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Introduction: Food allergic reactions can be severe and potentially life‐threatening and the underlying immunological processes that contribute to the severity of reactions are poorly understood. The aim of this study is to integrate bulk RNA‐sequencing of human and mouse peripheral blood mononuclear cells during food allergic reactions and in vivo mouse models of food allergy to identify dysregulated immunological processes associated with severe food allergic reactions. Methods: Bulk transcriptomics of whole blood from human and mouse following food allergic reactions combined with integrative differential expressed gene bivariate and module eigengene network analyses to identify the whole blood transcriptome associated with food allergy severity. In vivo validation immune cell and gene expression in mice following IgE‐mediated reaction. Results: Bulk transcriptomics of whole blood from mice with different severity of food allergy identified gene ontology (GO) biological processes associated with innate and inflammatory immune responses, dysregulation of MAPK and NFkB signalling and identified 429 genes that correlated with reaction severity. Utilizing two independent human cohorts, we identified 335 genes that correlated with severity of peanut‐induced food allergic reactions. Mapping mouse food allergy severity transcriptome onto the human transcriptome revealed 11 genes significantly dysregulated and correlated with severity. Analyses of whole blood from mice undergoing an IgE‐mediated reaction revealed a rapid change in blood leukocytes particularly inflammatory monocytes (Ly6Chi Ly6G−) and neutrophils that was associated with changes in CLEC4E, CD218A and GPR27 surface expression. Conclusions: Collectively, IgE‐mediated food allergy severity is associated with a rapid innate inflammatory response associated with acute cellular stress processes and dysregulation of peripheral blood inflammatory myeloid cell frequencies. [ABSTRACT FROM AUTHOR]

Food allergy is an emerging epidemic, and the underlying mechanisms are not well defined partly due to the lack of robust adjuvant free experimental models of dietary antigen sensitization. As housing mice at thermoneutrality (Tn) - the temperature of metabolic homeostasis (26–30°C) – has been shown to improve modeling various human diseases involved in inflammation, we tested the impact of Tn housing on an experimental model of food sensitization. Here we demonstrate that WT BALB/c mice housed under standard temperature (18–20°C, Ts) conditions translocated the luminal antigens in the small intestine (SI) across the epithelium via goblet cell antigen passages (GAPs). In contrast, food allergy sensitive Il4ra F709 mice housed under standard temperature conditions translocated the luminal antigens in the SI across the epithelium via secretory antigen passages (SAPs). Activation of SI antigen passages and oral challenge of Il4ra F709 mice with egg allergens at standard temperature predisposed Il4ra F709 mice to develop an anaphylactic reaction. Housing Il4ra F709 mice at Tn altered systemic type 2 cytokine, IL-4, and the landscape of SI antigen passage patterning (villus and crypt involvement). Activation of SI antigen passages and oral challenge of Il4ra F709 mice with egg antigen under Tn conditions led to the robust induction of egg-specific IgE and development of food-induced mast cell activation and hypovolemic shock. Similarly, Tn housing of WT BALB/c mice altered the cellular patterning of SI antigen passage (GAPs to SAPs). Activation of SI antigen passages and the oral challenge of WT BALB/c mice with egg antigen led to systemic reactivity to egg and mast cell activation. Together these data demonstrate that Tn housing alters antigen passage cellular patterning and landscape, and concurrent oral exposure of egg antigens and SAP activation is sufficient to induce oral antigen sensitization. [ABSTRACT FROM AUTHOR]

Background: Previous studies have revealed an important role for the transcription factor GATA-1 in mast cell maturation and degranulation. However, there have been conflicting reports with respect to the requirement of GATA-1 function in mast cell dependent inflammatory processes. Herein, we examine the requirement of GATA-1 signaling in mast cell effector function and IgE-mast cell-dependent anaphylaxis. Objective: To study the requirement of GATA-1 dependent signaling in the development and severity of IgE-mast cell-dependent anaphylaxis in mice. Methods: Wild type (Balb/c) and mutant ΔdblGata (Balb/c) mice were employed to study the role of GATA-1 signaling in in vitro IgE-mediated activation of bone marrow derived mast cells (BMMCs). Murine models of passive IgE-mediated and oral antigen-induced IgE-mediated anaphylaxis were employed in mice. Frequency of steady state mast cells in various tissues (duodenum, ear, and tongue), peritoneal cavity, and clinical symptoms (diarrhea, shock, and mast cell activation) and intestinal Type 2 immune cell analysis including CD4+ Th2 cells, type 2 innate lymphoid cells (ILC2), and IL-9 secreting mucosal mast cells (MMC9) were assessed Results: In vitro analysis revealed that ΔdblGata BMMCs exhibit a reduced maturation rate, decreased expression of FcεRIα, and degranulation capacity when compared to their wildtype (WT) counterparts. These in vitro differences did not impact tissue resident mast cell numbers, total IgE, and susceptibility to or severity of IgE-mediated passive anaphylaxis. Surprisingly, ΔdblGata mice were more susceptible to IgE-mast cell-mediated oral antigen induced anaphylaxis. The increased allergic response was associated with increased Type 2 immunity (antigen-specific IgE, and CD4+ TH2 cells), MMC9 cells and small intestine (SI) mast cell load. Conclusion: Diminished GATA-1 activity results in reduced in vitro mast cell FcεRIα expression, proliferation, and degranulation activity. However, in vivo, diminished GATA-1 activity results in normal homeostatic tissue mast cell levels and increased antigen-induced CD4+ Th2 and iMMC9 cell levels and heightened IgE-mast cell mediated reactions. [ABSTRACT FROM AUTHOR]

Susceptibility to inflammatory bowel diseases (IBDs), Crohn's disease (CD), and ulcerative colitis (UC) is linked with loss of intestinal epithelial barrier integrity and mitochondria dysfunction. Steroidogenic acute regulatory (StAR) protein-related lipid transfer (START) domain-containing protein 7 (STARD7) is a phosphatidylcholine-specific (PC-specific) lipid transfer protein that transports PC from the ER to the mitochondria, facilitating mitochondria membrane stabilization and respiration function. The aim of this study was to define the contribution of STARD7 in the regulation of the intestinal epithelial mitochondrial function and susceptibility to colitis. In silico analyses identified significantly reduced expression of STARD7 in patients with UC, which was associated with downregulation of metabolic function and a more severe disease phenotype. STARD7 was expressed in intestinal epithelial cells, and STARD7 knockdown resulted in deformed mitochondria and diminished aerobic respiration. Loss of mitochondria function was associated with reduced expression of tight junction proteins and loss of intestinal epithelial barrier integrity that could be recovered by AMPK activation. Stard7+/- mice were more susceptible to the development of DSS-induced and Il10-/- spontaneous models of colitis. STARD7 is critical for intestinal epithelial mitochondrial function and barrier integrity, and loss of STARD7 function increases susceptibility to IBD.

Background & Aims: CD4 + T cells are regulated by activating and inhibitory cues, and dysregulation of these proper regulatory inputs predisposes these cells to aberrant inflammation and exacerbation of disease. We investigated the role of the inhibitory receptor paired immunoglobulin-like receptor B (PIR-B) in the regulation of the CD4 + T-cell inflammatory response and exacerbation of the colitic phenotype., Methods: We used Il10 -/- spontaneous and CD4 + CD45RB hi T-cell transfer models of colitis with PIR-B-deficient (Pirb -/- ) mice. Flow cytometry, Western blot, and RNA sequencing analysis was performed on wild-type and Pirb -/- CD4 + T cells. In silico analyses were performed on RNA sequencing data set of ileal biopsy samples from pediatric CD and non-inflammatory bowel disease patients and sorted human memory CD4 + T cells., Results: We identified PIR-B expression on memory CD4 + interleukin (IL)17a + cells. We show that PIR-B regulates CD4 + T-helper 17 cell (Th17)-dependent chronic intestinal inflammatory responses and the development of colitis. Mechanistically, we show that the PIR-B- Src-homology region 2 domain-containing phosphatase-1/2 axis tempers mammalian target of rapamycin complex 1 signaling and mammalian target of rapamycin complex 1-dependent caspase-3/7 apoptosis, resulting in CD4 + IL17a + cell survival. In silico analyses showed enrichment of transcriptional signatures for Th17 cells (RORC, RORA, and IL17A) and tissue resident memory (HOBIT, IL7R, and BLIMP1) networks in PIR-B + murine CD4 + T cells and human CD4 + T cells that express the human homologue leukocyte immunoglobulin-like receptor subfamily B member 3 (LILRB3). High levels of LILRB3 expression were associated strongly with mucosal injury and a proinflammatory Th17 signature, and this signature was restricted to a treatment-naïve, severe pediatric CD population., Conclusions: Our findings show an intrinsic role for PIR-B/LILRB3 in the regulation of CD4 + IL17a + T-cell pathogenic memory responses., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)