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Inflammatory bowel disease (IBD) pathogenesis is associated with dysregulated [CD4.sup.+] Th cell responses, with intestinal homeostasis depending on the balance between IL-17-producing Th17 and [Foxp3.sup.+] Tregs. Differentiation of naive T cells into Th17 and Treg subsets is associated with specific gene expression profiles; however, the contribution of epigenetic mechanisms to controlling Th17 and Treg differentiation remains unclear. Using a murine T cell transfer model of colitis, we found that T cell-intrinsic expression of the histone lysine methyltransferase G9A was required for development of pathogenic T cells and intestinal inflammation. G9A-mediated dimethylation of histone H3 lysine 9 (H3K9me2) restricted Th17 and Treg differentiation in vitro and in vivo. H3K9me2 was found at high levels in naive Th cells and was lost following Th cell activation. Loss of G9A in naive T cells was associated with increased chromatin accessibility and heightened sensitivity to TGF-P1. Pharmacological inhibition ofG9A methyltransferase activity in WT T cells promoted Th17 and Treg differentiation. Our data indicate that G9A-dependent H3K9me2 is a homeostatic epigenetic checkpoint that regulates Th17 and Treg responses by limiting chromatin accessibility and TGF-β1 responsiveness, suggesting G9A as a therapeutic target for treating intestinal inflammation., Introduction The inflammatory bowel diseases (IBDs) are a group of chronic intestinal inflammatory diseases that include ulcerative colitis (UC) and Crohn disease (CD). IBD is thought to occur as a [...]

Abstract Background Allergy to peanuts results in severe anaphylactic responses in affected individuals, and has dramatic effects on society and public policy. Despite the health impacts of peanut-induced anaphylaxis (PIA), relatively little is known about immune mechanisms underlying the disease. Using a mouse model of PIA, we evaluated mice with deletions in four distinct immune molecules (IL7Rα, L-selectin, CD34, CD103), for perturbed responses. Methods PIA was induced by intragastric sensitization with peanut antigen and cholera toxin adjuvant, followed by intraperitoneal challenge with crude peanut extract (CPE). Disease outcome was assessed by monitoring body temperature, clinical symptoms, and serum histamine levels. Resistant mice were evaluated for total and antigen specific serum IgE, as well as susceptibility to passive systemic anaphylaxis. Results PIA responses were dramatically reduced in IL7Rα−/− and L-selectin−/− mice, despite normal peanut-specific IgE production and susceptibility to passive systemic anaphylaxis. In contrast, CD34−/− and CD103−/− mice exhibited robust PIA responses, indistinguishable from wild type controls. Conclusions Loss of L-selectin or IL7Rα function is sufficient to impair PIA, while CD34 or CD103 ablation has no effect on disease severity. More broadly, our findings suggest that future food allergy interventions should focus on disrupting sensitization to food allergens and limiting antigen-specific late-phase responses. Conversely, therapies targeting immune cell migration following antigen challenge are unlikely to have significant benefits, particularly considering the rapid kinetics of PIA.

In mouse models of infection with the gastrointestinal parasite Trichuris muris, appropriate dendritic-cell (DC) Ag sampling, migration, and presentation to T cells are necessary to mount a protective Th2-polarized adaptive immune response, which is needed to clear infection. SH2-containing inositol 5′-phosphatase 1 (SHIP-1) has been shown to be an important regulator of DC function in vitro through the negative regulation of the phosphoinositide 3-kinase (PI3K) pathway, but its role in vivo is relatively unexplored. In the current work, mice with a specific deletion of SHIP-1 in DCs ( Ship1ΔDC) were infected with the parasite T. muris. Ship1ΔDC mice were susceptible to infection due to ineffective priming of Th2-polarized responses. This is likely due to an increased production of interleukin (IL) 12p40 by SHIP-1-deficient DCs, as in vivo antibody blockade of IL-12p40 was able to facilitate the clearing of infection in Ship1ΔDC mice. Our results describe a critical role for SHIP-1 in regulating the ability of DCs to efficiently prime Th2-type responses. [ABSTRACT FROM AUTHOR]

The article offers insight to Canadian Healthy Infant Longitudinal Development Study focusing on the impact of early infancy microbial and metabolic alterations on the risk of childhood asthma. Topics discussed include link between gut microbial dysbiosis; microbe-derived functional changes in infants; and the role of Faecalibacterium, Lachnospira, Veillonella-mediated amelioration of murine lung inflammation.

Background: Allergic inflammation involves the sensitization of naive CD4+ T cells to allergens, resulting in a TH2-skewed inflammatory response. Although antigen presentation by dendritic cells to T cells in the lymph node is crucial for TH2 cell development, the innate signals that initiate adaptive type 2 inflammation and the role of group 2 innate lymphoid cells (ILC2s) are poorly understood. Objective: We sought to investigate the influence of ILC2s and the route of priming on the development of an adaptive type 2 immune response to lung allergens. Methods: Wild-type and ILC2-deficient mice were exposed intranasally or systemically to the TH2-inducing antigens house dust mite or ovalbumin in a model of allergic airway inflammation or the TH17-inducing bacterial antigen Saccharopolyspora rectivirgula in a model of hypersensitivity pneumonitis. The formation of an adaptive immune response was evaluated based on serum antibody titers and production of T cell–derived cytokines (IL-4, IL-5, IL-13 and IL-17A). Results: We find that lung ILC2s play a critical role in priming the adaptive type 2 immune response to inhaled allergens, including the recruitment of eosinophils, TH2 cytokine production and serum IgE levels. Surprisingly, systemic priming with ovalbumin, with or without adjuvants, circumvents the requirement for ILC2s in inducing TH2-driven lung inflammation. ILC2s were also found to be dispensable for the sensitization to TH1- or TH17-inducing antigens. Conclusion: These data highlight a critical role for ILC2s in the development of adaptive type 2 responses to local, but not systemic, antigen exposure. [Copyright &y& Elsevier]

Fibrosis is the result of dysregulated tissue regeneration and is characterized by excessive accumulation of matrix proteins that become detrimental to tissue function. In Crohn's disease, this manifests itself as recurrent gastrointestinal strictures for which there is no effective therapy beyond surgical intervention. Using a model of infection-induced chronic gut inflammation, we show that Rora -deficient mice are protected from fibrosis; infected intestinal tissues display diminished pathology, attenuated collagen deposition and reduced fibroblast accumulation. Although Rora is best known for its role in ILC2 development, we find that Salmonella -induced fibrosis is independent of eosinophils, STAT6 signaling and Th2 cytokine production arguing that this process is largely ILC2-independent. Instead, we observe reduced levels of ILC3- and T cell-derived IL-17A and IL-22 in infected gut tissues. Furthermore, using Rora sg/sg / Rag1 -/- bone marrow chimeric mice, we show that restoring ILC function is sufficient to re-establish IL-17A and IL-22 production and a profibrotic phenotype. Our results show that RORα-dependent ILC3 functions are pivotal in mediating gut fibrosis and they offer an avenue for therapeutic intervention in Crohn's-like diseases., Competing Interests: Competing interests: The authors declare no competing financial interests.

Although CD103(+) cells recently emerged as key regulatory cells in the gut, the role of CD103 ubiquitous expression in the lung and development of allergic airway disease has never been studied. To answer this important question, we evaluated the response of Cd103(-/-) mice in two separate well-described mouse models of asthma (ovalbumin and house dust mite extract). Pulmonary inflammation was assessed by analysis of bronchoalveolar lavage content, histology, and cytokine response. CD103 expression was analyzed on lung dendritic cells and T cell subsets by flow cytometry. Cd103(-/-) mice exposed to antigens developed exacerbated lung inflammation, characterized by increased eosinophilic infiltration, severe tissue inflammation, and altered cytokine response. In wild-type mice exposed to house dust mite, CD103(+) dendritic cells are increased in the lung and an important subset of CD4(+) T cells, CD8(+) T cells, and T regulatory cells express CD103. Importantly, Cd103(-/-) mice presented a deficiency in the resolution phase of inflammation, which supports an important role for this molecule in the control of inflammation severity. These results suggest an important role for CD103 in the control of airway inflammation in asthma., (Copyright © 2015 the American Physiological Society.)

Purpose: Asthma is a chronic respiratory disorder that leads to inflammation and narrowing of the airways. Its global prevalence has attained epidemic levels and treatment options that reach beyond temporary relief of symptoms are urgently needed. Since the processes leading to clinically symptomatic asthma start early in life, we set out to systematically evaluate a neonatal immunotherapeutic based on Listeria monocytogenes (Lm) for the control of allergic sensitization., Methods: We modified Lm to express the model allergen, ovalbumin (OVA), and tested the ability of neonatal immunization with this strain to control allergic sensitization in a mouse model of OVA-induced asthma. Mice were immunized as newborns with live or heat killed LmOVA or live Lm, followed 6 weeks later by allergic sensitization with OVA. In order to determine whether the TH1-polarizing effect of this vaccine vector inadvertently may exacerbate development of certain TH1-driven allergic diseases, mice immunized as newborns were assessed in a model of adult hypersensitivity pneumonitis (HP)., Results: Both LmOVA and Lm-control vaccines were highly effective in providing long-lasting protection from airway inflammation after only one immunization given perinatally. Serum antibody levels and lung cytokine production suggest that this prophylactic strategy is associated with an allergen specific TH1-dominated response. Specifically, LmOVA vaccinated mice displayed significantly elevated OVA-specific serum IgG2a, but no difference in anti-OVA IgE antibodies and only slightly decreased anti-OVA IgG1 antibodies. Importantly, Lm-based neonatal vaccination did not exacerbate Th1/Th17 driven HP, arguing against broad spectrum immune skewing., Conclusions: Our findings highlight the promise of early life Lm-based immunomodulatory interventions as a prophylactic strategy for allergic asthma.