Initiation Of Allergic Responses Research Articles

Bcl2L12 plays a critical role in the development of intestinal allergy

The skewed T helper (Th) 2 response plays a central role in the pathogenesis of allergic diseases, while its initiating factors remain elusive. Recent studies indicate that Bcl2 like protein-12 (Bcl2L12) is associated with the Th2-biased inflammation. This study is designed to test a hypothesis that Bcl2L12 plays a critical role in the initiation of allergic response. In this study, peripheral CD4+ T cells were isolated from food allergy (FA) patients and healthy subjects; A mouse FA model was developed to test the role of Bcl2L12 in induction of allergic response in the intestine. The results showed that expression of Bcl2L12 by CD4+ T cells was higher in FA patients and FA mice and positively correlated with expression of Th2 cytokines. CD4+ T cells from FA patients showed a Bcl2L12-dependent tendency to differentiate into Th2 cells. Bcl2L12 played a crucial role in induction of allergic response in the intestine. Physical contact between Bcl2L12 and GATA3 facilitated GATA3 to bind Il4 promoter to promote expression of IL-4. Adoptive transfer with Bcl2L12-deficient CD4+ T cells to Rag2¯/¯ mice did not reconstitute the efficient CD4+ T cell response as the mice could not be induced FA, while Rag2¯/¯ mice received WT CD4+ T cell transfer were induced FA. In conclusion, Bcl2L12 plays a crucial role in the induction of Th2 polarization and allergic response in the intestine. The Bcl2L12 in CD4+ T cells may be a potential target for the treatment of FA.

Sex-bias in allergic asthma: androgens and group 2 innate lymphoid cells

Allergic asthma is a chronic pulmonary inflammatory disease initiated by exposure to normally harmless allergens and marked by bronchial hyperreactivity. It affects more than 300 million people worldwide. Asthma often starts in childhood. Epidemiological studies show that there are sexual disparities in the prevalence and severity of asthma. Before the age of 10, the disease is more common in boys. This tendency reverses at puberty suggesting a regulating role of the sex hormones. In this synthesis, we summarize current knowledge on the role of sex hormones in allergic inflammation, with a particular focus on the impact of androgens on the development and function of recently introduced group 2 innate lymphoid cell subsets (ILC2) as critical actors in the initiation of allergic responses.♢.

Sex Differences in Asthma: A Key Role of Androgen-Signaling in Group 2 Innate Lymphoid Cells.

Infectious diseases, autoimmune diseases, and also allergy differentially affect women and men. In general, women develop strongest immune responses and thus the proportion of infected individuals and the severity of many viral, bacterial, or parasitic infections are increased in men. However, heightened immunity in women makes them more susceptible than men to autoimmunity and allergy. While sex differences in immunity are well documented, little is known about the cellular and molecular mechanisms underlying these immunological differences, particularly in allergic asthma. Asthma is a chronic inflammation of the airways mediated by exacerbated type 2 immune responses. Sex differences have been reported in the incidence, prevalence, and severity of asthma. While during childhood, males are more susceptible to asthma than females, there is a switch at the onset of puberty as for many other allergic diseases. This decrease of asthma incidence around puberty in males suggests that hormonal mediators could play a protective role in the susceptibility to allergic responses in male. Group 2 innate lymphoid cells (ILC2s) have recently emerged as critical players in the initiation of allergic responses, but also in the resolution of parasitic infection, through their capacity to rapidly and potently produce type 2 cytokines. This review will cover the current understanding of the impact of sex-linked factors in allergic inflammation, with a particular focus on the role of sex hormones on the development and function of tissue-resident ILC2s.

Transepithelial initiation of allergic response

The paper is focused on structure and functions of airway epithelial barrier and allergen-mediated innate immune response of the epithelium leading to facilitation of allergy development.

IL-33 Precedes IL-5 in Regulating Eosinophil Commitment and Is Required for Eosinophil Homeostasis.

Eosinophils are important in the pathogenesis of many diseases, including asthma, eosinophilic esophagitis, and eczema. Whereas IL-5 is crucial for supporting mature eosinophils (EoMs), the signals that support earlier eosinophil lineage events are less defined. The IL-33R, ST2, is expressed on several inflammatory cells, including eosinophils, and is best characterized for its role during the initiation of allergic responses in peripheral tissues. Recently, ST2 expression was described on hematopoietic progenitor subsets, where its function remains controversial. Our findings demonstrate that IL-33 is required for basal eosinophil homeostasis, because both IL-33- and ST2-deficient mice exhibited diminished peripheral blood eosinophil numbers at baseline. Exogenous IL-33 administration increased EoMs in both the bone marrow and the periphery in wild-type and IL-33-deficient, but not ST2-deficient, mice. Systemic IL-5 was also increased under this treatment, and blocking IL-5 with a neutralizing Ab ablated the IL-33-induced EoM expansion. The homeostatic hypereosinophilia seen in IL-5-transgenic mice was significantly lower with ST2 deficiency despite similar elevations in systemic IL-5. Finally, in vitro treatment of bone marrow cells with IL-33, but not IL-5, led to specific early expansion of IL-5Rα-expressing precursor cells. In summary, our findings establish a basal defect in eosinophilopoiesis in IL-33- and ST2-deficient mice and a mechanism whereby IL-33 supports EoMs by driving both systemic IL-5 production and the expansion of IL-5Rα-expressing precursor cells.

Eosinophil lineage commitment and IL-5-dependent expansion is regulated by IL-33 in mice

Abstract Eosinophils are important in the pathogenesis of many diseases, including asthma, eosinophilic esophagitis and eczema. While IL-5 is necessary for the maturation of eosinophil progenitors (EoP) into mature eosinophils (EoM), the signals that promote commitment to the eosinophil lineage are unknown. The IL-33 receptor, ST2, is expressed on several inflammatory cells, including eosinophils, and is best characterized for its role during the initiation of allergic responses in the peripheral tissues. Recently, ST2 expression was described on hematopoietic stem cells, where its function remains unclear. Here, we sought to determine whether IL-33 and ST2 contribute to hematopoietic lineage decisions. We found that both IL-33- and ST2-deficient mice exhibited diminished peripheral blood eosinophils at baseline. Correspondingly, IL-33 administration increased EoM as well as IL-5 in the blood and bone marrow in WT and IL-33-deficient but not ST2-deficient mice. Blocking IL-5 with a neutralizing antibody prevented IL-33-expanded EoP from maturing into EoM, while transgenic overexpression of IL-5 in ST2-deficient mice resulted in significantly lower hypereosinophilia than transgenic IL-5 mice. Finally, we observed that IL-33, but not IL-5, specifically expanded EoP and upregulated IL-5Rα on EoP as well as increased IL-5 after bone marrow was cultured for three days. Our findings identify a basal defect in eosinophilopoiesis in IL-33- and ST2-deficient mice. Furthermore, we establish unappreciated roles for IL-33 and ST2 in eosinophil development via progenitor regulation and define a mechanism whereby IL-33 licenses commitment into the eosinophil lineage by driving both responsiveness to IL-5 and IL-5 production.

The ΙgΕ-epitome viewed through the eyes of human monoclonal ΙgΕ

Background Despite the key role of IgE as the allergen recognizer at the initiation of allergic responses our knowledge on the molecular interactions between human IgE and allergen is limited. To date, most studies aiming at identification of IgE-reactive epitopes have had to rely on polyclonal IgE-preparations, non-human antibodies or antibodies of isotypes other than IgE. However, due to their intrinsic ability to recognize highly relevant, in the context of allergy, epitopes on allergens, allergen-specific human monoclonal IgE, represented by recombinant human antibody fragments, offer an opportunity to decipher the IgE-epitome of major allergens with precision and at high resolution. Such information may guide us in development of novel therapeutic candidates and better diagnostic tools. Methods We have isolated a large pool of antibody variable domain fragments, specific for several major allergens, from the IgE repertoires of allergic donors. Three sets of such binders, targeting the major birch pollen allergen Bet v 1 (n = 4) and the major timothy grass pollen allergens Phl p 1 (n = 5) and Phl p 5 (n = 10), and their interactions with respective allergen have been studied by immunochemical methodologies. Results We have, using our own technology and through collaborations, been able to define multiple non-overlapping IgE-reactive epitopes on all three investigated allergens. Two novel epitopes on Bet v 1 were identified, which allowed for identification of single amino acid residues with crucial importance for the interaction between human IgE and allergens in the PR-10 protein family. Further, it was shown that the relatively small allergen Phl p 5 carries a complex composition of IgE-reactive epitopes, providing an explanation to its high allergenicity. The less complex epitope composition on Phl p 1, on the other hand, with an IgE-binding hot-spot located on the surface of its immunodominant C-terminal domain, allowed us to, in a rational manner, design a hypoallergenic group 1 gras sp ollen allergen fragment, with the potential to be used as a safer alternative to the today used extracts in specific immunotherapy. Conclusion

Cutting Edge: Allergen-Specific CD4 T Cells Respond Indirectly to Thymic Stromal Lymphopoietin To Promote Allergic Responses in the Skin

Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine that has been implicated in the initiation of allergic responses. CD4 T cells and dendritic cells are able to respond to TSLP in vitro; however, there has not been a careful dissection of the spatiotemporal response to TSLP by CD4 T cells in vivo during an allergic response. Previous work has suggested a requirement for TSLP in amplifying Th2 responses during allergen challenge by direct action on CD4 T cells; however, these studies did not determine whether there is an effect of TSLP on CD4 T cells during allergen sensitization. In this study we demonstrate an indirect role for TSLP on CD4 T cells during sensitization and challenge phases of an allergic response. This indirect effect of TSLP on CD4 T cells is due in part to the presence of TSLP exclusively in the allergen-sensitized and -challenged skin, rather than the draining lymph nodes.

Environmental and occupational respiratory diseases – 1056. Enhancement of sensitivity for human airway epithelial cells to house dust mites by respiratory syncytial virus infection

Background Airway is one of the main routes for allergen exposure and entering airborne allergens through the airway can initiate allergic responses, resulting in development of allergic asthma. There are various environmental factors that also influence to the airway-mediated immune responses. Among the factors, respiratory syncytial virus (RSV) enables the condition of the airway to change because RSV infection is common in early life and induce the bronchiolitis. In addition, several studies have been reported that non-immune cells such as airway epithelial cells play a pivotal role in the initiation of allergic responses. The aim of our study is to determine the association between the sensitization of common airborne allergens and RSV infection in airway epithelial cells.

Opposing roles of IL‐17A and IL‐25 in the regulation of TSLP production in human nasal epithelial cells

The importance of IL-17A, IL-17F, and IL-25 in allergic rhinitis (AR), as well as their possible role in regulation on thymic stromal lymphopoietin (TSLP) production in nasal epithelial cells, is not well understood. To determine the possible regulation of IL-17A, IL-17F, and IL-25 on TSLP production in the initiation of allergic responses. The levels of IL-17A, IL-17F, IL-25, and TSLP in nasal lavages of patients with AR were measured using an enzyme-linked immunosorbent assay (ELISA) and compared with that in normal controls. Then, primary human nasal epithelial cells (HNECs) were stimulated with dsRNA (0-75 microg/ml), as well as IL-17A (100 ng/ml), IL-17F (100 ng/ml), and IL-25(100 ng/ml). The mRNA expression of IL-17A, IL-17F, IL-25, TSLP, as well as the chemokines CCL20, IL-8, and eotaxin was analyzed using quantitative real-time PCR, and their protein levels in the supernatants of cultured HNECs were determined by ELISA. Both TSLP and IL-17 cytokines are significantly elevated in patients with AR. dsRNA was found to increase the production of IL-17F, IL-25, TSLP, CCL20, and IL-8 in HNECs. Furthermore, IL-25 significantly enhanced dsRNA-induced TSLP production in primary HNECs and was dominant to the inhibitory effect of IL-17A on TSLP regulation. Our study provides the first evidence that both IL-17F and IL-25 can be induced by dsRNA in HNECs. Despite of the opposing effects of IL-17A and IL-25 on TSLP regulation in HNECs, IL-25 was dominant to IL-17A, providing a plausible explanation for the simultaneous upregulation of IL-17 cytokines and TSLP in patients with AR.

The FcεRIβ Subunit Functions as an Amplifier of FcεRIγ-Mediated Cell Activation Signals

The high affinity IgE receptor (FcεRI) plays a central role in the initiation of allergic responses. FcεRI is multimeric and is expressed as either αγ 2 trimers or αβγ 2 tetramers. Recently, polymorphisms of the β chain gene have been associated with the development of various allergic phenotypes. Until now, the role of β in FcεRI-dependent signaling was largely unknown. For that reason, we compared the signaling characteristics of various wild-type and mutant αγ 2 and αβγ 2 FcεRI complexes. These studies demonstrate that the γ dimer functions as an autonomous activation module, while β functions as an amplifier that provides a gain of 5- to 7-fold, as measured by Syk activation and calcium mobilization.