Association of STAT6 gene variants with food allergy diagnosed by double-blind placebo-controlled food challenges

Identification of the biological processes, immune cell landscape, and hub genes shared by acute anaphylaxis and ST-segment elevation myocardial infarction

Background: Patients with anaphylaxis are at risk for ST-segment elevation myocardial infarction (STEMI). However, the pathological links between anaphylaxis and STEMI remain unclear. Here, we aimed to explore shared biological processes, immune effector cells, and hub genes of anaphylaxis and STEMI. Methods: Gene expression data for anaphylactic (GSE69063) and STEMI (GSE60993) patients with corresponding healthy controls were pooled from the Gene Expression Omnibus database. Differential expression analysis, enrichment analysis, and CIBERSORT were used to reveal transcriptomic signatures and immune infiltration profiles of anaphylaxis and STEMI, respectively. Based on common differentially expressed genes (DEGs), Gene Ontology analysis, cytoHubba algorithms, and correlation analyses were performed to identify biological processes, hub genes, and hub gene-related immune cells shared by anaphylaxis and STEMI. The robustness of hub genes was assessed in external anaphylactic (GSE47655) and STEMI (GSE61144) datasets. Furthermore, a murine model of anaphylaxis complicated STEMI was established to verify hub gene expressions. The logistic regression analysis was used to evaluate the diagnostic efficiency of hub genes. Results: 265 anaphylaxis-related DEGs were identified, which were associated with immune-inflammatory responses. 237 STEMI-related DEGs were screened, which were involved in innate immune response and myeloid leukocyte activation. M0 macrophages and dendritic cells were markedly higher in both anaphylactic and STEMI samples compared with healthy controls, while CD4⁺ naïve T cells and CD8⁺ T cells were significantly lower. Enrichment analysis of 33 common DEGs illustrated shared biological processes of anaphylaxis and STEMI, including cytokine-mediated signaling pathway, response to reactive oxygen species, and positive regulation of defense response. Six hub genes were identified, and their expression levels were positively correlated with M0 macrophage abundance and negatively correlated with CD4⁺ naïve T cell abundance. In external anaphylactic and STEMI samples, five hub genes (IL1R2, FOS, MMP9, DUSP1, CLEC4D) were confirmed to be markedly upregulated. Moreover, experimentally induced anaphylactic mice developed impaired heart function featuring STEMI and significantly increased expression of the five hub genes. DUSP1 and CLEC4D were screened as blood diagnostic biomarkers of anaphylaxis and STEMI based on the logistic regression analysis. Conclusion: Anaphylaxis and STEMI share the biological processes of inflammation and defense responses. Macrophages, dendritic cells, CD8⁺ T cells, and CD4⁺ naïve T cells constitute an immune cell population that acts in both anaphylaxis and STEMI. Hub genes (DUSP1 and CLEC4D) identified here provide candidate genes for diagnosis, prognosis, and therapeutic targeting of STEMI in anaphylactic patients.

Multi-omics profiling approach in food allergy

The prevalence of food allergy (FA) among children is increasing, affecting nearly 8% of children, and FA is the most common cause of anaphylaxis and anaphylaxis-related emergency department visits in children. Importantly, FA is a complex, multi-system, multifactorial disease mediated by food-specific immunoglobulin E (IgE) and type 2 immune responses and involving environmental and genetic factors and gene-environment interactions. Early exposure to external and internal environmental factors largely influences the development of immune responses to allergens. Genetic factors and gene-environment interactions have established roles in the FA pathophysiology. To improve diagnosis and identification of FA therapeutic targets, high-throughput omics approaches have emerged and been applied over the past decades to screen for potential FA biomarkers, such as genes, transcripts, proteins, and metabolites. In this article, we provide an overview of the current status of FA omics studies, namely genomic, transcriptomic, epigenomic, proteomic, exposomic, and metabolomic. The current development of multi-omics integration of FA studies is also briefly discussed. As individual omics technologies only provide limited information on the multi-system biological processes of FA, integration of population-based multi-omics data and clinical data may lead to robust biomarker discovery that could translate into advances in disease management and clinical care and ultimately lead to precision medicine approaches.

Advances and potential of omics studies for understanding the development of food allergy

The prevalence of food allergy continues to rise globally, carrying with it substantial safety, economic, and emotional burdens. Although preventative strategies do exist, the heterogeneity of allergy trajectories and clinical phenotypes has made it difficult to identify patients who would benefit from these strategies. Therefore, further studies investigating the molecular mechanisms that differentiate these trajectories are needed. Large-scale omics studies have identified key insights into the molecular mechanisms for many different diseases, however the application of these technologies to uncover the drivers of food allergy development is in its infancy. Here we review the use of omics approaches in food allergy and highlight key gaps in knowledge for applying these technologies for the characterization of food allergy development.

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.

Food allergy across the globe

The prevalence of food allergy (FA) is increasing in some areas of the globe, highlighting the need for better strategies for prevention, diagnosis, and therapy. In the last few decades, we have made great strides in understanding the causes and mechanisms underlying FAs, prompting guideline updates. Earlier guidelines recommended avoidance of common food allergens during pregnancy and lactation and delaying the introduction of allergenic foods in children aged between 1 and 3 years. Recent guidelines for allergy prevention recommend consumption of a healthy and diverse diet without eliminating or increasing the consumption of allergenic foods during pregnancy or breast-feeding. Early introduction of allergenic foods is recommended by most guidelines for allergy prevention after a period of exclusive breast-feedng (6 months [World Health Organization] or 4 months [European Academy of Allergy and Clinical Immunology]). New diagnostics for FA have been developed with varied availability of these tests in different countries. Finally, the first oral immunotherapy drug for FA was approved by the US Food and Drug Administration and European Medicines Agency in 2020. In this review, we will address the global prevalence of FA, our current understanding of the causes of FA, and the latest guidelines for preventing, diagnosing, and treating FA. We will also discuss similarities and differences between FA guidelines.

Allergic manifestations in autoimmune gastrointestinal disorders

Allergic disorders target a young population, are increasing in both incidence and prevalence and are associated with significant disease burden. They result from the complex interplay between (epi)genetic and environmental factors, resulting in a Th2 inflammatory process targeting the epithelium of the respiratory tract (allergic rhinitis and asthma), skin (atopic dermatitis), and gastrointestinal tract (food allergy). Although the exact pathogenic mechanisms remain elusive, an altered immune system response in the gut is increasingly recognized as a relevant step. Allergic and gastrointestinal autoimmune disorders share several epidemiological, pathogenic and risk factors and several treatment modalities. Here we revise the current literature and show that allergic disorders are highly prevalent in gastrointestinal autoimmune diseases, including celiac disease, inflammatory bowel disease, autoimmune pancreatitis, and autoimmune cholangiopathies. No data are available for some autoimmune diseases, such as autoimmune gastritis and autoimmune enteropathy. To ensure the comprehensive care of patients with autoimmune gastrointestinal disorders, along with disease-specific factors, the presence of allergic disorders should be evaluated and treated when present, possibly targeting shared molecular pathways. Future studies are needed to define the exact pathogenic mechanisms underpinning the association between allergic and autoimmune diseases of the gastrointestinal tract.

Current insights into the genetics of food allergy

Food allergy (FA), a growing public health burden in the United States, and familial aggregation studies support strong roles for both genes and environment in FA risk. Deepening our understanding of the molecular and cellular mechanisms driving FAs is paramount to improving its prevention, diagnosis, and clinical management. In this review, we document lessons learned from the genetics of FA that have aided our understanding of these mechanisms. Although current genetic association studies suffer from low power, heterogeneity in definition of FA, and difficulty in our ability to truly disentangle FA from food sensitization (FS) and general atopy genetics, they reveal a set of genetic loci, genes, and variants that continue to implicate the importance of barrier and immune function genes across the atopic march, and FA in particular. The largest reported effects on FA are from MALT1 (odds ratio, 10.99), FLG (average odds ratio, ∼2.9), and HLA (average odds ratio, ∼2.03). The biggest challenge in the field of FA genetics is to elucidate the specific mechanism of action on FA risk and pathogenesis for these loci, and integrative approaches including genetics/genomics with transcriptomics, proteomics, and metabolomics will be critical next steps to translating these genetic insights into practice.

Precision medicine in cow's milk allergy

PURPOSE OF REVIEW

The aim of this review is to describe the role of precision medicine in the diagnosis, treatment, and monitoring of cow's milk allergy.

RECENT FINDINGS

The development of 'omics' sciences in the field of food allergy has led to a better understanding of the allergenicity of cow's milk proteins and significant advances in the knowledge of the pathogenesis and mechanisms of cow's milk allergy. Omics-based technologies allow the practitioner to better differentiate cow's milk allergy subtypes and to predict cow's milk allergy (CMA) persistence over time. Precision medicine extends the role of the oral food challenge, to determine the individual's threshold doses, and to establish tolerance to baked milk products. Other than symptom relief, dietary strategies are currently being investigated for the potential to induce tolerance. Oral immunotherapy offers a treatment option for patients with severe and persistent IgE-mediated CMA. Individual baseline-immune profiles may be predictive of cow's milk oral immunotherapy safety and efficacy.Patient data derived from current technology, in combination with the patient's history, can be translated into treatments targeted at patient-tailored interventions.

SUMMARY

The identification of novel biomarkers may improve diagnostic accuracy and also predict patient responsiveness to treatments. Integration of patient data will become increasingly important as omics technologies become more widely used in the clinical setting.

Recent developments and advances in atopic dermatitis and food allergy

This review highlights recent advances in atopic dermatitis (AD) and food allergy (FA), particularly on molecular mechanisms and disease endotypes, recent developments in global strategies for the management of patients, pipeline for future treatments, primary and secondary prevention and psychosocial aspects. During the recent years, there has been major advances in personalized/precision medicine linked to better understanding of disease pathophysiology and precision treatment options of AD. A greater understanding of the molecular and cellular mechanisms of AD through substantial progress in epidemiology, genetics, skin immunology and psychological aspects resulted in advancements in the precision management of AD. However, the implementation of precision medicine in the management of AD still requires the validation of reliable biomarkers, which will provide more tailored management, starting from prevention strategies towards targeted therapies for more severe diseases. Cutaneous exposure to food via defective barriers is an important route of sensitization to food allergens. Studies on the role of the skin barrier genes demonstrated their association with the development of IgE-mediated FA, and suggest novel prevention and treatment strategies for type 2 diseases in general because of their link to barrier defects not only in AD and FA, but also in asthma, chronic rhinosinusitis, allergic rhinitis and inflammatory bowel disease. The development of more accurate diagnostic tools, biomarkers for early prediction, and innovative solutions require a better understanding of molecular mechanisms and the pathophysiology of FA. Based on these developments, this review provides an overview of novel developments and advances in AD and FA, which are reported particularly during the last two years.

Likely questionnaire-diagnosed food allergy in 78, 890 adults from the northern Netherlands

BACKGROUND

It is challenging to define likely food allergy (FA) in large populations which limited the number of large studies regarding risk factors for FA.

OBJECTIVE

We studied the prevalence and characteristics of self-reported FA (s-rFA) in the large, population-based Dutch Lifelines cohort and identified associated risk factors.

METHODS

Likely food allergic cases (LikelyFA) were classified based on questionnaire reported characteristics consistent with FA. Subjects with atypical characteristics were classified as Indeterminate. We investigated 13 potential risk factors for LikelyFA such as birth mode and living on a farm and addressed health-related quality of life (H-RQOL).

RESULTS

Of the 78, 890 subjects, 12.1% had s-rFA of which 4.0% and 8.1% were classified as LikelyFA and Indeterminate, respectively. Younger age, female sex, asthma, eczema and nasal allergy increased the risk of LikelyFA (p-value range <1.00*10-250-1.29*10-7). Living in a small city/large village or suburb during childhood was associated with a higher risk of LikelyFA than living on a farm (p-value = 7.81*10-4 and p = 4.84*10-4, respectively). Subjects classified as Indeterminate more often reported depression and burn-out compared to those without FA (p-value = 1.46*10-4 and p = 8.39*10-13, respectively). No association was found with ethnicity, (duration of) breastfeeding, birth mode and reported eating disorder. Mental and physical component scores measuring H-RQOL were lower in both those classified as LikelyFA and Indeterminate compared to those without FA.

CONCLUSION

The prevalence of s-rFA among adults is considerable and one-third reports characteristics consistent with LikelyFA. Living on a farm decreased the risk of LikelyFA. The association of poorer H-RQOL as well as depression and burn-out with questionable self-perceived FA is striking and a priority for future study.

Association of the STAT6 rs3024974 (C/T) Polymorphism with IgE-Mediated Food Sensitization among West Bengal Population in India

INTRODUCTION

Genetic polymorphisms associated with IgE-mediated food sensitization have been a robust area of research for decades. A genome-wide search for susceptible loci regulating the IgE response (atopy) identified the candidate gene STAT6, which is important in the context of food allergic manifestations.

OBJECTIVE

The present study was designed to investigate the sensitization of West Bengal population against some common allergenic food items and to study the role of the STAT6 gene polymorphism in elevating food-specific IgE levels among sensitized individuals.

METHODS

Skin prick test was performed for 6 food items among 501 patients (126 children, 85 adolescents, and 290 adults)from West Bengal, India. Among them, 165 patients were selected for measurement of total IgE and food-specific IgE levels along with 165 controls. Finally, the STAT6 (rs3024974 (C/T) polymorphism was genotyped in 139 cases and control subjects.

RESULTS

Shrimp was identified as a dominant food allergen in adolescents and adults, whereas milk sensitization was highest in children. Food-sensitized patients with onset during childhood had significantly higher total IgE levels compared to patients with onset during adulthood (p < 0.00001). The frequency of the rs3024974 CC genotype in both cases and control subjects (55.40 and 46.76%, respectively) was higher than that of CT or TT. Patients with childhood onset bearing the CC genotype had significantly higher specific IgE levels in comparison to those with adult onset (p = 0.001).

CONCLUSION

Food sensitization has a genetic background and the rs3024974 polymorphism is associated with susceptibility and reaction severity in food-sensitized patients in West Bengal population in India.

Recent developments and highlights in immune monitoring of allergen immunotherapy

Allergic diseases are the most common chronic immune-mediated disorders and can manifest with an enormous diversity in clinical severity and symptoms. Underlying mechanisms for the adverse immune response to allergens and its downregulation by treatment are still being revealed. As a result, there have been, and still are, major challenges in diagnosis, prediction of disease progression/evolution and treatment. Currently, the only corrective treatment available is allergen immunotherapy (AIT). AIT modifies the immune response through long-term repeated exposure to defined doses of allergen. However, as the treatment usually needs to be continued for several years to be effective, and can be accompanied by adverse reactions, many patients face difficulties completing their schedule. Long-term therapy also potentially incurs high costs. Therefore, there is a great need for objective markers to predict or to monitor individual patient's beneficial changes in immune response during therapy so that efficacy can be identified as early as possible. In this review, we specifically address recent technical developments that have generated new insights into allergic disease pathogenesis, and how these could potentially be translated into routine laboratory assays for disease monitoring during AIT that are relatively inexpensive, robust and scalable.

Food and drug allergy, and anaphylaxis in EAACI journals (2018)

The European Academy of Allergy and Clinical Immunology (EAACI) supports three journals: "Allergy," "Pediatric Allergy and Immunology (PAI)," and "Clinical and Translational Allergy (CTA)." One of the major goals of EAACI is to support health promotion in which prevention of allergy and asthma plays a critical role and to disseminate the knowledge of allergy to all stakeholders including the EAACI junior members. This paper summarizes the achievements of 2018 in anaphylaxis, and food and drug allergy. Main topics that have been focused are anaphylaxis, mechanisms of food allergy (FA), epidemiology of FA, food allergens, diagnosis of FA, prevention and control of FA, FA immunotherapy, drug allergy, and political agenda.

The signal transducer and activator of transcription 6 (STAT-6) mediates Th2 inflammation and tissue damage in a murine model of peanut-induced food allergy

INTRODUCTION

Food allergies are inflammatory conditions mediated by Th2 and probably STAT-6 dependent immune responses.

OBJECTIVE AND DESIGN

Here we investigated the role of Signal Transducer and Activator of Transcription 6 (STAT-6) in development of inflammation in peanut allergy.

METHODS

To induce food allergy, wild-type (WT) and mice deficient for STAT-6 (Stat6^-/-) were sensitized with peanut proteins and challenged with peanut seeds.

RESULTS

WT animals lost weight and refused the peanut diet, in contrast to Stat6^-/- mice, which had a better maintenance of body weight and more regular seeds' consumption. The augmented peanut-specific IgG, IgG1 and IgE in the allergic WT was abolished in Stat6^-/- animals that also presented increased IgG2a. There was an overall reduction in the gut mediators in the absence of STAT-6, including those related to inflammatory and Th2 responses, in contrast to a rising counter regulatory and Th1 reaction in Stat-6^-/- mice. These animals had IFN-γ and IL-10 similar to WT after the four-week challenge. Most interestingly, Stat-6^-/- mice had no intestinal damage, in contrast to WT animals, which had inflammatory infiltrate, tissue destruction, epithelial exulceration, edema, congestion and loss of villous architecture in the small gut segments.

CONCLUSIONS

STAT-6 plays an important role in the establishment of the Th2 inflammatory responses and intestinal damage in peanut allergy.

CYP2C19 and STAT6 Variants Influence the Outcome of Proton Pump Inhibitor Therapy in Pediatric Eosinophilic Esophagitis

OBJECTIVE

Proton pump inhibitors (PPIs) are an effective treatment for eosinophilic esophagitis (EoE); however, only 30% to 60% of patients respond. Common genetic variants in CYP2C19 and STAT6 associate with PPI plasma concentration and magnitude of inflammatory response, respectively. Our objective was to determine if genetic variation in the genes for CYP2C19 and STAT6 influence differentiation between PPI responsive esophageal eosinophilia versus PPI nonresponsive EoE (PPI-REE, PPI-nonresponsive EoE).

METHODS

Genomic DNA was isolated from 92 esophageal tissue biopsies collected from participants of a prospective clinical trial of high-dose PPI therapy for esophageal eosinophilia in children.

RESULTS

Of the 92 patients examined, 57 (62%) were PPI-REE and 35 (38%) were PPI-nonresponsive EoE. Forty-six of the 92 patients were further characterized by pH probe monitoring; there was no association between reflux index and carriage of CYP2C1917 (P = 0.35). In children who received a PPI dose between ≥1.54 and ≤2.05 mg/kg/day, binary logistic regression modeling showed that carriage of CYP2C1917 associated with PPI-nonresponsive EoE (odds ratio (OR) [95% confidence interval (CI)] = 7.71 [1.21, 49.11], P = 0.031). Carriage of STAT6 allelic variant rs1059513 predicts PPI-REE (OR [95% CI] = 6.16 [1.44, 26.4], P = 0.028), whereas carriage of STAT6 rs324011 synergizes with CYP2C1917 to predict PPI-nonresponsive EoE (rs324011 OR [95% CI] = 5.56 [1.33, 20.72], P = 0.022; CYP2C1917 OR [95% CI] = 8.19[1.42, 50.57], P = 0.023).

CONCLUSIONS

Common variants in CYP2C19 and STAT6 associate with a PPI-nonresponsive EoE outcome of PPI therapy for esophageal eosinophilia suggesting that response rates may be improved by adopting a genotype-guided approach to PPI dosing.

Epithelial origin of eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic, allergen-driven inflammatory disease of the esophagus characterized predominantly by eosinophilic inflammation, leading to esophageal dysfunction. Converging data have placed the esophageal epithelium at the center of disease pathogenesis. In particular, the main EoE disease susceptibility loci at 2p23 and 5p22 encode for gene products that are produced by the esophageal epithelium: the intracellular protease calpain 14 and thymic stromal lymphopoietin, respectively. Furthermore, genetic and functional data establish a primary role for impaired epithelial barrier function in disease susceptibility and pathoetiology. Additionally, the EoE transcriptome, a set of genes dysregulated in the esophagi of patients with EoE, is enriched in genes that encode for proteins involved in esophageal epithelial cell differentiation. This transcriptome has a high proportion of esophagus-specific epithelial genes that are notable for the unexpected enrichment in genes encoding for proteases and protease inhibitors, as well as in IL-1 family genes, demonstrating a previously unappreciated role for innate immunity responses in the esophagus under homeostatic conditions. Among these pathways, basal production of the serine protease inhibitor, Kazal-type 7 (SPINK7) has been demonstrated to be part of the normal differentiation program of esophageal epithelium. Profound lost expression of SPINK7 occurs in patients with EoE and is sufficient for unleashing increased proteolytic activity (including urokinase plasminogen activator), impaired barrier function, and production of large quantities of proinflammatory and proallergic cytokines, including thymic stromal lymphopoietin. Collectively, we put forth a model in which the esophagus is normally equipped as an anti-inflammatory sensing organ and that defects in this pathway, mediated by epithelial protease/protease inhibitor imbalances, unleash inflammatory responses resulting in disorders, such as EoE.

Risk of Atopic Diseases among Siblings of Patients with Attention-Deficit Hyperactivity Disorder: A Nationwide Population-Based Cohort Study

BACKGROUND

Increasing evidence suggests a positive association between attention-deficit hyperactivity disorder (ADHD) and atopic diseases. However, the risk of atopic diseases in unaffected siblings of patients with ADHD has not been investigated.

OBJECTIVE

To investigate the risk of developing atopic diseases among unaffected siblings of ADHD probands.

METHODS

Using data from the Taiwan National Health Insurance Research Database, 20,170 unaffected siblings of patients with ADHD born between 1980 and 2000 and 80,680 age-, birth time-, and residence-matchedcontrols were included in this study. Diagnoses of atopic diseases, including asthma, atopic dermatitis, allergic rhinitis, and allergic conjunctivitis, were ascertained from 1996 or the birth time until the end of 2011.

RESULTS

Breslow-Cox proportional hazard regression analyses with adjustment for demographic data showed that compared with the controls, unaffected siblings of patients with ADHD had a higher risk of developing asthma (relative risk [RR], 1.19; 95% confidence interval [CI], 1.15-1.24), atopic dermatitis (RR, 1.10; 95% CI, 1.04-1.16), allergic rhinitis (RR, 1.17; 95% CI, 1.14-1.21), allergic conjunctivitis (RR, 1.13; 95% CI, 1.09-1.17), and any of these atopic diseases (RR, 1.13; 95% CI, 1.10-1.15).

CONCLUSION

The unaffected siblings of ADHD probands were more likely to develop atopic diseases compared with the controls, suggesting shared risk factors for both diseases.

Recent developments and highlights in mechanisms of allergic diseases: Microbiome

All body surfaces are exposed to a wide variety of microbes, which significantly influence immune reactivity within the host. This review provides an update on some of the critical novel findings that have been published on the influence of the microbiome on atopic dermatitis, food allergy and asthma. Microbial dysbiosis has consistently been observed in the skin, gut and lungs of patients with atopic dermatitis, food allergy and asthma, respectively, and the role of specific microbes in allergic disorders is being intensively investigated. However, many of these discoveries have yet to be translated into routine clinical practice.

Association of STAT6 gene variants with food allergy diagnosed by double-blind placebo-controlled food challenges

This study describes the role of two STAT6 gene variants in food allergy using data of patients and their parents who underwent double‐blind placebo‐controlled food challenges (DBPCFCs). After quality control, 369 trios were analysed including 262 children (71.0%) with food allergy. Associations were tested by the Family based association test. The A alleles of both SNPs were associated with food allergy (P = .036 and P = .013 for rs324015 and rs1059513, respectively). Furthermore, these A alleles were associated with peanut allergy, higher sIgE levels to both peanut and cow's milk, more severe symptoms and higher eliciting doses during peanut and cow's milk DBPCFCs (all P < .05). In silico analysis indicates that the identified risk variants increase STAT6 expression which stimulates the differentiation of CD4 +  T cells to the Th2 subset. In conclusion, STAT6 variants may be involved in the pathophysiology of food allergy and their role seems to be independent of the allergenic food.

The Initiation of Th2 Immunity Towards Food Allergens

In contrast with Th1 immune responses against pathogenic viruses and bacteria, the incipient events that generate Th2 responses remain less understood. One difficulty in the identification of universal operating principles stems from the diversity of entities against which cellular and molecular Th2 responses are produced. Such responses are launched against harmful macroscopic parasites and noxious substances, such as venoms, but also against largely innocuous allergens. This suggests that the established understanding about sense and recognition applied to Th1 responses may not be translatable to Th2 responses. This review will discuss processes and signals known to occur in Th2 responses, particularly in the context of food allergy. We propose that perturbations of homeostasis at barrier sites induced by external or internal subverters, which can activate or lower the threshold activation of the immune system, are the major requirement for allergic sensitization. Innate signals produced in the tissue under these conditions equip dendritic cells with a program that forms an adaptive Th2 response.

Regulatory Immune Mechanisms in Tolerance to Food Allergy

Oral tolerance can develop after frequent exposure to food allergens. Upon ingestion, food is digested into small protein fragments in the gastrointestinal tract. Small food particles are later absorbed into the human body. Interestingly, some of these ingested food proteins can cause allergic immune responses, which can lead to food allergy. So far it has not been completely elucidated how these proteins become immunogenic and cause food allergies. In contrast, oral tolerance helps to prevent the pathologic reactions against different types of food antigens from animal or plant origin. Tolerance to food is mainly acquired by dendritic cells, epithelial cells in the gut, and the gut microbiome. A subset of CD103⁺ DCs is capable of inducing T regulatory cells (Treg cells) that express anti-inflammatory cytokines. Anergic T cells also contribute to oral tolerance, by reducing the number of effector cells. Similar to Treg cells, B regulatory cells (Breg cells) suppress effector T cells and contribute to the immune tolerance to food allergens. Furthermore, the human microbiome is an essential mediator in the induction of oral tolerance or food allergy. In this review, we outline the current understanding of regulatory immune mechanisms in oral tolerance. The biological changes reflecting early consequences of immune stimulation with food allergens should provide useful information for the development of novel therapeutic treatments.