IgE promotes type 2 innate lymphoid cells in murine food allergy

IgE-Mediated Activation of Mast Cells and Basophils in Health and Disease

Type 2-mediated immune responses protect the body against environmental threats at barrier surfaces, such as large parasites and environmental toxins, and facilitate the repair of inflammatory tissue damage. However, maladaptive responses to typically nonpathogenic substances, commonly known as allergens, can lead to the development of allergic diseases. Type 2 immunity involves a series of prototype TH2 cytokines (IL-4, IL-5, IL-13) and alarmins (IL-33, TSLP) that promote the generation of adaptive CD4+ helper Type 2 cells and humoral products such as allergen-specific IgE. Mast cells and basophils are integral players in this network, serving as primary effectors of IgE-mediated responses. These cells bind IgE via high-affinity IgE receptors (FcεRI) expressed on their surface and, upon activation by allergens, release a variety of mediators that regulate tissue responses, attract and modulate other inflammatory cells, and contribute to tissue repair. Here, we review the biology and effector mechanisms of these cells, focusing primarily on their role in mediating IgE responses in both physiological and pathological contexts.

Study on the Allergenicity of Tropomyosin from Different Aquatic Products Based on Conformational and Linear Epitopes Analysis

Tropomyosin (TM) is a major allergen in aquatic products. The aim of this study was to analyze the allergenicity of TM from different aquatic products based on conformational and linear epitopes. Structural and allergenicity analyses of TM were conducted using intrinsic fluorescence, UV absorption spectra, circular dichroism, and animal experiments. Epitope mapping was performed through bioinformatics software and a one-bead, one-compound (OBOC) peptide library screening approach. The results showed that the structures of TMs from different aquatic products are similar. Cross-reactivity was observed among TMs from different aquatic products, with fish-TM showing lower cross-reactivity compared with other TMs. Additionally, 13, 14, 11, 13, and 12 linear epitopes, along with 2, 2, 1, 2, and 3 conformational epitopes, were identified for shrimp-TM, crab-TM, fish-TM, oyster-TM, and clam-TM, respectively. Overall, these findings provide a basis for elucidating the epitope localization and allergenicity relationship of TMs from different aquatic products.

Identification and Allergenicity Analysis of Tropomyosin: A Heat-Stable Allergen in Lateolabrax japonicus

Lateolabrax japonicus, a prevalent aquatic delicacy, is known to elicit allergic reactions in certain individuals. Nevertheless, the investigation into its allergenic components has remained notably inadequate. In the research, an approximately 35 kDa heat-stable protein of L. japonicus raw/steamed extracts was verified as tropomyosin (TM) by LC-MS/MS. Open reading frame of TM (852 bp) was acquired via PCR amplification, encoding 284 amino acids. The IgE-binding frequency of TM expressed in Escherichia coli was 22.5% among 80 fish-sensitized patients. Furthermore, TM had the ability to activate basophils in 7 patients. In the Balb/c mice model, compared with the PBS group, the levels of specific antibodies (IgE, IgG1, and IgG2a), CD19+ B cells, IL-4, and IL-10 were significantly increased in the TM group. However, the opposite was indeed the case for CD4+ TCR-β, CD4+ CD25+ Fox p 3+ cells, and IFN-γ. These findings regarding an allergen assist in conducting component-resolved diagnoses and therapeutic research for fish allergy.

Oat β-(1 → 3, 1 → 4)-d-glucan alleviates food allergy-induced colonic injury in mice by increasing Lachnospiraceae abundance and butyrate production

Oat β-(1 → 3, 1 → 4)-d-glucan (OBG), a linear polysaccharide primarily found in oat bran, has been demonstrated to possess immunomodulatory properties and regulate gut microbiota. This study aimed to investigate the impact of low molecular weight (Mw) OBG (155.2 kDa) on colonic injury and allergic symptoms induced by food allergy (FA), and to explore its potential mechanism. In Experiment 1, results indicated that oral OBG improved colonic inflammation and epithelial barrier, and significantly relieved allergy symptoms. Importantly, the OBG supplement altered the gut microbiota composition, particularly increasing the abundance of Lachnospiraceae and its genera, and promoted the production of short-chain fatty acids, especially butyrate. However, in Experiment 2, the gut microbial depletion eliminated these protective effects of OBG on the colon in allergic mice. Further, in Experiment 3, fecal microbiota transplantation and sterile fecal filtrate transfer directly validated the role of OBG-mediated gut microbiota and its metabolites in relieving FA and its induced colonic injury. Our findings suggest that low Mw OBG can alleviate FA-induced colonic damage by increasing Lachnospiraceae abundance and butyrate production, and provide novel insights into the health benefits and mechanisms of dietary polysaccharide intervention for FA.

The influence on the structure and allergenicity of milk β-lactoglobulin by methylglyoxal during thermal processing

This study aims to investigate the effects of the typical glycation intermediate methylglyoxal (MGO) on the structure and allergenicity of milk β-lactoglobulin (βLG) during thermal processing. Structural changes were assessed using SDS-PAGE, intrinsic fluorescence, circular dichroism, and HPLC-MS/MS. Allergenicity was evaluated through in vitro and in vivo experiments. The conformational changes of βLG significantly were induced by MGO during heat treatment, with a 41.3% decrease in α-helix content and a 25.4% increase in random structure. Furthermore, the lysine, arginine, aspartic acid, and histidine residues in βLG were modified by MGO, which may disrupt or mask allergenic epitopes. Additionally, MGO treatment resulted in a reduction of 41.1% and 26.8% in the pro-inflammatory mediators histamine and β-hexosaminidase in KU812 cells, respectively. Additionally, cytokine levels of IL-4 and IL-13 were reduced by 26.3% and 21.75%, respectively. In mouse experiments, compared to the βLG group, the MGO-βLG group showed a 2-4 fold decrease in IgE, IgG, and IgG1 levels. After reacting with βLG, MGO can reduce serum histamine release by up to 73.9% and mast cell protease-1 (MCP-1) release by 40.8%. These results indicate that the typical glycation intermediate MGO can modify the allergenic epitopes of milk βLG during thermal processing, thereby affecting its allergenicity. This study provides a reference for elucidating the natural rules of allergenicity changes during milk thermal processing.

Innate lymphoid cells in immunoglobulin E-mediated food allergy

PURPOSE OF REVIEW

Recognition of the importance of innate lymphoid cells (ILCs) in the immune mechanisms of food allergy has grown in recent years. This review summarizes recent findings of ILCs in immunoglobulin E (IgE)-mediated food allergy. New research on ILCs in the context of the microbiome and other atopic diseases are also considered with respect to how they can inform understanding of the role of ILCs in food allergy.

RECENT FINDINGS

ILCs can mediate allergic and tolerogenic responses through multiple pathways. A novel subset of interleukin (IL)-10 producing ILC2s are associated with tolerance following immunotherapy to grass pollen, house dust mite allergy and lipid transfer protein allergy. ILC2s can drive food allergen-specific T cell responses in an antigen-specific manner. A memory subset of ILC2s has been identified through studies of other atopic diseases and is associated with effectiveness of response to therapy.

SUMMARY

The role of ILCs in food allergy and oral tolerance is relatively understudied compared to other diseases. ILCs can modulate immune responses through several mechanisms, and it is likely that these are of importance in the context of food allergy. Better understanding of theses pathways may help to answer fundamental questions regarding the development of food allergy and lead to novel therapeutic targets and treatment.

Maternal influences on offspring food allergy

The prevalence of allergies has been globally escalating. While allergies could appear at any age, they often develop in early life. However, the significant knowledge gap in the field is the mechanisms by which allergies affect certain people but not others. Investigating early factors and events in neonatal life that have a lasting impact on determining the susceptibilities of children to develop allergies is a significant area of the investigation as it promotes the understanding of neonatal immune system that mediates tolerance versus allergies. This review focuses on the research over the recent 10 years regarding the potential maternal factors that influence offspring allergies with a view to food allergy, a potentially life-threatening cause of anaphylaxis. The role of breast milk, maternal diet, maternal antibodies, and microbiota that have been suggested as key maternal factors regulating offspring allergies are discussed here. We also suggest future research area to expand our knowledge of maternal-offspring interactions on the pathogenesis of food allergy.

The potential of orally exposed risk factors and constituents aggravating food allergy: Possible mechanism and target cells

Food allergy is a significant concern for the health of humans worldwide. In addition to dietary exposure of food allergens, genetic and environmental factors also play an important role in the development of food allergy. However, only the tip of the iceberg of risk factors in food allergy has been identified. The importance of food allergy caused by orally exposed risk factors and constituents, including veterinary drugs, pesticides, processed foods/derivatives, nanoparticles, microplastics, pathogens, toxins, food additives, dietary intake of salt/sugar/total fat, vitamin D, and therapeutic drugs, are highlighted and discussed in this review. Moreover, the epithelial barrier hypothesis, which is closely associated with the occurrence of food allergy, is also introduced. Additionally, several orally exposed risk factors and constituents that have been reported to disrupt the epithelial barrier are elucidated. Finally, the possible mechanisms and key immune cells of orally exposed risk factors and constituents in aggravating food allergy are overviewed. Further work should be conducted to define the specific mechanism by which these risk factors and constituents are driving food allergy, which will be of central importance to the targeted therapy of food allergy.

Schistosoma excretory/secretory products: an untapped library of tolerogenic immunotherapeutics against food allergy

Food allergy (FA) is considered the 'second wave' of the allergy epidemic in developed countries after asthma and allergic rhinitis with a steadily growing burden of 40%. The absence of early childhood pathogen stimulation embodied by the hygiene hypothesis is one explanation, and in particular, the eradication of parasitic helminths could be at play. Infections with parasites Schistosoma spp. have been found to have a negative correlation with allergic diseases. Schistosomes induce regulatory responses to evade immune detection and ensure their long-term survival. This is achieved via excretory/secretory (E/S) products, consisting of proteins, lipids, metabolites, nucleic acids and extracellular vesicles, representing an untapped therapeutic avenue for the treatment of FA without the unpleasant side-effects and risks associated with live infection. Schistosome-derived immunotherapeutic development is in its infancy and novel discoveries are heavily technology dependent; thus, it is essential to better understand how newly identified molecules interact with host immune systems to ensure safety and successful translation. This review will outline the identified Schistosoma-derived E/S products at all life cycle stages and discuss known mechanisms of action and their ability to suppress FA.

Atopic dermatitis and IgE-mediated food allergy: Common biologic targets for therapy and prevention

OBJECTIVE

To highlight common mechanistic targets for the treatment of atopic dermatitis (AD) and IgE-mediated food allergy (IgE-FA) with potential to be effective for both diseases and prevent atopic progression.

DATA SOURCES

Data sources were PubMed searches or National Clinical Trials (NCT)-registered clinical trials related to AD, IgE-FA, and other atopic conditions, especially focused on the pediatric population.

STUDY SELECTIONS

Human seminal studies and/or articles published in the past decade were emphasized with reference to preclinical models when relevant. NCT-registered clinical trials were filtered by inclusion of pediatric subjects younger than 18 years with special focus on children younger than 12 years as a critical period when AD and IgE-FA diseases may often be concurrent.

RESULTS

AD and IgE-FA share several pathophysiologic features, including epithelial barrier dysfunction, innate and adaptive immune abnormalities, and microbial dysbiosis, which may be critical for the clinical progression between these diseases. Revolutionary advances in targeted biologic therapies have shown the benefit of inhibiting type 2 immune responses, using dupilumab (anti-interleukin-4Rα) or omalizumab (anti-IgE), to potentially reduce symptom burden for both diseases in pediatric populations. Although the potential for biologics to promote disease remission (AD) or sustained unresponsiveness (IgE-FA) remains unclear, the refinement of biomarkers to predict infants at risk for atopic disorders provides promise for prevention through timely intervention.

CONCLUSION

AD and IgE-FA exhibit common features that may be leveraged to develop biologic therapeutic strategies to treat both conditions and even prevent atopic progression. Future studies should be designed with consistent age stratification in the pediatric population and standardized regimens of adjuvant oral immunotherapy or dose escalation (IgE-FA) to improve cross-study interpretation.

Effects of Glycosylation Combined with Phosphate Treatment on the Allergenicity and Structure of Tropomyosin in Litopenaeus vannamei

Tropomyosin (TM) is the main allergen in shrimp (Litopenaeus vannamei). In this study, the effects of allergenicity and structure of TM by glycosylation (GOS-TM), phosphate treatment (SP-TM), and glycosylation combined with phosphate treatment (GOS-SP-TM) were investigated. Compared to GOS-TM and SP-TM, the IgG/IgE binding capacity of GOS-SP-TM was significantly decreased with 63.9 ± 2.0 and 49.7 ± 2.7%, respectively. Meanwhile, the α-helix content reduced, surface hydrophobicity increased, and 10 specific amino acids (K30, K38, S39, K48, K66, K74, K128, K161, S210, and K251) were modified by glycosylation on six IgE linear epitopes of GOS-SP-TM. In the BALB/c mice allergy model, GOS-SP-TM could significantly reduce the levels of specific IgE, IgG1, and CD4+IL-4+, while the levels of IgG2a, CD4+CD25+Foxp3+, and CD4+IFN-γ+ were increased, which equilibrated Th1 and Th2 cells, thus alleviating allergic symptoms. These results indicated that glycosylation combined with phosphate treatment can provide a new insight into developing hypoallergenic shrimp food.

Reducing the Allergenicity of β-Lactoglobulin by Covalent Modification with Different Contents of Epigallocatechin Gallate (EGCG): In Vitro and In Vivo Studies

β-Lactoglobulin (βLG) is a major allergen in bovine milk protein. This study was designed to investigate changes in βLG structure, digestibility, and allergenicity induced by covalent binding modification with different contents of (-)-epigallocatechin 3-gallate (EGCG). The reaction of EGCG conjugation with βLG reached saturation at a molar ratio of 1:60 βLG:EGCG. Conjugation with EGCG altered the βLG structure, decreased IgE-binding capacity, and increased digestibility in a dose-dependent manner. In vivo studies showed that covalent conjugation with EGCG can reduce βLG-induced allergic symptoms with reducing levels of IgE, histamine, and mast cell protease-1 (mMCP-1) and the percentage of sensitized mast cells. Allergenicity was reduced more effectively in saturated βLG-EGCG conjugates compared to semisaturated conjugates. Observed changes in IFN-γ, IL-4, IL-5, IL-10, and TGF-β levels suggested that βLG-EGCG conjugates were able to promote Th1/Th2 immune balance. These findings further our understanding of the relationship between the degree of polyphenol conjugation and the allergenicity of food allergens.

Allergen-specific IgA and IgG antibodies as inhibitors of mast cell function in food allergy

Food allergy, a group of adverse immune responses to normally innocuous food protein antigens, is an increasingly prevalent public health issue. The most common form is IgE-mediated food allergy in which food antigen-induced crosslinking of the high-affinity IgE-receptor, FcεRI, on the surface of mast cells triggers the release of inflammatory mediators that contribute to a wide range of clinical manifestations, including systemic anaphylaxis. Mast cells also play a critical function in adaptive immunity to foods, acting as adjuvants for food-antigen driven Th2 cell responses. While the diagnosis and treatment of food allergy has improved in recent years, no curative treatments are currently available. However, there is emerging evidence to suggest that both allergen-specific IgA and IgG antibodies can counter the activating effects of IgE antibodies on mast cells. Most notably, both antigen-specific IgA and IgG antibodies are induced in the course of oral immunotherapy. In this review, we highlight the role of mast cells in food allergy, both as inducers of immediate hypersensitivity reactions and as adjuvants for type 2 adaptive immune responses. Furthermore, we summarize current understanding of the immunomodulatory effects of antigen-specific IgA and IgG antibodies on IgE-induced mast cell activation and effector function. A more comprehensive understanding of the regulatory role of IgA and IgG in food allergy may provide insights into physiologic regulation of immune responses to ingested antigens and could seed novel strategies to treat allergic disease.

Group 2 innate lymphoid cells are key in lipid transfer protein allergy pathogenesis

Background

Immunopathology in food allergy is characterized by an uncontrolled type 2 immune response and specific-IgE production. Recent studies have determined that group 2 innate lymphoid cells (ILC2) participate in the food allergy pathogenic mechanism and their severity. Our objective was to investigate the role of ILC2 in peach-allergic patients due to non-specific lipid transfer protein (Pru p 3) sensitization.

Methods

The immune response in peripheral blood mononuclear cells was characterized in lipid transfer protein-allergic patients and healthy controls. We have analyzed the Pru p 3 uptake on ILC2, the expression of costimulatory molecules, and their involvement on the T-cell proliferative response and cytokine production under different experimental conditions: cytokines involved in group 2 innate lymphoid cell activation (IL-33 and IL-25), Pru p 3 as main food allergen, and the combination of both components (IL-33/IL-25+Pru p 3) using cell sorting, EliSpot, flow cytometry, and confocal microscopy.

Results

Our results show that Pru p 3 allergen is taken up by group 2 innate lymphoid cells, regulating their costimulatory molecule expression (CD83 and HLA-DR) depending on the presence of Pru p 3 and its combination with IL-33/IL-25. The Pru p 3-stimulated ILC2 induced specific GATA3+Th2 proliferation and cytokine (IL-4, IL-5, and IL-13) production in lipid transfer protein-allergic patients in a cell contact-dependent manner with no changes in Tbet+Th1- and FOXP3+Treg cell differentiation.

Conclusions

The results indicate that in lipid transfer protein-allergic patients, the responsible allergen, Pru p 3, interacts with group 2 innate lymphoid cells, promoting a Th2 cell response. Our results might be of interest in vivo, as they show a role of group 2 innate lymphoid cells as antigen-presenting cells, contributing to the development of food allergy. Consequently, group 2 innate lymphoid cells may be considered as potential therapeutic targets.

The Prostaglandin D2 Receptor CRTH2 Contributes to Airway Hyperresponsiveness during Airway Inflammation Induced by Sensitization without an Adjuvant in Mice

INTRODUCTION

Prostaglandin D2 (PGD2), which is produced mainly by Th2 cells and mast cells, promotes a type-2 immune response by activating Th2 cells, mast cells, eosinophils, and group 2 innate lymphoid cells (ILC2s) via its receptor, chemoattractant receptor-homologous molecules on Th2 cells (CRTH2). However, the role of CRTH2 in models of airway inflammation induced by sensitization without adjuvants, in which both IgE and mast cells may play major roles, remain unclear.

METHODS

Wild-type (WT) and CRTH2-knockout (KO) mice were sensitized with ovalbumin (OVA) without an adjuvant and then challenged intranasally with OVA. Airway inflammation was assessed based on airway hyperresponsiveness (AHR), lung histology, number of leukocytes, and levels of type-2 cytokines in the bronchoalveolar lavage fluid (BALF).

RESULTS

AHR was significantly reduced after OVA challenge in CRTH2 KO mice compared to WT mice. The number of eosinophils, levels of type-2 cytokines (IL-4, IL-5, and IL-13) in BALF, and IgE concentration in serum were decreased in CRTH2 KO mice compared to WT mice. However, lung histological changes were comparable between WT and CRTH2 KO mice.

CONCLUSION

CRTH2 is responsible for the development of asthma responses in a mouse model of airway inflammation that features prominent involvement of both IgE and mast cells.

Reducing the allergenicity of tropomyosin in shrimp by covalent conjugation with quercetin and chlorogenic acid

The study aimed to assay the allergenicity of shrimp tropomyosin (TM) following covalent conjugation with quercetin (QR) and chlorogenic acid (CA). The structure of the TM-polyphenol covalent conjugates was examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD), fluorescence, differential scanning calorimetry (DSC), and Fourier Transform infrared spectroscopy (FTIR). Potential allergenicity was evaluated using in vitro and in vivo methods. The results showed that QR and CA induced structural changes in TM through aggregation. RBL-2H3 cell results showed that TM-QR and TM-CA covalent conjugates reduced the release of β-hexosaminidase and histamine, respectively. In the mice model, TM-QR and TM-CA covalent conjugates reduced the level of IgE, IgG, IgG1, histamine, and mMCP-1 in sera. Furthermore, the allergenicity was reduced by suppressing Th2-related cytokines (IL-4, IL-5, IL-13) and promoting Th1-related cytokines (IFN-γ). These research findings demonstrate that the covalent binding of TM with QR and CA, modifies the allergenic epitopes of shrimp TM, thereby reducing its potential allergenicity. This approach holds practical applications in the production of low-allergenicity food within the food industry.

Potential Indications of Dupilumab in Th-2 Inflammatory Disease

Dupilumab is a fully humanized IgG4 monoclonal antibody, inhibiting IL-4 and IL-13 signaling, which are the main cytokines involved in type 2 inflammatory diseases. Its introduction was a breakthrough in the treatment of moderate-to-severe atopic dermatitis, but it is also used in other inflammatory diseases, including asthma, eosinophilic esophagitis and chronic rhinosinusitis with nasal polyposis. Recent advances in the understanding of inflammatory pathways have revealed that Th2-type inflammation is involved in a wider range of diseases than previously thought. The aim of our review is to examine off-label therapeutic indications of dupilumab, including bullous dermatoses (pemphigus, bullous pemphigoid) and alopecia areata, and to investigate its potential applications in cancer patients on anti-PD1 therapy.

Modulating the allergenicity and functional properties of peanut protein by covalent conjugation with polyphenols

Peanut protein is a common food allergen. Our previous study demonstrated that the allergenicity of Ara h1 declines after covalent conjugation with polyphenols in vitro; however, how polyphenols affect the structure, function, and allergenicity of peanut protein extract (PPE) after covalent conjugating needs clarifying. Here, we assessed how the structure, function, and allergenicity of PPE changed after covalent conjugation with epigallocatechin-3-gallate (PPE-EGCG) and chlorogenic acid (PPE-CA). PPE covalently conjugated with EGCG and CA using the alkali treatment method. Multi-spectroscopy showed that the structure of PPE-EGCG/CA conjugate changed, becoming less folded. In contrast, the functional properties of PPE significantly improved. The allergenicity of PPE-EGCG/CA significantly declined in vitro and in vivo experiments. Our findings confirm that covalent conjugation of PPE with EGCG and CA reduces the allergenicity and improves the functional properties of PPE by changing the structure of the protein.

Exploring potential pharmacological mechanisms of Yiqi Tuomin Decoction in the treatment of allergic rhinitis utilizing network pharmacology prediction and molecular docking-based strategies: experimental research

Yiqi Tuomin Decoction (YTD), which originated from the theory of lung deficiency and cold in Chinese medicine, is a common Chinese herbal formula used against allergic rhinitis (AR). In our otolaryngology department, this prescription has been used to treat so many AR patients with lung-deficiency-related colds for nearly 30 years. However, the mechanism of its ingredient-target is still unclear. Based on our early experiments and clinical case studies, in this paper, we explore the mechanism of YTD systematically against AR using bioinformatic methods of network pharmacology and molecular docking.

Methods

The Traditional Chinese Medicine Systems Pharmacology (TCMSP) database was used to screen the active ingredients and targets of YTD. The AR-related targets were retrieved from OMIM, GeneCards, TTD, DisGeNET, DrugBank databases, and PharmGKB. The Venn database was used to screen the potential core targets. After that, the STRING database was used to construct the protein-protein interaction (PPI) of the core targets and then visualize it by Cytoscape. The Gene Ontology (GO)-enriched processes and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of the core targets were analyzed by the KOBAS-I database and Sangerbox. Molecular docking was used to assess interactions between potential targets and active ingredients.

Results

A total of 169 active ingredients and 238 targets of YTD were predicted. YTD shared 115 common targets with AR from the Venn database. The GO-enriched processes and KEGG pathways indicate that genes involved in inflammation and oxidative stress, accompanying the MAPK signaling pathway, Th17 cell differentiation, IL-17 signaling pathway, and Th1 and Th2 cell differentiation, may play a mediated effect in YTD. The docking results showed good binding ability between the active ingredients and the selected targets.

Conclusions

Our study systematically indicated the underlying mechanism of YTD against AR from the perspective of bioinformatics. By studying the active ingredients of YTD, we obtained molecular mechanisms and established a reliable method and molecular theoretical basis for the sensible development of Chinese medicine in the treatment of AR.

Trained innate immunity, epigenetics, and food allergy

In recent years the increased incidence of food allergy in Western culture has been associated with environmental factors and an inappropriate immune phenotype. While the adaptive immune changes in food allergy development and progression have been well-characterized, an increase in innate cell frequency and activation status has also recently received greater attention. Early in prenatal and neonatal development of human immunity there is a reliance on epigenetic and metabolic changes that stem from environmental factors, which are critical in training the immune outcomes. In the present review, we discuss how trained immunity is regulated by epigenetic, microbial and metabolic factors, and how these factors and their impact on innate immunity have been linked to the development of food allergy. We further summarize current efforts to use probiotics as a potential therapeutic approach to reverse the epigenetic and metabolic signatures and prevent the development of severe anaphylactic food allergy, as well as the potential use of trained immunity as a diagnostic and management strategy. Finally, trained immunity is presented as one of the mechanisms of action of allergen-specific immunotherapy to promote tolerogenic responses in allergic individuals.

Crosstalk between the gut microbiota and innate lymphoid cells in intestinal mucosal immunity

The human gastrointestinal mucosa is colonized by thousands of microorganisms, which participate in a variety of physiological functions. Intestinal dysbiosis is closely associated with the pathogenesis of several human diseases. Innate lymphoid cells (ILCs), which include NK cells, ILC1s, ILC2s, ILC3s and LTi cells, are a type of innate immune cells. They are enriched in the mucosal tissues of the body, and have recently received extensive attention. The gut microbiota and its metabolites play important roles in various intestinal mucosal diseases, such as inflammatory bowel disease (IBD), allergic disease, and cancer. Therefore, studies on ILCs and their interaction with the gut microbiota have great clinical significance owing to their potential for identifying pharmacotherapy targets for multiple related diseases. This review expounds on the progress in research on ILCs differentiation and development, the biological functions of the intestinal microbiota, and its interaction with ILCs in disease conditions in order to provide novel ideas for disease treatment in the future.

Mast cells in food allergy: Inducing immediate reactions and shaping long-term immunity

Mast cells are distributed throughout the gastrointestinal tract and function as the main effector cells of IgE-mediated allergic reactions to foods. Allergen-induced cross-linking of IgE antibodies bound to high-affinity IgE receptors, FcεRI, on the surface of mast cells triggers their activation, resulting in the release of mediators of immediate hypersensitivity. These mediators rapidly induce both local gastrointestinal and systemic physiological responses including anaphylaxis. Emerging evidence has revealed that, in addition to inciting immediate reactions, mast cells are key regulators of adaptive immunity to foods. In the gastrointestinal mucosa they provide the priming cytokines that initiate and, over time, consolidate adaptive T_H2 responses to ingested allergens as well as TNF and chemokines that orchestrate the recruitment of tissue-infiltrating leukocytes that drive type 2 tissue inflammation. Patients with atopic dermatitis have increased intestinal mast cell numbers and are at a greater risk for food allergy. Recent studies have uncovered a skin-gut axis in which epicutaneous allergen exposure drives intestinal mast cell expansion. The activating effects of IgE antibodies in mast cells are countered by food-specific IgG antibodies that signal via the inhibitory IgG receptor, FcγR2b, suppressing both immediate allergic reactions to foods and the type 2 immune adjuvant activity of mast cells.

T-cell epitope discovery and single-cell technologies to advance food allergy research

There is good evidence for a role of T cells in food allergy, but there is a lack of mechanistic understanding and phenotypic markers of the specific T cells contributing to pathology. Recent technologic advancements have allowed for a new experimental paradigm where we can find and pull out rare antigen-specific T cells and characterize them at the single-cell level. However, studies in infectious disease and broader allergy have shown that these techniques benefit greatly from precisely defined T-cell epitopes. Food allergens have fewer epitopes currently available, but it is growing and promises to overcome this gap. With growing use of this experimental design, it will be important to unbiasedly map T-cell phenotypes across food allergy and look for commonalities and contrasts to other allergic and infectious diseases. Once a pathologic phenotype for T cells has been established, the frequencies of these cells can be monitored with simpler techniques that could be applied to the clinic and used in diagnosis, prediction of treatment responsiveness, and discovery of targets for new treatments.

Immune Responses at Host Barriers and Their Importance in Systemic Autoimmune Diseases

Host barriers such as the skin, the lung mucosa, the intestinal mucosa and the oral cavity are crucial at preventing contact with potential threats and are populated by a diverse population of innate and adaptive immune cells. Alterations in antigen recognition driven by genetic and environmental factors can lead to autoimmune systemic diseases such rheumatoid arthritis, systemic lupus erythematosus and food allergy. Here we review how different immune cells residing at epithelial barriers, host-derived signals and environmental signals are involved in the initiation and progression of autoimmune responses in these diseases. We discuss how regulation of innate responses at these barriers and the influence of environmental factors such as the microbiota can affect the susceptibility to develop local and systemic autoimmune responses particularly in the cases of food allergy, systemic lupus erythematosus and rheumatoid arthritis. Induction of pathogenic autoreactive immune responses at host barriers in these diseases can contribute to the initiation and progression of their pathogenesis.

Effects of Avenanthramide on the Small Intestinal Damage through Hsp70-NF-κB Signaling in an Ovalbumin-Induced Food Allergy Model

A food allergy is caused by an abnormal immune reaction and can induce serious intestinal inflammation and tissue damage. Currently, the avoidance of food allergens is still the most effective way to prevent or reduce allergic symptoms, so the development of new strategies to treat allergies is important. Avenanthramide (AVA) is a bioactive polyphenol derived from oats with a wide range of biological activities; however, it is still not clear whether or how AVA alleviates intestinal damage under allergic situations. The aim of this study was to explore the effect of AVA on the small intestinal damage in an ovalbumin (OVA)-induced food allergy model and its mechanism. In experiment 1, 10 mg/kg bw and 20 mg/kg bw doses of AVA both decreased the serum levels of OVA-specific IgE, histamine, and prostaglandin D induced by OVA. The AVA administration relieved inflammation indicated by the lower serum concentrations of pro-inflammatory cytokines including interleukin-1β, IL-6, and tumor necrosis factor-α. The levels of tight junction proteins including Claudin-1, ZO-1, and Occludin in the jejunum were elevated after AVA administration, accompanied by the improved intestinal morphology. Furthermore, AVA elevated the protein expression of heat shock protein 70 (Hsp70) and inhibited the phosphorylation of nuclear factor kappa-B (NF-κB), thus the apoptozole, which a Hsp70 inhibitor, was applied in experiment 2 to assess the contribution of Hsp70-NF-κB signaling to the effects of AVA. In the experiment 2, the inhibition of Hsp70 signaling treatment abolished the beneficial effects of AVA on the small intestinal damage and other allergic symptoms in mice challenged with OVA. Taken together, our results indicated that AVA exerted an intestinal protection role in the OVA-induced allergy, the mechanism of which was partly mediated by the Hsp70-NF-κB signaling.

Dietary antigens suppress the proliferation of type 2 innate lymphoid cells by restraining homeostatic IL-25 production

Dietary antigens affect the adaptive immunity of the host by inducing regulatory T cells and IgE-producing B cells. However, their roles in innate immune compartments such as innate lymphoid cells (ILCs) and intestinal epithelial cells (IECs) are unclear. Here, using antigen-free (AF) mice, which are germ-free (GF) mice fed with amino-acid-based diet, we found dietary proteins suppress the development of GATA-3-expressing ILC2s independent of the adaptive immune cells. These cells produce more type 2 cytokines and upregulated proliferation and activation markers such as Ki-67, CD69, and CD25. With this, AF mice had increased expressions of tuft cell-specific transcripts such as Il25, Il33, Dclk1, Trpm5, and Pou2f3 in IECs. Accordingly, expanded ILC2s upregulated IL-17RB, a receptor of IL-25, and their proliferation was blocked by IL-25 neutralizing or IL-17RB blocking antibodies. These results suggest a new dialogue between dietary antigens, IECs, and ILCs in which dietary antigens suppress ILC2 activation and proliferation by restraining homeostatic IL-25 production, potentially limiting type 2 immunity by food antigens.

Neuro-immune crosstalk and food allergy: Focus on enteric neurons and mucosal mast cells

The nervous system and the immune system individually play important roles in regulating the processes necessary to maintain physiological homeostasis, respond to acute stress and protect against external threats. These two regulating systems for maintaining the living body had often been assumed to function independently. Allergies develop as a result of an overreaction of the immune system to substances that are relatively harmless to the body, such as food, pollen and dust mites. Therefore, it has been generally supposed that the development and pathogenesis of allergies can be explained through an immunological interpretation. Recently, however, neuro-immune crosstalk has attracted increasing attention. Consequently, it is becoming clear that there is close morphological proximity and physiological and pathophysiological interactions between neurons and immune cells in various peripheral tissues. Thus, researchers are now beginning to appreciate that neuro-immune interactions may play a role in tissue homeostasis and the pathophysiology of immune-mediated disease, but very little information is available on the molecular basis of these interactions. Mast cells are a part of the innate immune system implicated in allergic reactions and the regulation of host-pathogen interactions. Mast cells are ubiquitous in the body, and these cells are often found in close proximity to nerve fibers in various tissues, including the lamina propria of the intestine. Mast cells and neurons are thought to communicate bidirectionally to modulate neurophysiological effects and mast cell functions, which suggests that neuro-immune interactions may be involved in the pathology of allergic diseases.

A new method to reduce allergenicity by improving the functional properties of soybean 7S protein through covalent modification with polyphenols

The 7S fraction contains several major allergens of soybean protein. Here, the effects of covalent modification by chlorogenic acid (CHA) and (-)-epigallo-catechin 3-gallate (EGCG) on the allergenicity and functional properties of soybean 7S protein were investigated. Conjugation with EGCG and CHA resulted in the formation of cross-linked protein polymers and changes to the structures of the protein, which might mask or destroy the epitopes on it. In vitro analysis revealed that modification by polyphenols noticeably reduced IgE binding activity and histamine release. In vivo analysis showed that modification led to milder anaphylactic shock symptoms and minor damage of the intestine in mice, with reducing IgG, IgE, IgG1, mMCP-1, and histamine levels. The allergic response was also suppressed by the repression of IFN-γ, IL-4, and IL-5 and the up-regulation of IL-10 and TGF-β in the conjugate groups. Furthermore, modification enhanced antioxidant, emulsion, foaming capacity, and foam stability of the protein.

Homeostatic serum IgE is secreted by plasma cells in the thymus and enhances mast cell survival

Increased serum levels of immunoglobulin E (IgE) is a risk factor for various diseases, including allergy and anaphylaxis. However, the source and ontogeny of B cells producing IgE under steady state conditions are not well defined. Here, we show plasma cells that develop in the thymus and potently secrete IgE and other immunoglobulins, including IgM, IgA, and IgG. The development of these IgE-secreting plasma cells are induced by IL-4 produced by invariant Natural Killer T cells, independent of CD1d-mediated interaction. Single-cell transcriptomics suggest the developmental landscape of thymic B cells, and the thymus supports development of transitional, mature, and memory B cells in addition to plasma cells. Furthermore, thymic plasma cells produce polyclonal antibodies without somatic hypermutation, indicating they develop via the extra-follicular pathway. Physiologically, thymic-derived IgEs increase the number of mast cells in the gut and skin, which correlates with the severity of anaphylaxis. Collectively, we define the ontogeny of thymic plasma cells and show that steady state thymus-derived IgEs regulate mast cell homeostasis, opening up new avenues for studying the genetic causes of allergic disorders.

Elevated levels of IgE is associated with a range of allergic pathology but the source of such IgE producing B cells during the steady state is poorly understood. Here, Kwon et al. show that homeostatic IgE is secreted by plasma cells in the thymus and link this to mast cell survival.

Reducing the Allergenicity of Shrimp Tropomyosin and Allergy Desensitization Based on Glycation Modification

Shrimp is a major allergic food that could trigger severe food allergy, with the most significant and potent allergen of shrimp referred to as tropomyosin (TM). Glycation modification (Maillard reaction) could reportedly weaken the allergenicity of TM and generate hypoallergenic TM, while up to now, there is still a lack of investigations on the hypoallergenic glycated tropomyosin (GTM) as a candidate immunotherapy for desensitizing the shrimp TM-induced allergy. This study analyzed the effects of glycation modification on decreasing the allergenicity of TM and generated hypoallergenic GTM and how GTM absorbed to the Al(OH)₃ function as a candidate immunotherapy for desensitizing allergy. As the results, in comparison to TM, the saccharides of smaller molecular sizes could lead to more advanced glycation end products in GTMs than saccharides of greater molecular sizes, and TM glycated by saccharides of different molecular sizes (glucose, maltose, maltotriose, maltopentaose, and maltoheptaose) exhibited lower allergenicity as a hypoallergen upon activating the allergic reactions of the mast cell and mouse model, while TM glycated by maltose had insignificant allergenicity changes upon activating the allergic reactions of the mast cell and mouse model. In addition, the hypoallergenic GTM + Al(OH)₃ was efficient as a candidate immunotherapy; this work intended to offer preclinical data to promote GTM + Al(OH)₃ as a candidate allergen-specific immunotherapy for desensitizing the allergy reactions for patients allergic to shrimp food.

Tissue-Specific Molecular Markers and Heterogeneity in Type 2 Innate Lymphoid Cells

Innate lymphoid cells (ILCs) are the most recently described group of lymphoid subpopulations. These tissue-resident cells display a heterogeneity resembling that observed on different groups of T cells, hence their categorization as cytotoxic NK cells and helper ILCs type 1, 2 and 3. Each one of these groups is highly diverse and expresses different markers in a context-dependent manner. Type 2 innate lymphoid cells (ILC2s) are activated in response to helminth parasites and regulate the immune response. They are involved in the etiology of diseases associated with allergic responses as well as in the maintenance of tissue homeostasis. Markers associated with their identification differ depending on the tissue and model used, making the study and understanding of these cells a cumbersome task. This review compiles evidence for the heterogeneity of ILC2s as well as discussion and analyses of molecular markers associated with their identity, function, tissue-dependent expression, and how these markers contribute to the interaction of ILC2s with specific microenvironments to maintain homeostasis or respond to pathogenic challenges.

Pathogenesis of IgE-mediated food allergy and implications for future immunotherapeutics

Our understanding of the immune basis of food allergy has grown rapidly in parallel with the development of new immune-targeted interventions for the treatment of food allergy. Local tissue factors, including the composition of skin and gastrointestinal microbiota and production of Th2-inducing cytokines (TSLP, IL-33, and IL-25) from barrier sites, have been shown not only to contribute to the development of food allergy, but also to act as effective targets for treatment in mice. Ongoing clinical trials are testing the targeting of these factors in human disease. There is a growing understanding of the contribution of IL-13 to the induction of high-affinity IgE and the need for continual T-cell help in the maintenance of long-lived IgE. This provides a strong rationale to test biologics targeting both IL-4 and IL-13 in the treatment of established food allergy. Various forms of allergen immunotherapy for food allergy have clearly shown that low specific IgE and elevated specific IgG4 are predictive of sustained treatment effect. Treatments that mimic that immune response, for example, lowering IgE, with monoclonal antibodies such as omalizumab, or administering allergen-specific IgG, are in various stages of investigation. As we gain more opportunities to use immune-modifying treatments for the treatment of food allergy, studies of the immune and clinical response to those interventions will continue to rapidly advance our understanding of the immune basis of food allergy and tolerance.

Innate lymphoid cells: The missing part of a puzzle in food allergy

Food allergy is an increasingly prevalent disease driven by uncontrolled type 2 immune response. Currently, knowledge about the underlying mechanisms that initiate and promote the immune response to dietary allergens is limited. Patients with food allergy are commonly sensitized through the skin in their early life, later on developing allergy symptoms within the gastrointestinal tract. Food allergy results from a dysregulated type 2 response to food allergens, characterized by enhanced levels of IgE, IL-4, IL-5, and IL-13 with infiltration of mast cells, eosinophils, and basophils. Recent studies raised a possible role for the involvement of innate lymphoid cells (ILCs) in driving food allergy. Unlike lymphocytes, ILCs lack They represent a group of lymphocytes that lack specific antigen receptors. ILCs contribute to immune responses not only by releasing cytokines and other mediators but also by responding to cytokines produced by activated cells in their local microenvironment. Due to their localization at barrier surfaces of the airways, gut, and skin, ILCs form a link between the innate and adaptive immunity. This review summarizes recent evidence on how skin and gastrointestinal mucosal immune system contribute to both homeostasis and the development of food allergy, as well as the involvement of ILCs toward inflammatory processes and regulatory mechanisms.

The Role of Type 2 Innate Lymphoid Cells in Allergic Diseases

Allergic diseases are significant diseases that affect many patients worldwide. In the past few decades, the incidence of allergic diseases has increased significantly due to environmental changes and social development, which has posed a substantial public health burden and even led to premature death. The understanding of the mechanism underlying allergic diseases has been substantially advanced, and the occurrence of allergic diseases and changes in the immune system state are known to be correlated. With the identification and in-depth understanding of innate lymphoid cells, researchers have gradually revealed that type 2 innate lymphoid cells (ILC2s) play important roles in many allergic diseases. However, our current studies of ILC2s are limited, and their status in allergic diseases remains unclear. This article provides an overview of the common phenotypes and activation pathways of ILC2s in different allergic diseases as well as potential research directions to improve the understanding of their roles in different allergic diseases and ultimately find new treatments for these diseases.

Evolution of our view on the IgE molecule role in bronchial asthma and the clinical effect of its modulation by omalizumab: Where do we stand today?

Bronchial asthma is a heterogeneous disease whose definition and treatment are based on evidence of variable airway obstruction and airway inflammation. Despite the enormous increase in the amount of information on the pathogenesis of this disease, diagnosis is still an unresolved problem, as we still lack sensitive and specific biomarkers. On the other hand, at the turn of the 20th and 21st century, there was a rapid development of therapeutic modalities based on the principle of biological therapy. The first authorized drug matching these characteristics was omalizumab – a monoclonal antibody directed against immunoglobulin E (IgE). It has been used for the treatment of severe forms of bronchial asthma for more than 15 years, which is a sufficient time to acquire ways of its effective use and to assess whether the treatment with omalizumab has met our expectations. However, we continue to discover new and surprising facts about the effects of omalizumab treatment which leads to widening of therapeutic indications. In this work, a basic overview of the very complex role of the IgE molecule in the organism (with a special emphasis on allergic asthma) is discussed, and the most important practical and clinical consequences resulting from its modulation by targeted therapy with omalizumab are summarized.

Reducing the Allergenicity of α-Lactalbumin after Lipid Peroxidation

This study analyzed the effect of lipid peroxidation using 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH) and acrolein on the in vitro and in vivo allergenicity of α-lactalbumin (α-La). The structure of oxidized α-La was evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, fluorescence spectroscopy, and circular dichroism, whereas the changes in the allergenic properties were evaluated. Lipid peroxidation induced changes to the structural properties that might destroy and/or mask α-La epitopes. In comparison to native α-La, oxidation complexes caused a decrease in the immunoglobulin E (IgE) binding capacity, as observed via immunoblotting. Moreover, the capacity to release mediators and cytokines from KU812 cells was also greatly reduced. In vivo, oxidation with AAPH and acrolein caused a significant reduction in IgE, IgG, IgG1, mast cell protease 1, and plasma histamine, along with the reduction of mast surface c-Kit⁺ and FcεRI⁺ expression. Therefore, these results indicate that oxidation via AAPH and acrolein can potentially reduce the allergenicity of α-La, which can help with the better understanding of the changes in allergenicity of milk allergen by lipid peroxidation.

Group 2 Innate Lymphoid Cells: Team Players in Regulating Asthma

Type 2 immunity helps protect the host from infection, but it also plays key roles in tissue homeostasis, metabolism, and repair. Unfortunately, inappropriate type 2 immune reactions may lead to allergy and asthma. Group 2 innate lymphoid cells (ILC2s) in the lungs respond rapidly to local environmental cues, such as the release of epithelium-derived type 2 initiator cytokines/alarmins, producing type 2 effector cytokines such as IL-4, IL-5, and IL-13 in response to tissue damage and infection. ILC2s are associated with the severity of allergic asthma, and experimental models of lung inflammation have shown how they act as playmakers, receiving signals variously from stromal and immune cells as well as the nervous system and then distributing cytokine cues to elicit type 2 immune effector functions and potentiate CD4⁺ T helper cell activation, both of which characterize the pathology of allergic asthma. Recent breakthroughs identifying stromal- and neuronal-derived microenvironmental cues that regulate ILC2s, along with studies recognizing the potential plasticity of ILC2s, have improved our understanding of the immunoregulation of asthma and opened new avenues for drug discovery.

Investigation of glycated shrimp tropomyosin as a hypoallergen for potential immunotherapy

Tropomyosin (TM) is the most important allergen in shrimps that could cause food allergy. Glycation is reported to be effective in reducing TM allergenicity and produce hypoallergen; however, up to now, there are very few reports on the potential of hypoallergenic glycated TM (GTM) as allergen immunotherapy for shrimp TM-induced food allergy. This study investigated the glycation of TM-produced hypoallergen and the immunotherapeutic efficacy of GTM + Al(OH)₃ as potential allergen immunotherapy. Compared to TM, the TM glycated by glucose (TM-G), maltotriose (TM-MTS), maltopentaose (TM-MPS) and maltoheptaose (TM-MHS) had weaker allergy activation on mast cells and mouse model as a hypoallergen. However, the TM glycated by maltose (TM-M) insignificantly affected the allergenicity. In addition, the GTM absorbed into Al(OH)₃ could be efficacious as potential allergen immunotherapy, particularly for the TM glycated by the saccharides having larger molecular size (e.g., TM-MHS), which could provide preclinical data to develop GTM + Al(OH)₃ as a candidate immunotherapy for shrimp allergic patients.

Stem Cell Factor Neutralization Protects From Severe Anaphylaxis in a Murine Model of Food Allergy

Food allergy is a growing public health problem with ~15 million people affected in the United States. In allergic food disease, IgE on mast cells bind to ingested antigens leading to the activation and degranulation of mast cells. Stem cell factor (SCF) is mast cell growth and activation factor that is required for peripheral tissue mast cells. We targeted a specific isoform of SCF, the larger 248 amino acid form, that drives peripheral tissue mast cell differentiation using a specific monoclonal antibody in a model of food allergy. Ovalbumin sensitized and intragastrically challenged mice were monitored for symptoms of anaphylaxis including respiratory distress, diarrhea, and a reduction in body temperature. During the second week of challenges, allergic mice were injected with an antibody to block SCF248 or given IgG control. Mice treated with α-SCF248 had a decreased incidence of diarrhea and no reduction in body temperature suggesting a reduction in anaphylaxis compared to IgG control treated animals. Re-stimulated mesenteric lymph nodes indicated that α-SCF248 treated mice had decreased OVA-specific Th2 cytokine production compared to IgG control treated allergic animals. The reduction of food induced anaphylaxis was accompanied by a significant reduction in gut leak. The mesenteric lymph node cells were analyzed by flow cytometry and showed a decrease in the number of type 2 innate lymphoid cells in mice injected with α-SCF248. Morphometric enumeration of esterase+ mast cells demonstrated a significant reduction throughout the small intestine. Using a more chronic model of persistent food-induced anaphylaxis, short term therapeutic treatment with α-SCF248 during established disease effectively blocked food induced anaphylaxis. Together, these data suggest that therapeutically blocking SCF248 in food allergic animals can reduce the severity of food allergy by reducing mast cell mediated disease activation.

miR103a-3p in extracellular vesicles from FcεRI-aggregated human mast cells enhances IL-5 production by group 2 innate lymphoid cells

BACKGROUND

Mast cells (MCs) are key regulators of IgE-mediated allergic inflammation. Cell-derived extracellular vesicles (EVs) contain bioactive compounds such as microRNAs. EVs can transfer signals to recipient cells, thus using a novel mechanism of cell-to-cell communication. However, whether MC-derived EVs are involved in FcεRI-mediated allergic inflammation is unclear.

OBJECTIVE

We sought to investigate the effect of EVs derived from FcεRI-aggregated human MCs on the function of human group 2 innate lymphoid cells (ILC2s).

METHODS

Human cultured MCs were sensitized with and without IgE for 1 hour and then incubated with anti-IgE antibody, IL-33, or medium alone for 24 hours. EVs in the MC supernatant were isolated by using ExoQuick-TC.

RESULTS

Coculture of ILC2s with EVs derived from the FcεRI-aggregated MCs significantly enhanced IL-5 production and sustained upregulation of IL-5 mRNA expression in IL-33-stimulated ILC2s, but IL-13 production and IL-13 mRNA expression were unchanged. miR103a-3p expression was upregulated in IL-33-stimulated ILC2s that had been cocultured with EVs derived from anti-IgE antibody-stimulated MCs. Transduction of an miR103a-3p mimic to ILC2s significantly enhanced IL-5 production by IL-33-stimulated ILC2s. miR103a-3p promoted demethylation of an arginine residue of GATA3 by downregulating protein arginine methyltransferase 5 (PRMT5) mRNA. Reduction of protein arginine methyltransferase 5 expression in ILC2s by using a small interfering RNA technique resulted in upregulation of IL-5 production by IL-33-stimulated ILC2s. Furthermore, the level of miR103a-3p expression was significantly higher in EVs from sera of patients with atopic dermatitis than in EVs from nonatopic healthy control subjects.

CONCLUSION

Eosinophilic allergic inflammation may be exacerbated owing to ILC2 activation by MC-derived miR103a-3p.

Mechanisms Underlying the Skin-Gut Cross Talk in the Development of IgE-Mediated Food Allergy

Immune-globulin E (IgE)-mediated food allergy is characterized by a variety of clinical entities within the gastrointestinal tract, skin and lungs, and systemically as anaphylaxis. The default response to food antigens, which is antigen specific immune tolerance, requires exposure to the antigen and is already initiated during pregnancy. After birth, tolerance is mostly acquired in the gut after oral ingestion of dietary proteins, whilst exposure to these same proteins via the skin, especially when it is inflamed and has a disrupted barrier, can lead to allergic sensitization. The crosstalk between the skin and the gut, which is involved in the induction of food allergy, is still incompletely understood. In this review, we will focus on mechanisms underlying allergic sensitization (to food antigens) via the skin, leading to gastrointestinal inflammation, and the development of IgE-mediated food allergy. Better understanding of these processes will eventually help to develop new preventive and therapeutic strategies in children.

IgE and IgG Antibodies as Regulators of Mast Cell and Basophil Functions in Food Allergy

Food allergy is a major health issue, affecting the lives of 8% of U.S. children and their families. There is an urgent need to identify the environmental and endogenous signals that induce and sustain allergic responses to ingested allergens. Acute reactions to foods are triggered by the activation of mast cells and basophils, both of which release inflammatory mediators that lead to a range of clinical manifestations, including gastrointestinal, cutaneous, and respiratory reactions as well as systemic anaphylaxis. Both of these innate effector cell types express the high affinity IgE receptor, FcϵRI, on their surface and are armed for adaptive antigen recognition by very-tightly bound IgE antibodies which, when cross-linked by polyvalent allergen, trigger degranulation. These cells also express inhibitory receptors, including the IgG Fc receptor, FcγRIIb, that suppress their IgE-mediated activation. Recent studies have shown that natural resolution of food allergies is associated with increasing food-specific IgG levels. Furthermore, oral immunotherapy, the sequential administration of incrementally increasing doses of food allergen, is accompanied by the strong induction of allergen-specific IgG antibodies in both human subjects and murine models. These can deliver inhibitory signals via FcγRIIb that block IgE-induced immediate food reactions. In addition to their role in mediating immediate hypersensitivity reactions, mast cells and basophils serve separate but critical functions as adjuvants for type 2 immunity in food allergy. Mast cells and basophils, activated by IgE, are key sources of IL-4 that tilts the immune balance away from tolerance and towards type 2 immunity by promoting the induction of Th2 cells along with the innate effectors of type 2 immunity, ILC2s, while suppressing the development of regulatory T cells and driving their subversion to a pathogenic pro-Th2 phenotype. This adjuvant effect of mast cells and basophils is suppressed when inhibitory signals are delivered by IgG antibodies signaling via FcγRIIb. This review summarizes current understanding of the immunoregulatory effects of mast cells and basophils and how these functions are modulated by IgE and IgG antibodies. Understanding these pathways could provide important insights into innovative strategies for preventing and/or reversing food allergy in patients.

IgE and mast cells: The endogenous adjuvant

Mast cells and IgE are most familiar as the effectors of type I hypersensitivity reactions including anaphylaxis. It is becoming clear however that this pair has important immunomodulatory effects on innate and adaptive cells of the immune system. In this purview, they act as endogenous adjuvants to ignite evolving immune responses, promote the transition of allergic disease into chronic illness and disrupt the development of active mechanisms of tolerance to ingested foods. Suppression of IgE-mediated mast cell activation can be exerted by molecules targeting IgE, FcɛRI or signaling kinases including Syk, or by IgG antibodies acting via inhibitory Fcγ receptors. In 2015 we reviewed the evidence for the adjuvant functions of mast cells. This update includes the original text, incorporates some important developments in the field over the past five years and discusses how interventions targeting these pathways might have promise in the development of strategies to treat allergic disease.

Functional Inactivation of Mast Cells Enhances Subcutaneous Adipose Tissue Browning in Mice

Adipose tissue browning and systemic energy expenditure provide a defense mechanism against obesity and associated metabolic diseases. In high-cholesterol Western diet-fed mice, mast cell (MC) inactivation ameliorates obesity and insulin resistance and improves the metabolic rate, but a direct role of adipose tissue MCs in thermogenesis and browning remains unproven. Here, we report that adrenoceptor agonist norepinephrine-stimulated metabolic rate and subcutaneous adipose tissue (SAT) browning are enhanced in MC-deficient Kit^w-sh/w-sh mice and MC-stabilized wild-type mice on a chow diet. MC reconstitution to SAT in Kit^w-sh/w-sh mice blocks these changes. Mechanistic studies demonstrate that MC inactivation elevates SAT platelet-derived growth factor receptor A (PDGFRα⁺) adipocyte precursor proliferation and accelerates beige adipocyte differentiation. Using the tryptophan hydroxylase 1 (TPH1) inhibitor and TPH1-deficient MCs, we show that MC-derived serotonin inhibits SAT browning and systemic energy expenditure. Functional inactivation of MCs or inhibition of MC serotonin synthesis in SAT promotes adipocyte browning and systemic energy metabolism in mice.

Immunomodulatory Effect of Laccase/Caffeic Acid and Transglutaminase in Alleviating Shrimp Tropomyosin (Met e 1) Allergenicity

This work aimed to investigate the effect of enzymatic cross-linking on the allergenic potential of shrimp tropomyosin (TM), Met e 1. The cross-linked TM with laccase (CL), laccase/caffeic acid (CLC and CLC⁺), and transglutaminase (CTG and CTG⁺) formed macromolecules and altered the allergen conformation. The IgG/IgE-binding potentials of the cross-linked TM were reduced as confirmed by Western blotting and ELISA. Enzymatic cross-linking improved the gastrointestinal digestibility and induced a lower level of degranulation in RBL-2H3 and KU812 cells. Moreover, cross-linked TM decreased anaphylactic symptoms, as well as reduced the serum levels of IgG1, IgE, histamine, tryptase, and mMCP-1. In spleen cells, CLC⁺ and CTG⁺ downregulated the Th2-related cytokines and upregulated IFN-γ and IL-10. These findings revealed that CTG⁺ has shown more potential than CLC⁺ in mitigating the allergenicity of TM by influencing the conformational structure, enhancing the digestibility, decreasing the cellular degranulation process, and positively modulating the Th1/Th2 immunobalance.

Changes in Allergenicity of Ovalbumin in Vitro and in Vivo on Conjugation with Quercetin

A previous study demonstrated decreased allergenicity in vitro of some food allergens after conjugation with polyphenols. However, little is known about how polyphenol conjugation with food allergens affects in vivo allergenicity. We conjugated a well-known food allergen, ovalbumin (OVA), with quercetin (QUE) to assess the potential allergenicity of OVA in vitro and in vivo in a BALB/c mouse model. QUE could covalently conjugate with OVA and changed the protein structure, which might destroy and/or mask OVA epitopes. Conjugation with QUE decreased IgE binding properties and the release capacity of the conjugated OVA. In vivo, as compared with native protein, conjugation with QUE decreased the levels of IgE, IgG1, IgG, plasma histamine, and mast cell protease-1 (mMCP-1) on the surface of sensitized mast cells, along with decreased FcεRI⁺ and c-kit⁺ expression. The levels of Th2-related cytokines (IL-4, IL-5, IL-13) decreased and that of a Th1-related cytokine (IFN-γ) increased slightly, which suggests that conjugation with QUE modulated the imbalance of the Th1/Th2 immune response. Conjugation of OVA with QUE could reduce OVA allergenicity in vitro and in vivo, which could provide information for reducing food allergenicity by conjugation with polyphenols.