Project description:Th17 cells play a role as an inflammation mediator in a variety of autoimmune disorders, including inflammatory bowel disease (IBD) and thus are widely considered to be pathogenic. However, Th17 cells are present in the normal intestine and show a homeostatic phenotype, i.e., they participate in the maintenance of intestinal homeostasis rather than inducing inflammation. We observed an enlarged Th17 population in the small intestine of C57BL/6.IgA-/- mice compared to wild-type mice, which was further amplified with cholera toxin (CT) immunization without causing intestinal inflammation. The increased Th17 induction and the correspondingly 10-fold higher CTB-specific serum IgG response in C57BL/6.IgA-/- mice after CT immunization was microbiota dependent and was associated with increased segmented filamentous bacteria (SFB) in the small intestine of C57BL/6.IgA-/- mice. Oral administration of vancomycin greatly dampened both CT immunogenicity and adjuvanticity, and the differential CT responses in IgA-/- and wild-type mice disappeared after intestinal microbiota equalization. Using gnotobiotic mouse models, we found that CT induction of homeostatic intestinal Th17 responses was supported not only by SFB but also by other commensal bacteria. Furthermore, transcriptome analysis using IL-17AhCD2 reporter mice revealed a similar gene expression profile in CT-induced intestinal Th17 cells and endogenous intestinal Th17 cells at homeostasis, with upregulated expressions of a panel of immune regulatory genes, which was distinctly different from the gene expression profile of pathogenic Th17 cells. Taken together, we identified a non-pathogenic signature of intestinal homeostatic Th17 cells, which are actively regulated by the commensal microbiota and can be selectively stimulated by CT.

2017-08-31 | GSE97571 | GEO

Altered mucosal homeostasis in mice lacking secretory antibodies

Project description:The mammalian gut is inhabited by a large and complex microbial community that lives in a mutualistic relationship with its host. Innate and adaptive mucosal defense mechanisms ensure a homeostatic relationship with this commensal microbiota. Secretory antibodies are generated from the active polymeric Ig receptor (pIgR)-mediated transport of IgA and IgM antibodies to the gut lumen and form the first line of adaptive immune defense of the intestinal mucosa. We probed mucosal homeostasis in pIgR knockout (KO) mice, which lack secretory antibodies. We found that in pIgR KO mice, colonic epithelial cells, the cell type most closely in contact with intestinal microbes, differentially expressed (>2-fold change) more than 200 genes compared with wild type mice, and upregulated the expression of anti-microbial peptides in a commensal-dependent manner. Detailed profiling of microbial communities based on 16S rRNA genes revealed differences in the commensal microbiota between pIgR KO and wild type mice. Furthermore, we found that pIgR KO mice showed increased susceptibility to dextran sulfate sodium (DSS)-induced colitis, and that this was driven by their conventional intestinal microbiota. In conclusion, secretory antibodies or the pIgR itself are required to maintain a stable commensal microbiota. In the absence of these humoral effector components, gut homeostasis is disturbed and the outcome of colitis significantly worsened. 4 groups: wild type mice treated with antibiotic (5 replicates), wild type mice left untreated (5 replicates), pIgR KO mice treated with antibiotic (6 replicates), and pIgR KO mice left untreated (6 replicates).

2013-12-28 | E-GEOD-34630 | biostudies-arrayexpress

Peyer’s patches are required for Bacteroides fragilis to induce protective systemic IgA

Project description:Gut-educated IgA-secreting plasma cells that disseminate beyond the mucosa and into systemic tissues can help prevent disease in several contexts. Here we show, the commensal bacteria Bacteroides fragilis (Bf), is an efficient inducer of systemic IgA responses. The generation of bone marrow IgA plasma cells and high levels of serum IgA specific to Bf requires robust intestinal colonization. Bf-specific IgA responses were severely diminished in mice lacking Peyer’s patches, but not mice lacking a cecal patch. Colonization resulted in few changes in the host transcriptional profile in the gut, suggesting a commensal relationship. High levels of Bf-specific serum IgA, but not IgG, provided protection from peritoneal abscess formation in a bowel perforation model of Bf dissemination. These findings demonstrate a critical role for bacterial colonization and Peyer’s patches in the induction of robust systemic IgA responses that confer protection from bacterial dissemination originating from the gut.

2024-07-25 | GSE272717 | GEO

Commensal microbes drive the generation of large numbers of bone marrow plasma cells

Project description:The mechanisms whereby enteric pathogens and microbes induce systemic antibody responses remain obscure. In contrast to accepted models, we show that commensal microbes have a dramatic impact on the bone marrow (BM) plasma cell pool. Unlike standard vendor mice, in mice reared in our colony the majority of long-lived BM plasma cells secreted IgA antibodies. Exposing vendor mice to a unique microflora or Helicobacter sp. led to the generation of IgA-secreting BM cells, while also inducing increases in serum IgA antibodies enriched for binding to several commensal bacterial taxa. Moreover, BM IgA-secreting plasma cells exhibited a common clonal ancestry with intestinal IgA+ plasma cells, and both populations possessed unique gene expression signatures compared to other long-lived BM plasma cells. We conclude that commensal microbes overtly influence the BM plasma cell pool, and suggest that select commensal microbes can facilitate the induction of systemic humoral immunity.

2018-07-01 | GSE87091 | GEO

Altered mucosal homeostasis in mice lacking secretory antibodies

2013-12-28 | GSE34630 | GEO

Peyer's Patch BCR repertoire analysis in mice lacking H2-Ab1 on intestinal epithelial cells

Project description:Intestinal epithelial cells (IEC) express large amounts of major histocompatibility complex II (MHCII) molecules. Despite this long-appreciated observation, the function of epithelial MHCII-mediated signaling on gut homeostasis remains enigmatic. As IECs serve as the primary cellular barrier between intestinal microbes and underlying host immune cells, we reasoned that IEC-intrinsic antigen presentation may play a role in tolerogenic responses towards the microbiota. Mice with an IEC-intrinsic defect in MHCII expression (IECΔMHCII) develop elevated T cell-dependent IgA responses, but a reduction in microbiota responsive regulatory T cells (Tregs). Despite elevated IgA levels in IECΔMHCII mice, immunoglobulin repertoires exhibit less selection and IgA has reduced reactivity to the microbiota, which is associated with increased inter-individual variability in microbiota composition. Consistent with reductions in microbiota-responsive Tregs, IECΔMHCII mice develop worsened colitis. A striking difference observed in the absence of IEC-MHCII is that while transcription of MHCII is similar, underlying mononuclear phagocytes had reduced surface MHCII. Macrophages were found to be capable of acquiring MHCII molecules from IECs, and macrophages isolated from IECΔMHCII mice had decreased capacity to stimulate Treg development. Thus, epithelial-myeloid interactions govern development of adaptive responses to microbial antigens within the gastrointestinal tract.

2021-09-09 | GSE183711 | GEO

Small intestinal immune cell distributions and transcriptomes in mice lacking H2-Ab1 on intestinal epithelial cells.

2021-09-09 | GSE183710 | GEO