly, FcεR1 cross-linking strongly upregulated C5aR1 MC expression in vitro and in vivo. Finally, C5ar1-/- male mice were largely protected from histamine-induced hypovolemic shock, which was associated with protection from histamine-induced barrier dysfunction in vitro following C5aR targeting. CONCLUSIONS: Our findings identify C5aR1 activation as an important driver of IgE-mediated food allergy through regulation of allergen-specific IgE production, FcεR1-mediated MC degranulation, and histamine-driven effector functions preferentially in male mice.

The vascular endothelial specific IL-4 receptor alpha-ABL1 kinase signaling axis regulates the severity of IgE-mediated anaphylactic reactions.

BACKGROUND: Severe IgE-mediated, food-induced anaphylactic reactions are characterized by pulmonary venous vasodilatation and fluid extravasation, which are thought to lead to the life-threatening anaphylactic phenotype. The underlying immunologic and cellular processes involved in driving fluid extravasation and the severe anaphylactic phenotype are not fully elucidated. OBJECTIVE: We sought to define the interaction and requirement of IL-4 and vascular endothelial (VE) IL-4 receptor α chain (IL-4Rα) signaling in histamine-abelson murine leukemia viral oncogene homology 1 (ABL1)-mediated VE dysfunction and fluid extravasation in the severity of IgE-mediated anaphylactic reactions in mice. METHODS: Mice deficient in VE IL-4Rα and models of passive and active oral antigen- and IgE-induced anaphylaxis were used to define the requirements of the VE IL-4Rα and ABL1 pathway in severe anaphylactic reactions. The human VE cell line (EA.hy926 cells) and pharmacologic (imatinib) and genetic (short hairpin RNA knockdown of IL4RA and ABL1) approaches were used to define the requirement of this pathway in VE barrier dysfunction. RESULTS: IL-4 exacerbation of histamine-induced hypovolemic shock in mice was dependent on VE expression of IL-4Rα. IL-4- and histamine-induced ABL1 activation in human VE cells and VE barrier dysfunction was ABL1-dependent. Development of severe IgE-mediated hypovolemia and shock required VE-restricted ABL1 expression. Treatment of mice with a history of food-induced anaphylaxis with the ABL kinase inhibitor imatinib protected the mice from severe IgE-mediated anaphylaxis. CONCLUSION: IL-4 amplifies IgE- and histamine-induced VE dysfunction, fluid extravasation, and the severity of anaphylaxis through a VE IL-4Rα/ABL1-dependent mechanism. These studies implicate an important contribution by the VE compartment in the severity of anaphylaxis and identify a new pathway for therapeutic intervention of IgE-mediated reactions.

Solute carrier family 9, subfamily A, member 3 (SLC9A3)/sodium-hydrogen exchanger member 3 (NHE3) dysregulation and dilated intercellular spaces in patients with eosinophilic esophagitis.

BACKGROUND: Eosinophilic esophagitis (EoE) is characterized by histopathologic modifications of esophageal tissue, including eosinophil-rich inflammation, basal zone hyperplasia, and dilated intercellular spaces (DIS). The underlying molecular processes that drive the histopathologic features of EoE remain largely unexplored. OBJECTIVE: We sought to investigate the involvement of solute carrier family 9, subfamily A, member 3 (SLC9A3) in esophageal epithelial intracellular pH (pHi) and DIS formation and the histopathologic features of EoE. METHODS: We examined expression of esophageal epithelial gene networks associated with regulation of pHi in the EoE transcriptome of primary esophageal epithelial cells and an in vitro esophageal epithelial 3-dimensional model system (EPC2-ALI). Molecular and cellular analyses and ion transport assays were used to evaluate the expression and function of SLC9A3. RESULTS: We identified altered expression of gene networks associated with regulation of pHi and acid-protective mechanisms in esophageal biopsy specimens from pediatric patients with EoE (healthy subjects, n = 6; patients with EoE, n = 10). The most dysregulated gene central to regulating pHi was SLC9A3. SLC9A3 expression was increased within the basal layer of esophageal biopsy specimens from patients with EoE, and expression positively correlated with disease severity (eosinophils/high-power field) and DIS (healthy subjects, n = 10; patients with EoE, n = 10). Analyses of esophageal epithelial cells revealed IL-13-induced, signal transducer and activator of transcription 6-dependent SLC9A3 expression and Na+-dependent proton secretion and that SLC9A3 activity correlated positively with DIS formation. Finally, we showed that IL-13-mediated, Na+-dependent proton secretion was the primary intracellular acid-protective mechanism within the esophageal epithelium and that blockade of SLC9A3 transport abrogated IL-13-induced DIS formation. CONCLUSIONS: SLC9A3 plays a functional role in DIS formation, and pharmacologic interventions targeting SLC9A3 function may suppress the histopathologic manifestations in patients with EoE.

Mucosal Expression of Type 2 and Type 17 Immune Response Genes Distinguishes Ulcerative Colitis From Colon-Only Crohn's Disease in Treatment-Naive Pediatric Patients.

BACKGROUND & AIMS: There is controversy regarding the role of the type 2 immune response in the pathogenesis of ulcerative colitis (UC)-few data are available from treatment-naive patients. We investigated whether genes associated with a type 2 immune response in the intestinal mucosa are up-regulated in treatment-naive pediatric patients with UC compared with patients with Crohn's disease (CD)-associated colitis or without inflammatory bowel disease (IBD), and whether expression levels are associated with clinical outcomes. METHODS: We used a real-time reverse-transcription quantitative polymerase chain reaction array to analyze messenger RNA (mRNA) expression patterns in rectal mucosal samples from 138 treatment-naive pediatric patients with IBD and macroscopic rectal disease, as well as those from 49 children without IBD (controls), enrolled in a multicenter prospective observational study from 2008 to 2012. Results were validated in real-time reverse-transcription quantitative polymerase chain reaction analyses of rectal RNA from an independent cohort of 34 pediatric patients with IBD and macroscopic rectal disease and 17 controls from Cincinnati Children's Hospital Medical Center. RESULTS: We measured significant increases in mRNAs associated with a type 2 immune response (interleukin [IL]5 gene, IL13, and IL13RA2) and a type 17 immune response (IL17A and IL23) in mucosal samples from patients with UC compared with patients with colon-only CD. In a regression model, increased expression of IL5 and IL17A mRNAs distinguished patients with UC from patients with colon-only CD (P = .001; area under the receiver operating characteristic curve, 0.72). We identified a gene expression pattern in rectal tissues of patients with UC, characterized by detection of IL13 mRNA, that predicted clinical response to therapy after 6 months (odds ratio [OR], 6.469; 95% confidence interval [CI], 1.553-26.94), clinical response after 12 months (OR, 6.125; 95% CI, 1.330-28.22), and remission after 12 months (OR, 5.333; 95% CI, 1.132-25.12). CONCLUSIONS: In an analysis of rectal tissues from treatment-naive pediatric patients with IBD, we observed activation of a type 2 immune response during the early course of UC. We were able to distinguish patients with UC from those with colon-only CD based on increased mucosal expression of genes that mediate type 2 and type 17 immune responses. Increased expression at diagnosis of genes that mediate a type 2 immune response is associated with response to therapy and remission in pediatric patients with UC.