• Transmaternal Helicobacter pylori exposure reduces allergic airway inflammation in offspring through regulatory T cells.

      Kyburz, Andreas; Fallegger, Angela; Zhang, Xiaozhou; Altobelli, Aleksandra; Artola-Boran, Mariela; Borbet, Timothy; Urban, Sabine; Paul, Petra; Münz, Christian; Floess, Stefan; et al. (Elsevier, 2018-09-19)
      Background: Transmaternal exposure to tobacco, microbes, nutrients, and other environmental factors shapes the fetal immune system through epigenetic processes. The gastric microbe Helicobacter pylori represents an ancestral constituent of the human microbiota that causes gastric disorders on the one hand and is inversely associated with allergies and chronic inflammatory conditions on the other. Objective: Here we investigate the consequences of transmaternal exposure to H pylori in utero and/or during lactation for susceptibility to viral and bacterial infection, predisposition to allergic airway inflammation, and development of immune cell populations in the lungs and lymphoid organs. Methods: We use experimental models of house dust mite- or ovalbumin-induced airway inflammation and influenza A virus or Citrobacter rodentium infection along with metagenomics analyses, multicolor flow cytometry, and bisulfite pyrosequencing, to study the effects of H pylori on allergy severity and immunologic and microbiome correlates thereof. Results: Perinatal exposure to H pylori extract or its immunomodulator vacuolating cytotoxin confers robust protective effects against allergic airway inflammation not only in first- but also second-generation offspring but does not increase susceptibility to viral or bacterial infection. Immune correlates of allergy protection include skewing of regulatory over effector T cells, expansion of regulatory T-cell subsets expressing CXCR3 or retinoic acid-related orphan receptor γt, and demethylation of the forkhead box P3 (FOXP3) locus. The composition and diversity of the gastrointestinal microbiota is measurably affected by perinatal H pylori exposure. Conclusion: We conclude that exposure to H pylori has consequences not only for the carrier but also for subsequent generations that can be exploited for interventional purposes. Keywords: Allergic airway inflammation; epigenetic regulation of allergy and asthma; immune regulation; immune tolerance; metagenomics; microbial interventions during pregnancy.
    • Intact interleukin-10 receptor signaling protects from hippocampal damage elicited by experimental neurotropic virus infection of SJL mice.

      Uhde, Ann-Kathrin; Ciurkiewicz, Malgorzata; Herder, Vanessa; Khan, Muhammad Akram; Hensel, Niko; Claus, Peter; Beckstette, Michael; Teich, René; Floess, Stefan; Baumgärtner, Wolfgang; et al. (2018-04-17)
      Theiler's murine encephalomyelitis virus (TMEV) infection represents an experimental mouse model to study hippocampal damage induced by neurotropic viruses. IL-10 is a pleiotropic cytokine with profound anti-inflammatory properties, which critically controls immune homeostasis. In order to analyze IL-10R signaling following virus-induced polioencephalitis, SJL mice were intracerebrally infected with TMEV. RNA-based next generation sequencing revealed an up-regulation of Il10, Il10rα and further genes involved in IL-10 downstream signaling, including Jak1, Socs3 and Stat3 in the brain upon infection. Subsequent antibody-mediated blockade of IL-10R signaling led to enhanced hippocampal damage with neuronal loss and increased recruitment of CD3+ T cells, CD45R+ B cells and an up-regulation of Il1α mRNA. Increased expression of Tgfβ and Foxp3 as well as accumulation of Foxp3+ regulatory T cells and arginase-1+ macrophages/microglia was detected in the hippocampus, representing a potential compensatory mechanism following disturbed IL-10R signaling. Additionally, an increased peripheral Chi3l3 expression was found in spleens of infected mice, which may embody reactive regulatory mechanisms for prevention of excessive immunopathology. The present study highlights the importance of IL-10R signaling for immune regulation and its neuroprotective properties in the context of an acute neurotropic virus infection.
    • The invasin D protein fromYersinia pseudotuberculosisselectively binds the Fab region of host antibodies and affects colonization of the intestine.

      Sadana, Pooja; Geyer, Rebecca; Pezoldt, Joern; Helmsing, Saskia; Huehn, Jochen; Hust, Michael; Dersch, Petra; Scrima, Andrea; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2018-03-13)
      Yersinia pseudotuberculosis is a Gram-negative bacterium and zoonotic pathogen responsible for a wide range of diseases, ranging from mild diarrhea, enterocolitis, lymphatic adenitis to persistent local inflammation. TheY. pseudotuberculosisinvasin D (InvD) molecule belongs to the invasin (InvA)-type autotransporter proteins, but its structure and function remain unknown. In this study, we present the first crystal structure of InvD, analyzed its expression and function in a murine infection model, and identified its target molecule in the host. We found that InvD is induced at 37°C and expressed in vivo2-4 days after infection, indicating that InvD is a virulence factor. During infection, InvD was expressed in all parts of the intestinal tract, but not in deeper lymphoid tissues. The crystal structure of the C-terminal adhesion domain of InvD revealed a distinct Ig-related fold, that, apart from the canonical β-sheets, comprises various modifications of and insertions into the Ig-core structure. We identified the Fab fragment of host-derived IgG/IgA antibodies as the target of the adhesion domain. Phage display panning and flow cytometry data further revealed that InvD exhibits a preferential binding specificity toward antibodies with VH3/VK1 variable domains and that it is specifically recruited to a subset of B cells. This finding suggests that InvD modulates Ig functions in the intestine and affects direct interactions with a subset of cell surface-exposed B-cell receptors. In summary, our results provide extensive insights into the structure of InvD and its specific interaction with the target molecule in the host.
    • Expansion of functional personalized cells with specific transgene combinations.

      Lipps, Christoph; Klein, Franziska; Wahlicht, Tom; Seiffert, Virginia; Butueva, Milada; Zauers, Jeannette; Truschel, Theresa; Luckner, Martin; Köster, Mario; MacLeod, Roderick; et al. (Springer Nature, 2018-03-08)
      Fundamental research and drug development for personalized medicine necessitates cell cultures from defined genetic backgrounds. However, providing sufficient numbers of authentic cells from individuals poses a challenge. Here, we present a new strategy for rapid cell expansion that overcomes current limitations. Using a small gene library, we expanded primary cells from different tissues, donors, and species. Cell-type-specific regimens that allow the reproducible creation of cell lines were identified. In depth characterization of a series of endothelial and hepatocytic cell lines confirmed phenotypic stability and functionality. Applying this technology enables rapid, efficient, and reliable production of unlimited numbers of personalized cells. As such, these cell systems support mechanistic studies, epidemiological research, and tailored drug development.
    • Regulation of neuroinflammatory properties of glial cells by T cell effector molecules.

      Prajeeth, Chittappen K; Huehn, Jochen; Stangel, Martin; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2018-02)
    • IFN-γ Producing Th1 Cells Induce Different Transcriptional Profiles in Microglia and Astrocytes.

      Prajeeth, Chittappen K; Dittrich-Breiholz, Oliver; Talbot, Steven R; Robert, Philippe A; Huehn, Jochen; Stangel, Martin; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany.; BRICS, Braunschweiger Zentrum für Systembiologie, Rebenring 56,38106 Braunschweig, Germany. (2018-01-01)
      Autoreactive T cells that infiltrate into the central nervous system (CNS) are believed to have a significant role in mediating the pathology of neuroinflammatory diseases like multiple sclerosis. Their interaction with microglia and astrocytes in the CNS is crucial for the regulation of neuroinflammatory processes. Our previous work demonstrated that effectors secreted by Th1 and Th17 cells have different capacities to influence the phenotype and function of glial cells. We have shown that Th1-derived effectors altered the phenotype and function of both microglia and astrocytes whereas Th17-derived effectors induced direct effects only on astrocytes but not on microglia. Here we investigated if effector molecules associated with IFN-γ producing Th1 cells induced different gene expression profiles in microglia and astrocytes. We performed a microarray analysis of RNA isolated from microglia and astrocytes treated with medium and Th-derived culture supernatants and compared the gene expression data. By using the criteria of 2-fold change and a false discovery rate of 0.01 (corrected
    • Filamin A Phosphorylation at Serine 2152 by the Serine/Threonine Kinase Ndr2 Controls TCR-Induced LFA-1 Activation in T Cells.

      Waldt, Natalie; Seifert, Anke; Demiray, Yunus Emre; Devroe, Eric; Turk, Benjamin E; Reichardt, Peter; Mix, Charlie; Reinhold, Annegret; Freund, Christian; Müller, Andreas J; et al. (Frontiers, 2018-01-01)
      The integrin LFA-1 (CD11a/CD18) plays a critical role in the interaction of T cells with antigen presenting cells (APCs) to promote lymphocyte differentiation and proliferation. This integrin can be present either in a closed or in an open active conformation and its activation upon T-cell receptor (TCR) stimulation is a critical step to allow interaction with APCs. In this study we demonstrate that the serine/threonine kinase Ndr2 is critically involved in the initiation of TCR-mediated LFA-1 activation (open conformation) in T cells. Ndr2 itself becomes activated upon TCR stimulation and phosphorylates the intracellular integrin binding partner Filamin A (FLNa) at serine 2152. This phosphorylation promotes the dissociation of FLNa from LFA-1, allowing for a subsequent association of Talin and Kindlin-3 which both stabilize the open conformation of LFA-1. Our data suggest that Ndr2 activation is a crucial step to initiate TCR-mediated LFA-1 activation in T cells.
    • Polymicrobial sepsis and non-specific immunization induce adaptive immunosuppression to a similar degree.

      Schmoeckel, Katrin; Mrochen, Daniel M; Hühn, Jochen; Pötschke, Christian; Bröker, Barbara M; Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2018)
      Sepsis is frequently complicated by a state of profound immunosuppression, in its extreme form known as immunoparalysis. We have studied the role of the adaptive immune system in the murine acute peritonitis model. To read out adaptive immunosuppression, we primed post-septic and control animals by immunization with the model antigen TNP-ovalbumin in alum, and measured the specific antibody-responses via ELISA and ELISpot assay as well as T-cell responses in a proliferation assay after restimulation. Specific antibody titers, antibody affinity and plasma cell counts in the bone marrow were reduced in post-septic animals. The antigen-induced splenic proliferation was also impaired. The adaptive immunosuppression was positively correlated with an overwhelming general antibody response to the septic insult. Remarkably, antigen "overload" by non-specific immunization induced a similar degree of adaptive immunosuppression in the absence of sepsis. In both settings, depletion of regulatory T cells before priming reversed some parameters of the immunosuppression. In conclusion, our data show that adaptive immunosuppression occurs independent of profound systemic inflammation and life-threatening illness.
    • A mathematical model of the impact of insulin secretion dynamics on selective hepatic insulin resistance.

      Zhao, Gang; Wirth, Dagmar; Schmitz, Ingo; Meyer-Hermann, Michael; Braunschweiger Zentrum für Systembiologie, Rebenring 56, 38106, Germany. (2017-11-08)
      Physiological insulin secretion exhibits various temporal patterns, the dysregulation of which is involved in diabetes development. We analyzed the impact of first-phase and pulsatile insulin release on glucose and lipid control with various hepatic insulin signaling networks. The mathematical model suggests that atypical protein kinase C (aPKC) undergoes a bistable switch-on and switch-off, under the control of insulin receptor substrate 2 (IRS2). The activation of IRS1 and IRS2 is temporally separated due to the inhibition of IRS1 by aPKC. The model further shows that the timing of aPKC switch-off is delayed by reduced first-phase insulin and reduced amplitude of insulin pulses. Based on these findings, we propose a sequential model of postprandial hepatic control of glucose and lipid by insulin, according to which delayed aPKC switch-off contributes to selective hepatic insulin resistance, which is a long-standing paradox in the field.
    • Gut memories do not fade: epigenetic regulation of lasting gut homing receptor expression in CD4(+) memory T cells.

      Szilagyi, B A; Triebus, J; Kressler, C; de Almeida, M; Tierling, S; Durek, P; Mardahl, M; Szilagyi, A; Floess, S; Huehn, Jochen; et al. (2017-11)
      The concept of a "topographical memory" in lymphocytes implies a stable expression of homing receptors mediating trafficking of lymphocytes back to the tissue of initial activation. However, a significant plasticity of the gut-homing receptor α4β7 was found in CD8(+) T cells, questioning the concept. We now demonstrate that α4β7 expression in murine CD4(+) memory T cells is, in contrast, imprinted and remains stable in the absence of the inducing factor retinoic acid (RA) or other stimuli from mucosal environments. Repetitive rounds of RA treatment enhanced the stability of de novo induced α4β7. A novel enhancer element in the murine Itga4 locus was identified that showed, correlating to stability, selective DNA demethylation in mucosa-seeking memory cells and methylation-dependent transcriptional activity in a reporter gene assay. This implies that epigenetic mechanisms contribute to the stabilization of α4β7 expression. Analogous DNA methylation patterns could be observed in the human ITGA4 locus, suggesting that its epigenetic regulation is conserved between mice and men. These data prove that mucosa-specific homing mediated by α4β7 is imprinted in CD4(+) memory T cells, reinstating the validity of the concept of "topographical memory" for mucosal tissues, and imply a critical role of epigenetic mechanisms.
    • Effectors of Th1 and Th17 cells act on astrocytes and augment their neuroinflammatory properties.

      Prajeeth, Chittappen K; Kronisch, Julius; Khorooshi, Reza; Knier, Benjamin; Toft-Hansen, Henrik; Gudi, Viktoria; Floess, Stefan; Huehn, Jochen; Owens, Trevor; Korn, Thomas; et al. (2017-10-16)
      Autoreactive Th1 and Th17 cells are believed to mediate the pathology of multiple sclerosis in the central nervous system (CNS). Their interaction with microglia and astrocytes in the CNS is crucial for the regulation of the neuroinflammation. Previously, we have shown that only Th1 but not Th17 effectors activate microglia. However, it is not clear which cells are targets of Th17 effectors in the CNS.
    • Effectors of Th1 and Th17 cells act on astrocytes and augment their neuroinflammatory properties.

      Prajeeth, Chittappen K; Kronisch, Julius; Khorooshi, Reza; Knier, Benjamin; Toft-Hansen, Henrik; Gudi, Viktoria; Floess, Stefan; Huehn, Jochen; Owens, Trevor; Korn, Thomas; et al. (2017-10-16)
      Autoreactive Th1 and Th17 cells are believed to mediate the pathology of multiple sclerosis in the central nervous system (CNS). Their interaction with microglia and astrocytes in the CNS is crucial for the regulation of the neuroinflammation. Previously, we have shown that only Th1 but not Th17 effectors activate microglia. However, it is not clear which cells are targets of Th17 effectors in the CNS. To understand the effects driven by Th17 cells in the CNS, we induced experimental autoimmune encephalomyelitis in wild-type mice and CD4 We observed in α4-deficient mice weak microglial activation but comparable astrogliosis to that of wild-type mice in the regions of the brain populated with Th17 infiltrates, suggesting that Th17 cells target astrocytes and not microglia. In vitro, in response to supernatants from Th1 and Th17 cultures, astrocytes showed altered expression of neurotrophic factors, pro-inflammatory cytokines and chemokines. Furthermore, increased expression of chemokines in Th1- and Th17-treated astrocytes enhanced recruitment of microglia and transendothelial migration of Th17 cells in vitro. Our results demonstrate the delicate interaction between T cell subsets and glial cells and how they communicate to mediate their effects. Effectors of Th1 act on both microglia and astrocytes whereas Th17 effectors preferentially target astrocytes to promote neuroinflammation.
    • Impact of CCR7 on T-Cell Response and Susceptibility to Yersinia pseudotuberculosis Infection.

      Pezoldt, Joern; Pisano, Fabio; Heine, Wiebke; Pasztoi, Maria; Rosenheinrich, Maik; Nuss, Aaron M; Pils, Marina C; Prinz, Immo; Förster, Reinhold; Huehn, Jochen; et al. (2017-09-15)
      To successfully limit pathogen dissemination, an immunological link between the entry tissue of the pathogen and the underlying secondary lymphoid organs (SLOs) needs to be established to prime adaptive immune responses. Here, the prerequisite of CCR7 to mount host immune responses within SLOs during gastrointestinal Yersinia pseudotuberculosis infection to limit pathogen spread was investigated.
    • Activated protein C protects from GvHD via PAR2/PAR3 signalling in regulatory T-cells.

      Ranjan, Satish; Goihl, Alexander; Kohli, Shrey; Gadi, Ihsan; Pierau, Mandy; Shahzad, Khurrum; Gupta, Dheerendra; Bock, Fabian; Wang, Hongjie; Shaikh, Haroon; et al. (2017-08-21)
      Graft-vs.-host disease (GvHD) is a major complication of allogenic hematopoietic stem-cell(HSC) transplantation. GvHD is associated with loss of endothelial thrombomodulin, but the relevance of this for the adaptive immune response to transplanted HSCs remains unknown. Here we show that the protease-activated protein C (aPC), which is generated by thrombomodulin, ameliorates GvHD aPC restricts allogenic T-cell activation via the protease activated receptor (PAR)2/PAR3 heterodimer on regulatory T-cells (Tregs, CD4(+)FOXP3(+)). Preincubation of pan T-cells with aPC prior to transplantation increases the frequency of Tregs and protects from GvHD. Preincubation of human T-cells (HLA-DR4(-)CD4(+)) with aPC prior to transplantation into humanized (NSG-AB°DR4) mice ameliorates graft-vs.-host disease. The protective effect of aPC on GvHD does not compromise the graft vs. leukaemia effect in two independent tumor cell models. Ex vivo preincubation of T-cells with aPC, aPC-based therapies, or targeting PAR2/PAR3 on T-cells may provide a safe and effective approach to mitigate GvHD.Graft-vs.-host disease is a complication of allogenic hematopoietic stem cell transplantation, and is associated with endothelial dysfunction. Here the authors show that activated protein C signals via PAR2/PAR3 to expand Treg cells, mitigating the disease in mice.
    • Mesenteric lymph node stromal cell-derived extracellular vesicles contribute to peripheral de novo induction of Foxp3(+) regulatory T cells.

      Pasztoi, Maria; Pezoldt, Joern; Beckstette, Michael; Lipps, Christoph; Wirth, Dagmar; Rohde, M; Paloczi, Krisztina; Buzas, Edit Iren; Huehn, Jochen; Helmholtz Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-08-18)
      Intestinal regulatory T cells (Tregs) are fundamental in peripheral tolerance toward commensals and food-borne antigens. Accordingly, gut-draining mesenteric lymph nodes (mLNs) represent a site of efficient peripheral de novo Treg induction when compared to skin-draining peripheral LNs (pLNs), and we had recently shown that LN stromal cells substantially contribute to this process. Here, we aimed to unravel the underlying molecular mechanisms and generated immortalized fibroblastic reticular cell lines (iFRCs) from mLNs and pLNs, allowing unlimited investigation of this rare stromal cell subset. In line with our previous findings, mLN-iFRCs showed a higher Treg-inducing capacity when compared to pLN-iFRCs. RNA-seq analysis focusing on secreted molecules revealed a more tolerogenic phenotype of mLN- as compared to pLN-iFRCs. Remarkably, mLN-iFRCs produced substantial numbers of microvesicles (MVs) that carried elevated levels of TGF-β when compared to pLN-iFRC-derived MVs, and these novel players of intercellular communication were shown to be responsible for the tolerogenic properties of mLN-iFRCs. Thus, stromal cells originating from mLNs contribute to peripheral tolerance by fostering de novo Treg induction using TGF-β-carrying MVs. This finding provides novel insights into the subcellular/molecular mechanisms of de novo Treg induction and might serve as promising tool for future therapeutic applications to treat inflammatory disorders.
    • TCR signalling network organization at the immunological synapses of murine regulatory T cells.

      van Ham, Marco; Teich, René; Philipsen, Lars; Niemz, Jana; Amsberg, Nicole; Wissing, Josef; Nimtz, Manfred; Gröbe, Lothar; Kliche, Stefanie; Thiel, Nadine; et al. (2017-08-17)
      Regulatory T (Treg) cells require T-cell receptor (TCR) signalling to exert their immunosuppressive activity, but the precise organization of the TCR signalling network compared to conventional T (Tconv) cells remains elusive. By using accurate mass spectrometry and multi-epitope ligand cartography (MELC) we characterized TCR signalling and recruitment of TCR signalling components to the immunological synapse (IS) in Treg cells and Tconv cells. With the exception of Themis which we detected in lower amounts in Treg cells, other major TCR signalling components were found equally abundant, however, their phosphorylation-status notably discriminates Treg cells from Tconv cells. Overall, this study identified 121 Treg cell-specific phosphorylations. Short-term triggering of T cell subsets via CD3 and CD28 widely harmonized these variations with the exception of eleven TCR signalling components that mainly regulate cytoskeleton dynamics and molecular transport. Accordingly, conjugation with B cells indeed caused variant cellular morphology and revealed a Treg cell-specific recruitment of TCR signalling components such as PKCθ, PLCγ1 and ZAP70 as well as B cell-derived CD86 into the IS. Together, results from this study support the existence of a Treg cell-specific IS and suggest Treg cell-specific cytoskeleton dynamics as a novel determinant for the unique functional properties of Treg cells.
    • Helicobacter pylori and its secreted immunomodulator VacA protect against anaphylaxis in experimental models of food allergy.

      Kyburz, Andreas; Urban, Sabine; Altobelli, Aleksandra; Floess, Stefan; Huehn, Jochen; Cover, Timothy L; Müller, Anne; Helmholtz Centre for infection research GmbH, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2017-08-12)
      Food allergy is an increasingly common health problem in Western populations. Epidemiological studies have suggested both positive and negative associations between food allergy and infection with the gastric bacterium Helicobacter pylori.
    • Unique properties of thymic antigen-presenting cells promote epigenetic imprinting of alloantigen-specific regulatory T cells.

      Garg, Garima; Nikolouli, Eirini; Hardtke-Wolenski, Matthias; Toker, Aras; Ohkura, Naganari; Beckstette, Michael; Miyao, Takahisa; Geffers, Robert; Floess, Stefan; Gerdes, Norbert; et al. (2017-05-30)
      Regulatory T cells (Tregs) are potential immunotherapeutic candidates to induce transplantation tolerance. However, stability of Tregs still remains contentious and may potentially restrict their clinical use. Recent work suggested that epigenetic imprinting of Foxp3 and other Treg-specific signature genes is crucial for stabilization of immunosuppressive properties of Foxp3+ Tregs, and that these events are initiated already during early stages of thymic Treg development. However, the mechanisms governing this process remain largely unknown. Here we demonstrate that thymic antigen-presenting cells (APCs), including thymic dendritic cells (t-DCs) and medullary thymic epithelial cells (mTECs), can induce a more pronounced demethylation of Foxp3 and other Treg-specific epigenetic signature genes in developing Tregs when compared to splenic DCs (sp-DCs). Transcriptomic profiling of APCs revealed differential expression of secreted factors and costimulatory molecules, however neither addition of conditioned media nor interference with costimulatory signals affected Foxp3 induction by thymic APCs in vitro. Importantly, when tested in vivo both mTEC- and t-DC-generated alloantigen-specific Tregs displayed significantly higher efficacy in prolonging skin allograft acceptance when compared to Tregs generated by sp-DCs. Our results draw attention to unique properties of thymic APCs in initiating commitment towards stable and functional Tregs, a finding that could be highly beneficial in clinical immunotherapy.
    • IRAP+ endosomes restrict TLR9 activation and signaling.

      Babdor, Joel; Descamps, Delphyne; Adiko, Aimé Cézaire; Tohmé, Mira; Maschalidi, Sophia; Evnouchidou, Irini; Vasconcellos, Luiz Ricardo; De Luca, Mariacristina; Mauvais, Francois-Xavier; Garfa-Traore, Meriem; et al. (2017-05)
      The retention of intracellular Toll-like receptors (TLRs) in the endoplasmic reticulum prevents their activation under basal conditions. TLR9 is activated by sensing ligands in specific endosomal-lysosomal compartments. Here we identified IRAP+ endosomes as major cellular compartments for the early steps of TLR9 activation in dendritic cells (DCs). Both TLR9 and its ligand, the dinucleotide CpG, were present as cargo in IRAP+ endosomes. In the absence of the aminopeptidase IRAP, the trafficking of CpG and TLR9 to lysosomes and signaling via TLR9 were enhanced in DCs and in mice following bacterial infection. IRAP stabilized CpG-containing endosomes by interacting with the actin-nucleation factor FHOD4, which slowed the trafficking of TLR9 toward lysosomes. Thus, endosomal retention of TLR9 via the interaction of IRAP with the actin cytoskeleton is a mechanism that prevents hyper-activation of TLR9 in DCs.
    • Yersinia pseudotuberculosis supports Th17 differentiation and limits de novo regulatory T cell induction by directly interfering with T cell receptor signaling.

      Pasztoi, Maria; Bonifacius, Agnes; Pezoldt, Joern; Kulkarni, Devesha; Niemz, Jana; Yang, Juhao; Teich, René; Hajek, Janina; Pisano, Fabio; Rohde, Manfred; et al. (2017-04-04)
      Adaptive immunity critically contributes to control acute infection with enteropathogenic Yersinia pseudotuberculosis; however, the role of CD4(+) T cell subsets in establishing infection and allowing pathogen persistence remains elusive. Here, we assessed the modulatory capacity of Y. pseudotuberculosis on CD4(+) T cell differentiation. Using in vivo assays, we report that infection with Y. pseudotuberculosis resulted in enhanced priming of IL-17-producing T cells (Th17 cells), whereas induction of Foxp3(+) regulatory T cells (Tregs) was severely disrupted in gut-draining mesenteric lymph nodes (mLNs), in line with altered frequencies of tolerogenic and proinflammatory dendritic cell (DC) subsets within mLNs. Additionally, by using a DC-free in vitro system, we could demonstrate that Y. pseudotuberculosis can directly modulate T cell receptor (TCR) downstream signaling within naïve CD4(+) T cells and Tregs via injection of effector molecules through the type III secretion system, thereby affecting their functional properties. Importantly, modulation of naïve CD4(+) T cells by Y. pseudotuberculosis resulted in an enhanced Th17 differentiation and decreased induction of Foxp3(+) Tregs in vitro. These findings shed light to the adjustment of the Th17-Treg axis in response to acute Y. pseudotuberculosis infection and highlight the direct modulation of CD4(+) T cell subsets by altering their TCR downstream signaling.