RELMβ sets the threshold for microbiome-dependent oral tolerance.

Tolerance to dietary antigens is critical for avoiding deleterious type 2 immune responses resulting in food allergy (FA) and anaphylaxis. However, the mechanisms resulting in both the maintenance and failure of tolerance to food antigens are poorly understood. Here we demonstrate that the goblet-cell-derived resistin-like molecule β (RELMβ) is a critical regulator of oral tolerance.

Pathogenic mechanisms in the evolution of food allergy.

The early development of the neonatal immune system is profoundly influenced by exposure to dietary and microbial antigens, which shapes mucosal tolerance. Successful oral tolerance induction is crucially dependent on microbially imprinted immune cells, most notably the RORγt regulatory T (Treg) and antigen presenting cells and is essential for preventing food allergy (FA). The development of FA can be envisioned to result from disruptions at key checkpoints (CKPTs) that govern oral tolerance induction.

Regulatory T cells in allergic inflammation.

Regulatory T (Treg) cells maintain immune tolerance to allergens at the environmental interfaces in the airways, skin and gut, marshalling in the process distinct immune regulatory circuits operative in the respective tissues. Treg cells are coordinately mobilized with allergic effector mechanisms in the context of a tissue-protective allergic inflammatory response against parasites, toxins and potentially harmful allergens, serving to both limit the inflammation and promote local tissue repair. Allergic diseases are associated with subverted Treg cell responses whereby a chronic allergic inflammatory environment can skew Treg cells toward pathogenic phenotypes that both perpetuate and aggravate disease.

Evaluation of the Suppressive Capacity of Regulatory T Cells in Food Allergy Research.

Regulatory T cells (Treg) exert a crucial role in the suppression of exacerbated T helper (Th) cell responses, including those of type 2 Th (Th2) cells, and in the maintenance of tolerance to environmental antigens and food allergens. The functional capacity of Tregs to suppress Th2 responses has been studied through activation and immunosuppression assays using cells from mice and humans. The immunosuppression assay is an essential in vitro tool that allows the evaluation of the Treg capacity to limit the proliferation and expansion of conventional T cells.

Coculture of Human Dendritic and T Cells for the Study of Specific T Cell-Mediated Responses Against Food Allergens.

Dendritic cells (DCs) connect innate and adaptive immunity by sampling, capturing, processing, and presenting the allergen to distinct subsets of CD4 T cells. In food allergy, this process leads to the generation of allergen-specific Th2 responses and the production of type 2 cytokines that ultimately induce the synthesis of IgE by allergen-specific B cells. In this chapter, we have described different protocols for the isolation of circulating DCs as well as the generation of DC-like cells derived from autologous peripheral monocytes and the human monocytic THP-1 cell line.

Bos d 13, A Novel Heat-Stable Beef Allergen.

Scope: Red meat, a staple food of Western diets, can also induce IgE-mediated allergic reactions. Yet, apart from the heat-labile protein serum albumin and the carbohydrate α-Gal, the molecules causing allergic reactions to red meat remain unknown.

Methods And Results: IgE reactivity profiles of beef-sensitized individuals are analyzed by IgE-immunoblotting with protein extracts from raw and cooked beef.

Critical features of an in vitro intestinal absorption model to study the first key aspects underlying food allergen sensitization.

New types of protein sources will enter our diet in a near future, reinforcing the need for a straightforward in vitro (cell-based) screening model to test and predict the safety of these novel proteins, in particular their potential risk for de novo allergic sensitization. The Adverse Outcome Pathway (AOP) for allergen sensitization describes the current knowledge of key events underlying the complex cellular interactions that proceed allergic food sensitization. Currently, there is no consensus on the in vitro model to study the intestinal translocation of proteins as well as the epithelial activation, which comprise the first molecular initiation events (ME1-3) and the first key event of the AOP, respectively.

IgE-Binding and Immunostimulating Properties of Enzymatic Crosslinked Milk Proteins as Influenced by Food Matrix and Digestibility.

Dairy foods are essential in the diet, although in some susceptible individuals they may cause allergy to cow's milk proteins. Therefore, alternative methods are sought to reduce their allergenicity. Transglutaminase (TG) is widely used in dairy products mainly to improve texture.

Control of Listeria monocytogenes growth and virulence in a traditional soft cheese model system based on lactic acid bacteria and a whey protein hydrolysate with antimicrobial activity.

"Torta del Casar" is a Spanish soft-ripened cheese made with sheep's raw milk and subjected to a short ripening process, which favors the growth of pathogenic microorganisms including Listeria monocytogenes. The development of strategies to control pathogens and minimize health risks associated with the presence of L. monocytogenes in these products is of great interest.

Triacylglycerides and Phospholipids from Egg Yolk Differently Influence the Immunostimulating Properties of Egg White Proteins.

As part of a whole egg, egg white proteins are embedded in a lipid matrix that could modify their presentation to the immune system and their allergenic properties. The present study examines the impact of the main egg lipid components, triacylglycerides and phospholipids, in the early events of sensitization to egg. To this end, BALB/c mice were exposed intragastrically to egg lipids and egg lipid fractions, alone and in mixtures with egg white proteins, and Th2-promoting and proinflammatory effects were investigated.

Storage Proteins Are Driving Pediatric Hazelnut Allergy in a Lipid Transfer Protein-Rich Area.

Oral food challenge (OFC) remains the gold standard for the diagnosis of food allergies. However, this test is not without risks, given that severe allergic reactions can be triggered while it is conducted. The purpose of this study is to identify potential demographic variables, clinical characteristics of the patients and biomarkers that may be associated with severe reactions during the hazelnut oral challenge test.

Retinoic Acid Induces Functionally Suppressive Foxp3RORγt T Cells .

Introduction: CD4 T cells with regulatory function co-expressing Foxp3 and RORγt are linked to the development of oral tolerance towards innocuous food antigens in mice. This study aimed to discern the role played by IL-6 and retinoic acid (RA) in the generation of Foxp3RORγt T cells and to investigate whether such cells have suppressive properties.

Methods: CD4CD25 T cells isolated from the spleen of BALB/c mice, were stimulated in the presence of IL-2 alone or together with TFG-β and different concentrations of IL-6 and/or RA.

Oral Exposure to House Dust Mite Activates Intestinal Innate Immunity.

Scope: House dust mite (HDM) induces Th2 responses in lungs and skin, but its effects in the intestine are poorly known. We aimed to study the involvement of HDM in the initial events that would promote sensitization through the oral route and eventually lead to allergy development.

Methods And Results: BALB/c mice were exposed intragastrically to proteolytically active and inactive HDM, as such, or in combination with egg white (EW), and inflammatory and type 2 responses were evaluated.

IgE-Reactivity Pattern of Tomato Seed and Peel Nonspecific Lipid-Transfer Proteins after Gastrointestinal Digestion.

The influence of gastrointestinal digestion on the immunological properties of three different nonspecific lipid-transfer proteins (nsLTPs) described in tomato fruit has been assessed using an system mimicking the stomach and intestine digestion conditions. Tomato peel/pulp nsLTP, Sola l 3, was degraded after digestion, although the immunoglobulin E (IgE) recognition of intact protein and a 10 kDa band were still observed after 30 min of duodenal digestion in the presence of phosphatidylcholine. The tomato seed nsLTP, Sola l 7, showed a higher stability than the other seed allergen, Sola l 6, during digestion.

Ovalbumin-Derived Peptides Activate Retinoic Acid Signalling Pathways and Induce Regulatory Responses Through Toll-Like Receptor Interactions.

This study investigates the potential of a hydrolysate of ovalbumin with pepsin (OP) to preclude Th2-type immunity by the enhancement of tolerogenic dendritic cells (DCs) and regulatory T (Treg) cells. Through Toll-like receptor (TLR) stimulation, OP enhances the retinoic acid pathway on DCs by means of the induction of aldehyde dehydrogenase enzymes and transforming growth factor beta (TGF-β), and it confers upon DC the ability to upregulate interleukin 10 (IL-10) as well as other tolerance-promoting mediators downstream of TRL signalling, such as IL-27, IL-33, Notch ligands, OX40L, and the transcription factors IRF4 and IRF8. OP-conditioned DCs induce the expansion of Foxp3+ and Tr1 cells in co-culture with CD4+ T cells.

Egg yolk augments type 2 immunity by activating innate cells.

Purpose: Egg yolk (EY) may play a role during the sensitizing phase of egg allergy by exerting intestinal type 2-biasing effects. We aimed to identify the mechanism and role of EY in the induction of allergy to egg white (EW).

Methods: BALB/c mice were exposed intragastrically to EW, EY, or the mixture of EW:EY.

Oral Immunotherapy with Egg Peptides Induces Innate and Adaptive Tolerogenic Responses.

Scope: The mechanism through which peptide-based immunotherapy provides effective desensitization toward food allergy is investigated.

Methods And Results: Ex vivo experiments are conducted with intestinal epithelial cells (IECs), dendritic cells (DCs), and T cells from mice sensitized to egg white (EW) and either left untreated or tolerized by the oral administration of a hydrolysate of ovalbumin with pepsin (OP). IECs from EW-sensitized mice upregulate Il33 and Tslp to a higher extent than those from tolerized mice and induce bone marrow (BM)-DCs to express Tnfsf4 and produce pro-inflammatory cytokines.

Egg Yolk Provides Th2 Adjuvant Stimuli and Promotes Sensitization to Egg White Allergens in BALB/c Mice.

Scope: Egg is the second most frequent source of allergic reactions in children. Egg yolk (EY) amounts to one-third in weight of a fresh whole egg, but its contribution to egg allergy has not been investigated in depth. This study assesses whether EY influences the capacity of egg white (EW) to sensitize and trigger allergic responses.

Sensitizing and Eliciting Capacity of Egg White Proteins in BALB/c Mice As Affected by Processing.

This study assesses to what extent technological processes that lead to different degrees of denaturation of egg white proteins affect their allergenicity. We focused on heat (80 °C, 10 min) and high-pressure (400 MPa and 37 °C, 10 min) treatments and used a BALB/c mouse model of food allergy. Oral sensitization to egg white using cholera toxin as adjuvant induced the production of IgE and IgG1 isotypes and led to severe clinical signs following challenge with the allergen.