Feedback control of AHR signalling regulates intestinal immunity

The aryl hydrocarbon receptor (AHR) recognizes xenobiotics as well as natural compounds such as tryptophan metabolites, dietary components and microbiota-derived factors, and it is important for maintenance of homeostasis at mucosal surfaces. AHR activation induces cytochrome P4501 (CYP1) enzymes, which oxygenate AHR ligands, leading to their metabolic clearance and detoxification. Thus, CYP1 enzymes have an important feedback role that curtails the duration of AHR signalling, but it remains unclear whether they also regulate AHR ligand availability in vivo. Here we show that dysregulated expression of Cyp1a1 in mice depletes the reservoir of natural AHR ligands, generating a quasi AHR-deficient state. Constitutive expression of Cyp1a1 throughout the body or restricted specifically to intestinal epithelial cells resulted in loss of AHR-dependent type 3 innate lymphoid cells and T helper 17 cells and increased susceptibility to enteric infection. The deleterious effects of excessive AHR ligand degradation on intestinal immune functions could be counter-balanced by increasing the intake of AHR ligands in the diet. Thus, our data indicate that intestinal epithelial cells serve as gatekeepers for the supply of AHR ligands to the host and emphasize the importance of feedback control in modulating AHR pathway activation

Epithelial-Cell-Derived Phospholipase A2 Group 1B Is an Endogenous Anthelmintic.

Immunity to intestinal helminth infections has been well studied, but the mechanism of helminth killing prior to expulsion remains unclear. Here we identify epithelial-cell-derived phospholipase A2 group 1B (PLA2g1B) as a host-derived endogenous anthelmintic. PLA2g1B is elevated in resistant mice and is responsible for killing tissue-embedded larvae. Despite comparable activities of other essential type-2-dependent immune mechanisms, Pla2g1b-/- mice failed to expel the intestinal helminths Heligmosomoides polygyrus or Nippostrongylus brasiliensis. Expression of Pla2g1b by epithelial cells was dependent upon intestinal microbiota, adaptive immunity, and common-gamma chain-dependent signaling. Notably, Pla2g1b was downregulated in susceptible mice and inhibited by IL-4R-signaling in vitro, uncoupling parasite killing from expulsion mechanisms. Resistance was restored in Pla2g1b-/- mice by treating infective H. polygyrus L3 larvae with PLA2g1B, which reduced larval phospholipid abundance. These findings uncover epithelial-cell-derived Pla2g1b as an essential mediator of helminth killing, highlighting a previously overlooked mechanism of anti-helminth immunity

L’interféron de type I et les cellules régulatrices : les effets sur le développement, l’homéostasie et la fonction

Type I Interferons (IFNs) are a family of cytokines with antiviral and immunomodulatory properties. While the antiviral effects of IFNs are well characterized, their immunomodulatory properties are less clear. We examined the effects of type I IFN on development, homeostasis, and function of Treg cells. We used mixed bone marrow (BM) chimeras between WT and IFNαβ receptor (IFNAR) KO mice, and heterozygous female mice expressing a Treg-specific deletion of the IFNAR. IFNAR signaling promoted the development of the Treg lineage in the thymus and their survival in the periphery. IFNAR KO Treg from chimeric mice displayed a more naïve phenotype. In mixed chimeras with Scurfy fetal liver, Treg derived from IFNAR KO BM were unable to control T effector cell activation and tissue inflammation. We also examined the potential effects during Chronic Lymphocytic Choriomeningitis Virus infection. We demonstrated that the percentage of Vβ5+ Treg was significantly reduced in IFNAR KO mice, and that the IFNAR functions in a Treg cell intrinsic manner. We also studied the effect during Experimental autoimmune encephalomyelitis (EAE). Following induction of EAE, WT / IFNAR KO chimeras develop more severe disease than the WT/WT chimeras. Mice with a conditional deletion of the IFNAR in Treg rapidly developed a very severe form of EAE. These results demonstrate that signaling via the IFNAR is required for Treg suppressor function in EAE. Collectively, these studies demonstrate that under certain condition including stress, chronic infection, and autoimmune disease, IFNAR signaling is essential to maintain Treg development, homeostasis, and function.L'interféron de type I (IFN) est une famille de cytokine avec des propriétés antivirales et immunomodulatrices. Alors que les effets antiviraux de l'IFN sont bien caractérisés, leurs propriétés immunomodulatrices le sont moins. Nous avons examiné en profondeur les effets de l'IFN de type I sur le développement, l'homéostasie, et la fonction des cellules Treg. Nous avons utilisé des souris chimériques reconstituées avec une mixture de moelle osseuse de souris normale (WT) et de souris sans le récepteur de l'IFN(IFNAR)KO, et des souris femelles hétérozygotes exprimant une délétion d'IFNAR spécifiquement sur les Treg. Dans ces deux modèles, la signalisation d'IFNAR favorise le développement de la lignée Treg dans le thymus et leur survie dans la périphérie. Nous avons également généré des souris chimériques en utilisant le foie f¿tal de souris scurfy, les Treg dérivés de IFNAR KO ont été incapables de contrôler l'activation des cellules T effectrices et l'inflammation des tissus. Nous avons aussi examiné les effets pendant l'infection avec le virus chorioméningite lymphocytaire chronique (LCMV). Nous avons démontré que le pourcentage de V?5+ Treg était significativement réduit chez les souris IFNAR KO. Nous avons également examiné l'effet pendant Encéphalomyélite auto-immune expérimentale (EAE). Suite à l'induction de l'EAE, les souris chimériques WT/IFNAR KO développent une maladie plus sévère que les souris WT/WT. Nous montrons aussi que les souris avec une délétion conditionnelle de IFNAR dans les Tregs développent une forme très grave de l'EAE. Ces résultats démontrent que la signalisation via IFNAR est nécessaire pour la fonction de suppressive des Treg dans l'EAE

Type I interferon signaling attenuates regulatory T cell function in viral infection and in the tumor microenvironment

<div><p>Regulatory T cells (Tregs) play a cardinal role in the immune system by suppressing detrimental autoimmune responses, but their role in acute, chronic infectious diseases and tumor microenvironment remains unclear. We recently demonstrated that IFN-α/β receptor (IFNAR) signaling promotes Treg function in autoimmunity. Here we dissected the functional role of IFNAR-signaling in Tregs using Treg-specific IFNAR deficient (IFNAR^fl/flxFoxp3^YFP-Cre) mice in acute LCMV Armstrong, chronic Clone-13 viral infection, and in tumor models. In both viral infection and tumor models, IFNAR^fl/flxFoxp3^YFP-Cre mice Tregs expressed enhanced Treg associated activation antigens. LCMV-specific CD8⁺ T cells and tumor infiltrating lymphocytes from IFNAR^fl/flxFoxp3^YFP-Cre mice produced less antiviral and antitumor IFN-γ and TNF-α. In chronic viral model, the numbers of antiviral effector and memory CD8⁺ T cells were decreased in IFNAR^fl/flxFoxp3^YFP-Cre mice and the effector CD4⁺ and CD8⁺ T cells exhibited a phenotype compatible with enhanced exhaustion. IFNAR^fl/flxFoxp3^YFP-Cre mice cleared Armstrong infection normally, but had higher viral titers in sera, kidneys and lungs during chronic infection, and higher tumor burden than the WT controls. The enhanced activated phenotype was evident through transcriptome analysis of IFNAR^fl/flxFoxp3^YFP-Cre mice Tregs during infection demonstrated differential expression of a unique gene signature characterized by elevated levels of genes involved in suppression and decreased levels of genes mediating apoptosis. Thus, IFN signaling in Tregs is beneficial to host resulting in a more effective antiviral response and augmented antitumor immunity.</p></div

Absence of IFNAR signaling in Tregs results in enhanced virus-specific T cell exhaustion.

<p>(<b>A</b> and <b>B</b>) Kinetics of PD1 expression was shown on gated CD8⁺ and CD4⁺Foxp3^- T cells during chronic LCMV infection. (<b>C</b> and <b>D</b>) Percentage and total numbers of PD1⁺ EOMES⁺ cells among gated CD8⁺ and CD4⁺Foxp3^- T cells were plotted from days 25, and 46 Cl-13 infected mice. (<b>E</b> and <b>F</b>) PD1⁺CD39⁺ cells frequencies and numbers were estimated within CD8⁺ T and CD4⁺Foxp3^- T cells from day 46 Cl-13 infected mice. (<b>G</b> and <b>H</b>) PD1 expression was evaluated within CD8⁺CD44⁺GP33 and CD8⁺CD44⁺GP276 Tet⁺ T cells from Cl-13 infected mice on indicated days. * <i>P</i> < 0.05, ** <i>P</i> < 0.01, and *** <i>P</i> < 0.001 (unpaired two-tailed Student’s <i>t</i>-test). Data represent from two to five experiments (<b>A</b> and <b>B</b>), representative of two experiments (<b>C-H</b>), on indicated days with three to four mice per group in each experiment (Mean±SEM).</p

Transcriptome analysis of Foxp3⁺ Tregs from LCMV infected Treg-specific IFNAR-deficient mice.

<p>(<b>A</b>) PCA was performed on day 5 LCMV Armstrong infected Foxp3^YFP-Cre and IFNAR^fl/fl x Foxp3^YFP-Cre mice sorted CD4⁺YFP⁺ Treg cells RNA-seq samples (4 samples in each group). (<b>B</b>) Scatter plot showing the comparison of global gene expression profiles of Tregs between Armstrong infected Foxp3^YFP-Cre and IFNAR^fl/fl x Foxp3^YFP-Cre mice. Total of 586 genes were significantly differentially expressed and colored, 249 genes (red) were down regulated, and 337 genes (blue) upregulated in IFNAR^fl/fl x Foxp3^YFP-Cre mice (fold change 1.5 and above, adjusted <i>P</i> < 0.05). (<b>C</b>) GSEA for non-IFN related genes, showing enrichment plot for natural Treg vs. T conv DN gene set (36 out 42 genes were enriched in core, Enrichment score: 0.566, <i>P</i> < 0.01, FDR: 0.0) with positive enrichment in IFNAR^fl/fl x Foxp3^YFP-Cre mice Tregs relative to Foxp3^YFP-Cre mice Tregs. (<b>D</b>) Heat map showing the significant differential expression of 32 Treg-signature genes (fold change 1.5 and above, adjusted <i>P</i> < 0.05), as previously reported [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006985#ppat.1006985.ref049" target="_blank">49</a>, <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1006985#ppat.1006985.ref050" target="_blank">50</a>], differentially expressed genes were normalized by z-score. (<b>E</b>) PCA was performed on day 25 LCMV Cl-13 infected Foxp3^YFP-Cre and IFNAR^fl/fl x Foxp3^YFP-Cre mice sorted CD4⁺YFP⁺ Treg cells RNA-seq samples (5 samples in each group). (<b>F</b>) Scatter plot showing the comparison of global gene expression profiles of Tregs between Cl-13 infected Foxp3^YFP-Cre and IFNAR^fl/fl x Foxp3^YFP-Cre mice. Total of 36 genes were significantly differentially expressed and colored, 23 genes (red) were down regulated, and 13 genes (blue) upregulated in IFNAR^fl/fl x Foxp3^YFP-Cre mice (fold change 1.5 and above, adjusted <i>P</i> < 0.05). (<b>G</b>) Heat map showing the significant differential expression of 22 non-IFN related genes (fold change 1.5 and above, adjusted <i>P</i> < 0.05, normalized by z-score). (<b>H</b>) Heat map showing the significant differential expression of 14 genes from LCMV Armstrong infected Foxp3^YFP-Cre mice and IFNAR^fl/fl x Foxp3^YFP-Cre mice Tregs, which were in consistent with transcriptome from LCMV Cl-13 infected mice Tregs (fold change 1.5 and above, adjusted <i>P</i> < 0.05, normalized by z-score). Armstrong infection transcriptome data obtained from an experiment involving four mice per group (<b>A-D</b> and <b>H</b>), and transcriptome data from Cl-13 infection, involved an experiment with five mice per group (<b>E-G</b>).</p