Project description:Tissue and microbial cues regulate the abundance and function of CD8+ T cells at barrier sites, yet the impact of specific microbes on their long-term durability remains unclear. Here, we show that the commensal protist Tritrichomonas musculus (T. mu) depletes intestinal CD8+ T cells, particularly tissue resident memory (TRM) cells, through activation of localized type 2 immunity. Colonization with T. mu or administration of its major secreted metabolite, succinate, led to the rapid decline of intestinal CD8+ T cells but left systemic memory T cells unaffected. The purinergic receptor, P2RX7, is highly expressed by intestinal TRMs and chemical antagonism of this receptor markedly restored CD8+ T cells during succinate feeding. Using lymphocytic choriomeningitis virus (LCMV) infection to track antigen-specific CD8+ memory T cells, we found viral-specific CD8+ TRMs repopulate the intestine independent of LCMV reinfection after removal of succinate treatment. These findings highlight how commensal protists and their metabolites reset homeostatic CD8+ T cell carrying capacity through damage-independent stimulation of TRM apoptosis and regulate mucosal memory.
Project description:The ocular surface is colonized by commensal microbiota, which tune the local mucosal immune response. However, the mechanisms underlying the induction of an IL-17 response by γδ T cells in response to ocular commensal bacteria, particularly Corynebacterium mastitidis (C. mast), have not been fully investigated. Here, we demonstrated that intrinsic TLR2 activation in γδ T cells by commensal microbiota is required for their IL-17A production and fatty acid oxidation. We also identified IκBζ, a transcription factor whose expression is upregulated by TLR2 signaling, as a key regulator to enhance the expression of genes responsible for IL-17A production and FAO program. This study highlights the role of TLR2-mediated transcriptional regulation in targeting effector cytokines and metabolic programs to support IL-17A responses to commensal bacteria.
Project description:The ocular surface is colonized by commensal microbiota, which tune the local mucosal immune response. However, the mechanisms underlying the induction of an IL-17 response by γδ T cells in response to ocular commensal bacteria, particularly Corynebacterium mastitidis (C. mast), have not been fully investigated. Here, we demonstrated that intrinsic TLR2 activation in γδ T cells by commensal microbiota is required for their IL-17A production and fatty acid oxidation. We also identified IκBζ, a transcription factor whose expression is upregulated by TLR2 signaling, as a key regulator to enhance the expression of genes responsible for IL-17A production and FAO program. This study highlights the role of TLR2-mediated transcriptional regulation in targeting effector cytokines and metabolic programs to support IL-17A responses to commensal bacteria.
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).
Project description:Commensal bacteria influence host physiology, including immune responses, without invading host tissues. We show that proteins from segmented filamentous bacteria (SFB), which are immunomodulatory commensal microbes, are transferred into intestinal epithelial cells by adhesion-directed endocytosis that is distinct from the clathrin-dependent endocytosis of invasive pathogens. SFB transfer microbial cell wall-associated proteins, including an antigen that stimulates mucosal Th17 cell differentiation, into the cytosol of epithelial cells. Removal of CDC42 activity in vivo led to disruption of endocytosis induced by SFB, decreased epithelial antigen acquisition with consequent loss of immune modulation by SFB-specific CD4 T cells and mucosal Th17 cells. Our findings indicate direct communication between a resident gut microbe and the host and show that intestinal epithelial cells acquire antigens from commensal bacteria for generation of T-cell responses to the resident microbiota.
Project description:Leber2015 - Mucosal immunity and gut
microbiome interaction during C. difficile infection
This model is described in the article:
Systems Modeling of
Interactions between Mucosal Immunity and the Gut Microbiome
during Clostridium difficile Infection.
Leber A, Viladomiu M, Hontecillas R,
Abedi V, Philipson C, Hoops S, Howard B, Bassaganya-Riera
J.
PLoS ONE 2015; 10(7): e0134849
Abstract:
Clostridium difficile infections are associated with the use
of broad-spectrum antibiotics and result in an exuberant
inflammatory response, leading to nosocomial diarrhea, colitis
and even death. To better understand the dynamics of mucosal
immunity during C. difficile infection from initiation through
expansion to resolution, we built a computational model of the
mucosal immune response to the bacterium. The model was
calibrated using data from a mouse model of C. difficile
infection. The model demonstrates a crucial role of T helper 17
(Th17) effector responses in the colonic lamina propria and
luminal commensal bacteria populations in the clearance of C.
difficile and colonic pathology, whereas regulatory T (Treg)
cells responses are associated with the recovery phase. In
addition, the production of anti-microbial peptides by inflamed
epithelial cells and activated neutrophils in response to C.
difficile infection inhibit the re-growth of beneficial
commensal bacterial species. Computational simulations suggest
that the removal of neutrophil and epithelial cell derived
anti-microbial inhibitions, separately and together, on
commensal bacterial regrowth promote recovery and minimize
colonic inflammatory pathology. Simulation results predict a
decrease in colonic inflammatory markers, such as neutrophilic
influx and Th17 cells in the colonic lamina propria, and length
of infection with accelerated commensal bacteria re-growth
through altered anti-microbial inhibition. Computational
modeling provides novel insights on the therapeutic value of
repopulating the colonic microbiome and inducing regulatory
mucosal immune responses during C. difficile infection. Thus,
modeling mucosal immunity-gut microbiota interactions has the
potential to guide the development of targeted fecal
transplantation therapies in the context of precision medicine
interventions.
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BIOMD0000000583.
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To the extent possible under law, all copyright and related or
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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.