Project description:BackgroundB cells expressing IgE contribute to immunity against parasites and venoms and are the source of antigen specificity in allergic patients, yet the developmental pathways producing these B cells in human subjects remain a subject of debate. Much of our knowledge of IgE lineage development derives from model studies in mice rather than from human subjects.ObjectiveWe evaluate models for isotype switching to IgE in human subjects using immunoglobulin heavy chain (IGH) mutational lineage data.MethodsWe analyzed IGH repertoires in 9 allergic and 24 healthy adults using high-throughput DNA sequencing of 15,843,270 IGH rearrangements to identify clonal lineages of B cells containing members expressing IgE. Somatic mutations in IGH inherited from common ancestors within the clonal lineage are used to infer the relationships between B cells.ResultsData from 613,641 multi-isotype B-cell clonal lineages, of which 592 include an IgE member, are consistent with indirect switching to IgE from IgG- or IgA-expressing lineage members in human subjects. We also find that these inferred isotype switching frequencies are similar in healthy and allergic subjects.ConclusionsWe found evidence that secondary isotype switching of mutated IgG1-expressing B cells is the primary source of IgE in human subjects, with lesser contributions from precursors expressing other switched isotypes and rarely IgM or IgD, suggesting that IgE is derived from previously antigen-experienced B cells rather than naive B cells that typically express low-affinity unmutated antibodies. These data provide a basis from which to evaluate allergen-specific human antibody repertoires in healthy and diseased subjects.
Project description:Bone marrow plasma cells (BMPCs) produce durable, infection-resistant IgM, IgG, and IgA antibodies, but in some cases, pro-allergic IgE. Despite this, BMPC sources are unclear. We charted single BMPC transcriptional and clonal heterogeneity in peanut-allergic and non-allergic humans across CD19 protein expression—due to CD19’s inverse correlation to BMPC longevity. Transcriptional and clonal diversity revealed distinct functional modules. Additionally, distributions of somatic hypermutation and intraclonal antibody sequence variance suggest CD19low and CD19high BMPCs arise from recalled memory and germinal center B cells, respectively. Most IgE BMPCs were from peanut-allergic individuals; some bound peanut and potently prevented peanut-driven anaphylaxis in a mouse model. These findings shed light on BMPC origins and identify the bone marrow as a likely source for long-lived pathogenic IgE in peanut allergy.
Project description:Allergy is one of the most prevalent chronic diseases, affecting hundreds of millions of people worldwide. In allergy, environmental allergens induce B cells to undergo class switch recombination and produce Immunoglobulin E (IgE) antibodies. IgE is a key molecule that mediates allergic responses by coating mast cell or basophil surfaces and inducing degranulation upon binding a specific allergen. IgE can also be spontaneously produced in the absence of exogenous allergens, yet the origin, regulation, and functions of such “natural” IgE still remains largely unknown. Here, we discovered that glucocorticoids, which are steroid stress hormones, enhance IgE isotype class switching in B cells both in vivo and ex vivo without antigenic challenge. Such IgE class switching is promoted by B cell-intrinsic glucocorticoid receptor signaling that reinforces CD40 signaling and synergizes with the IL-4/STAT6 pathway. In addition, we found that rare B cells in the mesenteric lymph nodes are responsible for the production of glucocorticoid-inducible IgE. Furthermore, we showed that locally produced glucocorticoids in the gut may induce natural IgE during perturbations of gut homeostasis such as dysbiosis. Notably, mice preemptively treated with glucocorticoids were protected from subsequent IgE-mediated pathogenic anaphylaxis in vivo. Together, our results suggest that glucocorticoids, classically considered to be broadly immunosuppressive, have a selective immunostimulatory role in B cells.
Project description:'Non-coding transcripts originating upstream of the immunoglobulin constant region (I-transcripts) are required to direct activation-induced deaminase to initiate class switching in B cells. Differential regulation of I and I1 transcription in response to interleukin-4 (IL-4), hence class switching to IgE and IgG1, is not fully understood. Here we combine novel mouse reporters and single-cell RNA-seq to reveal the heterogeneity in IL-4 induced I-transcription. Transgenic mice were generated with one allele labelled with an eGFP fluorescent reporter gene in the first exon of the gamma-1 non-coding RNA and one allele with a tdTom fluorescent reporter gene in the first exon of the epsilon non-coding RNA. Ex vivo splenic B cells from these mice were stimulated with IL-4, lipopolysaccharide and B cell activating factor. After 24 hours culture, cell were sorted according to their fluorescence and used for single-cell mRNA-sequencing. Two independent experiments were performed (labelled as ''batch 1'' and ''batch 2'').'
Project description:We use polyclonal Ighγ1/γ1 and Ighε/ε mice (which initially produce only IgG1 or IgE from their respective native genomic configurations) to examine the role of IgH isotype on BCR function. We use microarray expression analysis to compare the internal state of the three IgH isotype specific B-cells. Microarray was used to compare the expression level of various genes in splenic follicular B-cells of Ighε/ε, Ighγ1/γ1 and Ighwt mice. Each mouse strain also had a naturally pre-assembled Ig light chain (VJk5).
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 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.