Project description:IgE antibody is known as a common mediator of allergic responses, generally produced in type 2 immune responses to allergens. It is known that IgE binding to FcεRI without allergen binding promotes survival or proliferation of mast cells, basophils and other cells. Thus, spontaneously produced IgE, namely natural IgE, can increase an individual’s susceptibility to allergic diseases. Mice with a genetic defect in MyD88, a major signaling molecule downstream of Toll-like receptors, have a high level of serum natural IgE, the mechanism for which remains unknown. Here, we demonstrated that the maintenance of high serum IgE levels depends on memory B cells (MBCs). IgE from plasma cells and the sera from most of Myd88–/– mice, but none of Myd88+/– mice, recognized Streptococcus azizii (S. azizii), a commensal bacterium over-represented in the lung of Myd88–/– mice. IgG1+ MBCs from spleen also recognized S. azizii. The serum IgE levels declined by administration of antibiotics and were boosted by challenge with S. azizii in Myd88–/– mice. Moreover, bulk IgH repertoire analysis revealed that CDR3 sequences were highly shared between IgE+ PCs and IgG1+ or IgG2+ MBCs, indicating the contribution of S. azizii-specific IgG1+ MBCs to the natural IgE production.
Project description:Summary: Long-lived IgE plasma cells reside in the bone marrow of allergic mice and atopic humans, confer IgE serological memory and produce allergen-specific IgE that can drive anaphylaxis. Abstract: Immunoglobulin E (IgE) plays an important role in allergic diseases. Nevertheless, the source of IgE serological memory remains controversial. We re-examined the mechanism of serological memory in allergy using a dual-reporter system to track IgE plasma cells (PCs) in mice. Short-term allergen exposure resulted in the generation of IgE plasma cells that resided mainly in secondarylymphoid organs and produced IgE that was unable to degranulate mast cells. In contrast, chronic allergen exposure led to the generation of long-lived IgE plasma cells that were primarily derived from sequential class switching of IgG1, accumulated in the bone marrow (BM) and produced IgE capable of inducing anaphylaxis. Most importantly, IgE plasma cells were found in the BM of human allergic, but not non-allergic donors, and allergen-specific IgE produced by these cells was able to induce mast cell degranulation when transferred to mice. These data demonstrate that longlived IgE BMPCs arise during chronic allergen exposure and establish serological memory in both mice and humans.
Project description:Food allergy is caused by allergen-specific IgE but little is known about the B cell memory of persistent responses. Here we describe in pediatric peanut allergy a population of CD23+IgG1 memory B cells that contains peanut-specific clones and generates IgE plasma cells on activation. Through single cell transcriptomics and B cell receptor (BCR) sequencing, we characterized FCER2/CD23+ IgG1 memory B cells co-expressing IL4R, IL13RA1, IGHE and carrying highly mutated BCRs. Further we found that peanut allergen (Ara h 2)-specific B cells were mostly IgG1 memory cells, carried highly mutated BCRs compared to diphtheria toxin-specific B cells, and expressed FCER2 and germlin IGHE. Our findings suggest that CD23+IgG1+ memory B cells transcribing IGHE are a unique memory population containing precursors for pathogenic IgE in food allergy.
Project description:<h4><strong>BACKGROUND: </strong>IgE-mediated cow's milk allergy (IgE-CMA) is one of the first allergies to arise in early childhood and may result from exposure to various milk allergens, of which β-lactoglobulin (BLG) and casein are the most important. Understanding the underlying mechanisms behind IgE-CMA is imperative for the discovery of novel biomarkers and the design of innovative treatment and prevention strategies.</h4><h4><strong>METHODS: </strong>We report a longitudinal <em>in vivo</em> murine model, in which two mice strains (BALB/c and C57Bl/6) were sensitized to BLG using either cholera toxin or an oil emulsion (n = 6 per group). After sensitization, mice were challenged orally, their clinical signs monitored, antibody (IgE and IgG1) and cytokine levels (IL-4 and IFN-γ) measured, and fecal samples subjected to metabolomics. The results of the murine models were further extrapolated to fecal microbiome-metabolome data from our population of IgE-CMA (n = 22) and healthy (n = 23) children (Trial: NCT04249973), on which polar metabolomics, lipidomics and 16S rRNA metasequencing were performed. In vitro gastrointestinal digestions and multi-omics corroborated the microbial origin of proposed metabolic changes.</h4><h4><strong>RESULTS: </strong>During mice sensitization, we observed multiple microbially derived metabolic alterations, most importantly bile acid, energy and tryptophan metabolites, that preceded allergic inflammation. We confirmed microbial dysbiosis, and its associated effect on metabolic alterations in our patient cohort, through <em>in vitro</em> digestions and multi-omics, which was accompanied by metabolic signatures of low-grade inflammation.</h4><h4><strong>CONCLUSION: </strong>Our results indicate that gut dysbiosis precedes allergic inflammation and nurtures a chronic low-grade inflammation in children on elimination diets, opening important new opportunities for future prevention and treatment strategies.</h4>
Project description:Immunoglobulin (Ig) E-mediated activation of mast cells and basophils underlies allergic diseases such as asthma. Histamine-releasing factor (HRF), also known as translationally controlled tumor protein (TCTP) and fortilin, is a highly conserved protein with both intracellular and extracellular functions. Secreted HRF can stimulate histamine release and IL-4 and IL-13 production from IgE-sensitized basophils and mast cells. HRF is found in nasal, skin blister and bronchoalveolar lavage (BAL) fluids during late-phase allergic reactions (LPRs), which implicates HRF in the LPR and chronic allergic inflammation. Here we identify a subset of IgE and IgG antibodies as HRF-interacting molecules. HRF can exist as a dimer and bind to immunoglobulins (Igs) via interactions of its N-terminal and internal regions with the Fab region of Igs. Therefore, HRF together with HRF-reactive IgE can activate mast cells in vitro. The Ig-interacting HRF peptides that block HRF-Ig interactions can inhibit IgE+HRF-induced mast cell activation and in vivo cutaneous anaphylaxis and airway inflammation. Intranasally administered HRF can recruit inflammatory immune cells to the lung in naïve mice in a mast cell- and Fc receptor-dependent manner. These results strongly suggest the proinflammatory role of HRF in asthma and skin immediate hypersensitivity. A total of 6 samples were analyzed; wild type C57BL/6, FcRg KO and FceRIa KO mice were challenged with PBS (control) or mouse histamien-releasing factor
Project description:Immunoglobulin (Ig) E-mediated activation of mast cells and basophils underlies allergic diseases such as asthma. Histamine-releasing factor (HRF), also known as translationally controlled tumor protein (TCTP) and fortilin, is a highly conserved protein with both intracellular and extracellular functions. Secreted HRF can stimulate histamine release and IL-4 and IL-13 production from IgE-sensitized basophils and mast cells. HRF is found in nasal, skin blister and bronchoalveolar lavage (BAL) fluids during late-phase allergic reactions (LPRs), which implicates HRF in the LPR and chronic allergic inflammation. Here we identify a subset of IgE and IgG antibodies as HRF-interacting molecules. HRF can exist as a dimer and bind to immunoglobulins (Igs) via interactions of its N-terminal and internal regions with the Fab region of Igs. Therefore, HRF together with HRF-reactive IgE can activate mast cells in vitro. The Ig-interacting HRF peptides that block HRF-Ig interactions can inhibit IgE+HRF-induced mast cell activation and in vivo cutaneous anaphylaxis and airway inflammation. Intranasally administered HRF can recruit inflammatory immune cells to the lung in naïve mice in a mast cell- and Fc receptor-dependent manner. These results strongly suggest the proinflammatory role of HRF in asthma and skin immediate hypersensitivity.
Project description:Understanding the transcriptional signature of IgE producing cells is fundamental to plasma cell biology. IgE PCs from bone marrow (BM) upregulated genes associated with pro-survival, and BM homing, whereas IgE PCs from draining lymph nodes (dLN) expressed genes associated with recent class-switching and differenatiation. Finally, IgE PCs exhibited higher expression of ER stress and protein coding compared to IgG1.
Project description:IgE plays an essential role in the pathogenesis of allergies and its production is strongly regulated. A transient IgE germinal center phase and lack of IgE memory cells limit the generation of pathogenic IgE, but this can be overcome by sequential switching of IgG1 cells to IgE. We investigated which population of IgG1 cells can give rise to IgE-producing cells in memory responses. We identified three populations of IgG1 memory B cells (DP:CD73+CD80+, SP:CD73-CD80+, DN:CD73-CD80-) that generate IgE plasma cells of high or low affinity, but none gives rise to IgE germinal center cells or IgE memory cells. The two memory IgG1 populations differ however in their ability to differentiate into IgG1 plasma cells and germinal center cells, and to expand the IgG1 memory B cell pool. To explore the molecular mechanisms that may explain the distinct functions of IgG1 memory B cell subsets we compared their expression by transcriptome analysis using next generation sequencing.
Project description:The mechanisms involved in the maintenance of memory IgE responses are poorly understood, and the role played by germinal center (GC) IgE cells in these memory responses is particularly unclear. IgE B-cell differentiation is characterized by a transient GC phase, a bias towards the plasma cell (PC) fate, and dependence on sequential switching for the production of high-affinity IgE. We show here that IgE GC B cells are unfit to undergo the conventional GC differentiation program due to impaired B-cell receptor function and increased apoptosis. IgE GC cells fail to populate the GC light zone and are unable to contribute to the memory and long-lived PC compartments. Furthermore, we demonstrate that direct and sequential switching are linked to distinct B-cell differentiation fates: direct switching generates IgE GC cells, whereas sequential switching gives rise to IgE plasma cells. We propose a comprehensive model for the generation and memory of IgE responses. The purpose of this analysis was to: 1) identify expression differences between IgE and IgG1 B lymphocytes, 2) identify GC Dark Zone (DZ) and Light Zone (LZ) signatures of IgG1 GC cells. For that purpose, we compared in one experiment the gene expression patterns of IgE germinal center (GC) cells, IgG1 GC cells, IgE plasma cells (PC), IgG1 PC and naïve cells. In a second experiment, we compared the expression of IgG1 DZ GC cells with that of IgG1 LZ GC cells. Triplicates obtained from independent sorting experiments were used for all samples except two (IgG1 PC=2 samples; IgE PC=4 samples). Each sample was obtained from a pool of three individual mice. The mice used in the experiment were CeGFP BALB/c mice infected with the parasite N. brasiliensis. CeGFP mice carry an IRES-GFP KI cassette in the 3'UTR of membrane IgE. In these mice, GFP expression marks IgE cells, and a population of IgG1 cells with a rearrangement to Cepsilon in the non-productive (VDJ negative) IgH chromosome.
Project description:The transcriptional response to egg differed between PBMCs from egg allergic and clinically tolerant subjects. Differentially expressed genes included IL-9 and TNFg. Enrichment analysis of differentially expressed gene signatures and associated co-expressed gene modules revealed an association of egg allergy with unique immune pathways. In addition to showing a positive association of egg-induced gene transcription in allergic individuals with Th2 CD4+ T cells and a novel negative association with induced Tregs, this approach identified a highly significant overlap with genes induced by TLR4 stimulation of myeloid cells.