• Limited role of regulatory T cells during acute Theiler virus-induced encephalitis in resistant C57BL/6 mice

      Prajeeth, Chittappen K; Beineke, Andreas; Iskandar, Cut D; Gudi, Viktoria; Herder, Vanessa; Gerhauser, Ingo; Haist, Verena; Teich, René; Huehn, Jochen; Baumgärtner, Wolfgang; Stangel, Martin (2014-11-13)
      Abstract Background Theiler’s murine encephalomyelitis virus (TMEV) infection represents a commonly used infectious animal model to study various aspects of the pathogenesis of multiple sclerosis (MS). In susceptible SJL mice, dominant activity of Foxp3+ CD4+ regulatory T cells (Tregs) in the CNS partly contributes to viral persistence and progressive demyelination. On the other hand, resistant C57BL/6 mice rapidly clear the virus by mounting a strong antiviral immune response. However, very little is known about the role of Tregs in regulating antiviral responses during acute encephalitis in resistant mouse strains. Methods In this study, we used DEREG mice that express the diphtheria toxin (DT) receptor under control of the foxp3 locus to selectively deplete Foxp3+ Tregs by injection of DT prior to infection and studied the effect of Treg depletion on the course of acute Theiler’s murine encephalomyelitis (TME). Results As expected, DEREG mice that are on a C57BL/6 background were resistant to TMEV infection and cleared the virus within days of infection, regardless of the presence or absence of Tregs. Nevertheless, in the absence of Tregs we observed priming of stronger effector T cell responses in the periphery, which subsequently resulted in a transient increase in the frequency of IFNγ-producing T cells in the brain at an early stage of infection. Histological and flow cytometric analysis revealed that this transiently increased frequency of brain-infiltrating IFNγ-producing T cells in Treg-depleted mice neither led to an augmented antiviral response nor enhanced inflammation-mediated tissue damage. Intriguingly, Treg depletion did not change the expression of IL-10 in the infected brain, which might play a role for dampening the inflammatory damage caused by the increased number of effector T cells. Conclusion We therefore propose that unlike susceptible mice strains, interfering with the Treg compartment of resistant mice only has negligible effects on virus-induced pathologies in the CNS. Furthermore, in the absence of Tregs, local anti-inflammatory mechanisms might limit the extent of damage caused by strong anti-viral response in the CNS.
    • Viral Infection of the Central Nervous System Exacerbates Interleukin-10 Receptor Deficiency-Mediated Colitis in SJL Mice.

      Uhde, Ann-Kathrin; Herder, Vanessa; Akram Khan, Muhammad; Ciurkiewicz, Malgorzata; Schaudien, Dirk; Teich, René; Floess, Stefan; Baumgärtner, Wolfgang; Huehn, Jochen; Beineke, Andreas; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016)
      Theiler´s murine encephalomyelitis virus (TMEV)-infection is a widely used animal model for studying demyelinating disorders, including multiple sclerosis (MS). The immunosuppressive cytokine Interleukin (IL)-10 counteracts hyperactive immune responses and critically controls immune homeostasis in infectious and autoimmune disorders. In order to investigate the effect of signaling via Interleukin-10 receptor (IL-10R) in infectious neurological diseases, TMEV-infected SJL mice were treated with IL-10R blocking antibody (Ab) in the acute and chronic phase of the disease. The findings demonstrate that (i) Ab-mediated IL-10 neutralization leads to progressive colitis with a reduction in Foxp3+ regulatory T cells and increased numbers of CD8+CD44+ memory T cells as well as activated CD4+CD69+ and CD8+CD69+ T cells in uninfected mice. (ii) Concurrent acute TMEV-infection worsened enteric disease-mediated by IL-10R neutralization. Virus-triggered effects were associated with an enhanced activation of CD4+ T helper cells and CD8+ cytotoxic T lymphocytes and augmented cytokine expression. By contrast, (iii) IL-10R neutralization during chronic TMEV-infection was not associated with enhanced peripheral immunopathology but an increased CD3+ T cell influx in the spinal cord. IL-10R neutralization causes a breakdown in peripheral immune tolerance in genetically predisposed mice, which leads to immune-mediated colitis, resembling inflammatory bowel disease. Hyperactive immune state following IL-10R blockade is enhanced by central nervous system-restricted viral infection in a disease phase-dependent manner.
    • Inhibition of the JAK/STAT Signaling Pathway in Regulatory T Cells Reveals a Very Dynamic Regulation of Foxp3 Expression.

      Goldstein, Jérémie D; Burlion, Aude; Zaragoza, Bruno; Sendeyo, Kélhia; Polansky, Julia K; Huehn, Jochen; Piaggio, Eliane; Salomon, Benoit L; Marodon, Gilles; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2016)
      The IL-2/JAK3/STAT-5 signaling pathway is involved on the initiation and maintenance of the transcription factor Foxp3 in regulatory T cells (Treg) and has been associated with demethylation of the intronic Conserved Non Coding Sequence-2 (CNS2). However, the role of the JAK/STAT pathway in controlling Foxp3 in the short term has been poorly investigated. Using two different JAK/STAT pharmacological inhibitors, we observed a detectable loss of Foxp3 after 10 min. of treatment that affected 70% of the cells after one hour. Using cycloheximide, a general inhibitor of mRNA translation, we determined that Foxp3, but not CD25, has a high turnover in IL-2 stimulated Treg. This reduction was correlated with a rapid reduction of Foxp3 mRNA. This loss of Foxp3 was associated with a loss in STAT-5 binding to the CNS2, which however remains demethylated. Consequently, Foxp3 expression returns to normal level upon restoration of basal JAK/STAT signaling in vivo. Reduced expression of several genes defining Treg identity was also observed upon treatment. Thus, our results demonstrate that Foxp3 has a rapid turn over in Treg partly controlled at the transcriptional level by the JAK/STAT pathway.
    • Foxp3(+) T cells expressing RORγt represent a stable regulatory T-cell effector lineage with enhanced suppressive capacity during intestinal inflammation.

      Yang, B-H; Hagemann, S; Mamareli, P; Lauer, U; Hoffmann, U; Beckstette, M; Föhse, L; Prinz, I; Pezoldt, J; Suerbaum, S; Sparwasser, Tim; Hamann, A; Floess, S; Huehn, J; Lochner, M; Helmholtz Centre for infection research, Inhoffenstr.7, 38124 Braunschweig, Germany. (2016-03)
      Foxp3 (forkhead box P3 transcription factor)-expressing regulatory T cells (Tregs) are essential for immunological tolerance, best illustrated by uncontrolled effector T-cell responses and autoimmunity upon loss of Foxp3 expression. Tregs can adopt specific effector phenotypes upon activation, reflecting the diversity of functional demands in the different tissues of the body. Here, we report that Foxp3(+)CD4(+) T cells coexpressing retinoic acid-related orphan receptor-γt (RORγt), the master transcription factor for T helper type 17 (Th17) cells, represent a stable effector Treg lineage. Transcriptomic and epigenetic profiling revealed that Foxp3(+)RORγt(+) T cells display signatures of both Tregs and Th17 cells, although the degree of similarity was higher to Foxp3(+)RORγt(-) Tregs than to Foxp3(-)RORγt(+) T cells. Importantly, Foxp3(+)RORγt(+) T cells were significantly demethylated at Treg-specific epigenetic signature genes such as Foxp3, Ctla-4, Gitr, Eos, and Helios, suggesting that these cells have a stable regulatory rather than inflammatory function. Indeed, adoptive transfer of Foxp3(+)RORγt(+) T cells in the T-cell transfer colitis model confirmed their Treg function and lineage stability in vivo, and revealed an enhanced suppressive capacity as compared with Foxp3(+)RORγt(-) Tregs. Thus, our data suggest that RORγt expression in Tregs contributes to an optimal suppressive capacity during gut-specific immune responses, rendering Foxp3(+)RORγt(+) T cells as an important effector Treg subset in the intestinal system.
    • Promiscuous Foxp3-cre activity reveals a differential requirement for CD28 in Foxp3⁺ and Foxp3⁻ T cells.

      Franckaert, Dean; Dooley, James; Roos, Evelyne; Floess, Stefan; Huehn, Jochen; Luche, Herve; Fehling, Hans Joerg; Liston, Adrian; Linterman, Michelle A; Schlenner, Susan M; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2015-04)
      Costimulatory signals by CD28 are critical for thymic regulatory T-cell (Treg) development. To determine the functional relevance of CD28 for peripheral Treg post thymic selection, we crossed the widely used Forkhead box protein 3 (Foxp3)-CreYFP mice to mice bearing a conditional Cd28 allele. Treg-specific CD28 deficiency provoked a severe autoimmune syndrome as a result of a strong disadvantage in competitive fitness and proliferation of CD28-deficient Tregs. By contrast, Treg survival and lineage integrity were not affected by the lack of CD28. This data demonstrate that, even after the initial induction requirement, Treg maintain a higher dependency on CD28 signalling than conventional T cells for homeostasis. In addition, we found the Foxp3-CreYFP allele to be a hypomorph, with reduced Foxp3 protein levels. Furthermore, we report here the stochastic activity of the Foxp3-CreYFP allele in non-Tregs, sufficient to recombine some conditional alleles (including Cd28) but not others (including R26-RFP). This hypomorphism and 'leaky' expression of the Foxp3-CreYFP allele should be considered when analysing the conditionally mutated Treg.
    • Limited role of regulatory T cells during acute Theiler virus-induced encephalitis in resistant C57BL/6 mice.

      Prajeeth, Chittappen K; Beineke, Andreas; Iskandar, Cut Dahlia; Gudi, Viktoria; Herder, Vanessa; Gerhauser, Ingo; Haist, Verena; Teich, René; Huehn, Jochen; Baumgärtner, Wolfgang; Stangel, Martin; Helmholtz Centre for infection research, Inhoffenstr. 7, D-38124 Braunschweig, Germany. (2014)
      Theiler's murine encephalomyelitis virus (TMEV) infection represents a commonly used infectious animal model to study various aspects of the pathogenesis of multiple sclerosis (MS). In susceptible SJL mice, dominant activity of Foxp3(+) CD4(+) regulatory T cells (Tregs) in the CNS partly contributes to viral persistence and progressive demyelination. On the other hand, resistant C57BL/6 mice rapidly clear the virus by mounting a strong antiviral immune response. However, very little is known about the role of Tregs in regulating antiviral responses during acute encephalitis in resistant mouse strains.
    • Development of a unique epigenetic signature during in vivo Th17 differentiation.

      Yang, Bi-Huei; Floess, Stefan; Hagemann, Stefanie; Deyneko, Igor V; Groebe, Lothar; Pezoldt, Joern; Sparwasser, Tim; Lochner, Matthias; Huehn, Jochen; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2015-02-18)
      Activated naive CD4(+) T cells are highly plastic cells that can differentiate into various T helper (Th) cell fates characterized by the expression of effector cytokines like IFN-γ (Th1), IL-4 (Th2) or IL-17A (Th17). Although previous studies have demonstrated that epigenetic mechanisms including DNA demethylation can stabilize effector cytokine expression, a comprehensive analysis of the changes in the DNA methylation pattern during differentiation of naive T cells into Th cell subsets is lacking. Hence, we here performed a genome-wide methylome analysis of ex vivo isolated naive CD4(+) T cells, Th1 and Th17 cells. We could demonstrate that naive CD4(+) T cells share more demethylated regions with Th17 cells when compared to Th1 cells, and that overall Th17 cells display the highest number of demethylated regions, findings which are in line with the previously reported plasticity of Th17 cells. We could identify seven regions located in Il17a, Zfp362, Ccr6, Acsbg1, Dpp4, Rora and Dclk1 showing pronounced demethylation selectively in ex vivo isolated Th17 cells when compared to other ex vivo isolated Th cell subsets and in vitro generated Th17 cells, suggesting that this unique epigenetic signature allows identifying and functionally characterizing in vivo generated Th17 cells.
    • CD8+ Foxp3+ T cells share developmental and phenotypic features with classical CD4+ Foxp3+ regulatory T cells but lack potent suppressive activity.

      Mayer, Christian T; Floess, Stefan; Baru, Abdul Mannan; Lahl, Katharina; Huehn, Jochen; Sparwasser, Tim (2011-03)
      "Suppressor T cells" were historically defined within the CD8(+) T-cell compartment and recent studies have highlighted several naturally occurring CD8(+) Foxp3(-) Treg populations. However, the relevance of CD8(+) Foxp3(+) T cells, which represent a minor population in both thymi and secondary lymphoid organs of nonmanipulated mice, remains unclear. We here demonstrate that de novo Foxp3 induction in peripheral CD8(+) Foxp3(-) T cells is counter-regulated by DC-mediated co-stimulation via CD80/CD86. CD8(+) Foxp3(+) T cells fail to develop in TCR-transgenic mice with Rag1(-/-) background, similar to classical CD4(+) Foxp3(+) Tregs. Notably, both naturally occurring and induced CD8(+) Foxp3(+) T cells express bona fide Treg markers including CD25, GITR, CTLA4 and CD103, and show defective IFN-γ production upon restimulation when compared with their CD8(+) Foxp3(-) counterparts. However, utilizing DEREG transgenic mice for the isolation of Foxp3(+) cells by eGFP reporter expression, we demonstrate that induced CD8(+) Foxp3(+) T cells similar to activated CD8(+) Foxp3(-) T cells only mildly suppress T-cell proliferation and IFN-γ production. We therefore categorize CD8(+) Foxp3(+) T cells as a tightly controlled population sharing certain developmental and phenotypic properties with classical CD4(+) Foxp3(+) Tregs, but lacking potent suppressive activity.
    • The Treg-specific demethylated region stabilizes Foxp3 expression independently of NF-κB signaling.

      Schreiber, Lisa; Pietzsch, Beate; Floess, Stefan; Farah, Carla; Jänsch, Lothar; Schmitz, Ingo; Huehn, Jochen; Department Experimental Immunology, Helmholtz Centre for Infection Research, Braunschweig, Germany. (2014)
      Regulatory T cells (Tregs) obtain immunosuppressive capacity by the upregulation of forkhead box protein 3 (Foxp3), and persistent expression of this transcription factor is required to maintain their immune regulatory function and ensure immune homeostasis. Stable Foxp3 expression is achieved through epigenetic modification of the Treg-specific demethylated region (TSDR), an evolutionarily conserved non-coding element within the Foxp3 gene locus. Here, we present molecular data suggesting that TSDR enhancer activity is restricted to T cells and cannot be induced in other immune cells such as macrophages or B cells. Since NF-κB signaling has been reported to be instrumental to induce Foxp3 expression during Treg development, we analyzed how NF-κB factors are involved in the molecular regulation of the TSDR. Unexpectedly, we neither observed transcriptional activity of a previously postulated NF-κB binding site within the TSDR nor did the entire TSDR show any transcriptional responsiveness to NF-κB activation at all. Finally, the NF-κB subunit c-Rel revealed to be dispensable for epigenetic imprinting of sustained Foxp3 expression by TSDR demethylation. In conclusion, we show that NF-κB signaling is not substantially involved in TSDR-mediated stabilization of Foxp3 expression in Tregs.
    • Epigenetic modification of the human CCR6 gene is associated with stable CCR6 expression in T cells.

      Steinfelder, Svenja; Floess, Stefan; Engelbert, Dirk; Haeringer, Barbara; Baron, Udo; Rivino, Laura; Steckel, Bodo; Gruetzkau, Andreas; Olek, Sven; Geginat, Jens; Huehn, Jochen; Hamann, Alf; Dept. of experimental immunology, Helmholtz Centre for infection reseach, Inhoffenstr. 7, D38124 Braunschweig, Germany. (2011-03-10)
      CCR6 is a chemokine receptor expressed on Th17 cells and regulatory T cells that is induced by T-cell priming with certain cytokines, but how its expression and stability are regulated at the molecular level is largely unknown. Here, we identified and characterized a noncoding region of the human CCR6 locus that displayed unmethylated CpG motifs (differentially methylated region [DMR]) selectively in CCR6(+) lymphocytes. CCR6 expression on circulating CD4(+) T cells was stable on cytokine-induced proliferation but partially down-regulated on T-cell receptor stimulation. However, CCR6 down-regulation was mostly transient, and the DMR within the CCR6 locus remained demethylated. Notably, in vitro induction of CCR6 expression with cytokines in T-cell receptor-activated naive CD4(+) T cells was not associated with a demethylated DMR and resulted in unstable CCR6 expression. Conversely, treatment with the DNA methylation inhibitor 5'-azacytidine induced demethylation of the DMR and led to increased and stable CCR6 expression. Finally, when cloned into a reporter gene plasmid, the DMR displayed transcriptional activity in memory T cells that was suppressed by DNA methylation. In summary, we have identified a noncoding region of the human CCR6 gene with methylation-sensitive transcriptional activity in CCR6(+) T cells that controls stable CCR6 expression via epigenetic mechanisms.
    • Neuropilin 1 is expressed on thymus-derived natural regulatory T cells, but not mucosa-generated induced Foxp3+ T reg cells.

      Weiss, Jonathan M; Bilate, Angelina M; Gobert, Michael; Ding, Yi; Curotto de Lafaille, Maria A; Parkhurst, Christopher N; Xiong, Huizhong; Dolpady, Jayashree; Frey, Alan B; Ruocco, Maria Grazia; Yang, Yi; Floess, Stefan; Huehn, Jochen; Oh, Soyoung; Li, Ming O; Niec, Rachel E; Rudensky, Alexander Y; Dustin, Michael L; Littman, Dan R; Lafaille, Juan J (2012-09-24)
      Foxp3 activity is essential for the normal function of the immune system. Two types of regulatory T (T reg) cells express Foxp3, thymus-generated natural T reg (nT reg) cells, and peripherally generated adaptive T reg (iT reg) cells. These cell types have complementary functions. Until now, it has not been possible to distinguish iT reg from nT reg cells in vivo based solely on surface markers. We report here that Neuropilin 1 (Nrp1) is expressed at high levels by most nT reg cells; in contrast, mucosa-generated iT reg and other noninflammatory iT reg cells express low levels of Nrp1. We found that Nrp1 expression is under the control of TGF-β. By tracing nT reg and iT reg cells, we could establish that some tumors have a very large proportion of infiltrating iT reg cells. iT reg cells obtained from highly inflammatory environments, such as the spinal cords of mice with spontaneous autoimmune encephalomyelitis (EAE) and the lungs of mice with chronic asthma, express Nrp1. In the same animals, iT reg cells in secondary lymphoid organs remain Nrp1(low). We also determined that, in spontaneous EAE, iT reg cells help to establish a chronic phase of the disease.
    • Effector molecules released by Th1 but not Th17 cells drive an M1 response in microglia.

      Prajeeth, Chittappen K; Löhr, Kirsten; Floess, Stefan; Zimmermann, Julian; Ulrich, Reiner; Gudi, Viktoria; Beineke, Andreas; Baumgärtner, Wolfgang; Müller, Marcus; Huehn, Jochen; Stangel, Martin (2014-03)
      Microglia act as sensors of inflammation in the central nervous system (CNS) and respond to many stimuli. Other key players in neuroinflammatory diseases are CD4+ T helper cell (Th) subsets that characteristically secrete IFN-γ (Th1) or IL-17 (Th17). However, the potential of a distinct cytokine milieu generated by these effector T cell subsets to modulate microglial phenotype and function is poorly understood. We therefore investigated the ability of factors secreted by Th1 and Th17 cells to induce microglial activation. In vitro experiments wherein microglia were cultured in the presence of supernatants derived from polarized Th1 or Th17 cultures, revealed that Th1-associated factors could directly activate and trigger a proinflammatory M1-type gene expression profile in microglia that was cell-cell contact independent, whereas Th17 cells or its associated factors did not have any direct influence on microglia. To assess the effects of the key Th17 effector cytokine IL-17A in vivo we used transgenic mice in which IL-17A is specifically expressed in astrocytes. Flow cytometric and histological analysis revealed only subtle changes in the phenotype of microglia suggesting only minimal effects of constitutively produced IL-17A on microglia in vivo. Neither IL-23 signaling nor addition of GM-CSF, a recently described effector molecule of Th17 cells, changed the incapacity of Th17 cells to activate microglia. These findings demonstrate a potent effect of Th1 cells on microglia, however, the mechanism of how Th17 cells achieve their effect in CNS inflammation remains unclear.
    • Neuroprotective intervention by interferon-γ blockade prevents CD8+ T cell-mediated dendrite and synapse loss.

      Kreutzfeldt, Mario; Bergthaler, Andreas; Fernandez, Marylise; Brück, Wolfgang; Steinbach, Karin; Vorm, Mariann; Coras, Roland; Blümcke, Ingmar; Bonilla, Weldy V; Fleige, Anne; Forman, Ruth; Müller, Werner; Becher, Burkhard; Misgeld, Thomas; Kerschensteiner, Martin; Pinschewer, Daniel D; Merkler, Doron; Department of Pathology and Immunology and 2 World Health Organization Collaborating Centre for Vaccine Immunology, University of Geneva, 1211 Geneva, Switzerland. (2013-09-23)
      Neurons are postmitotic and thus irreplaceable cells of the central nervous system (CNS). Accordingly, CNS inflammation with resulting neuronal damage can have devastating consequences. We investigated molecular mediators and structural consequences of CD8(+) T lymphocyte (CTL) attack on neurons in vivo. In a viral encephalitis model in mice, disease depended on CTL-derived interferon-γ (IFN-γ) and neuronal IFN-γ signaling. Downstream STAT1 phosphorylation and nuclear translocation in neurons were associated with dendrite and synapse loss (deafferentation). Analogous molecular and structural alterations were also found in human Rasmussen encephalitis, a CTL-mediated human autoimmune disorder of the CNS. Importantly, therapeutic intervention by IFN-γ blocking antibody prevented neuronal deafferentation and clinical disease without reducing CTL responses or CNS infiltration. These findings identify neuronal IFN-γ signaling as a novel target for neuroprotective interventions in CTL-mediated CNS disease.
    • TGF-β Signalling Is Required for CD4(+) T Cell Homeostasis But Dispensable for Regulatory T Cell Function.

      Sledzińska, Anna; Hemmers, Saskia; Mair, Florian; Gorka, Oliver; Ruland, Jürgen; Fairbairn, Lynsey; Nissler, Anja; Müller, Werner; Waisman, Ari; Becher, Burkhard; Buch, Thorsten; Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland. (2013-10)
      TGF-β is widely held to be critical for the maintenance and function of regulatory T (Treg) cells and thus peripheral tolerance. This is highlighted by constitutive ablation of TGF-β receptor (TR) during thymic development in mice, which leads to a lethal autoimmune syndrome. Here we describe that TGF-β-driven peripheral tolerance is not regulated by TGF-β signalling on mature CD4(+) T cells. Inducible TR2 ablation specifically on CD4(+) T cells did not result in a lethal autoinflammation. Transfer of these TR2-deficient CD4(+) T cells to lymphopenic recipients resulted in colitis, but not overt autoimmunity. In contrast, thymic ablation of TR2 in combination with lymphopenia led to lethal multi-organ inflammation. Interestingly, deletion of TR2 on mature CD4(+) T cells does not result in the collapse of the Treg cell population as observed in constitutive models. Instead, a pronounced enlargement of both regulatory and effector memory T cell pools was observed. This expansion is cell-intrinsic and seems to be caused by increased T cell receptor sensitivity independently of common gamma chain-dependent cytokine signals. The expression of Foxp3 and other regulatory T cells markers was not dependent on TGF-β signalling and the TR2-deficient Treg cells retained their suppressive function both in vitro and in vivo. In summary, absence of TGF-β signalling on mature CD4(+) T cells is not responsible for breakdown of peripheral tolerance, but rather controls homeostasis of mature T cells in adult mice.
    • Extracellular NAD+ shapes the Foxp3+ regulatory T cell compartment through the ART2-P2X7 pathway.

      Hubert, Sandra; Rissiek, Björn; Klages, Katjana; Huehn, Jochen; Sparwasser, Tim; Haag, Friedrich; Koch-Nolte, Friedrich; Boyer, Olivier; Seman, Michel; Adriouch, Sahil; Institut National de la Santé et de la Recherche Medicale, U905, 76183 Rouen, France. (2010-11-22)
      CD4(+)CD25(+)FoxP3(+) regulatory T cells (T reg cells) play a major role in the control of immune responses but the factors controlling their homeostasis and function remain poorly characterized. Nicotinamide adenine dinucleotide (NAD(+)) released during cell damage or inflammation results in ART2.2-mediated ADP-ribosylation of the cytolytic P2X7 receptor on T cells. We show that T reg cells express the ART2.2 enzyme and high levels of P2X7 and that T reg cells can be depleted by intravenous injection of NAD(+). Moreover, lower T reg cell numbers are found in mice deficient for the NAD-hydrolase CD38 than in wild-type, P2X7-deficient, or ART2-deficient mice, indicating a role for extracellular NAD(+) in T reg cell homeostasis. Even routine cell preparation leads to release of NAD(+) in sufficient quantities to profoundly affect T reg cell viability, phenotype, and function. We demonstrate that T reg cells can be protected from the deleterious effects of NAD(+) by an inhibitory ART2.2-specific single domain antibody. Furthermore, selective depletion of T reg cells by systemic administration of NAD(+) can be used to promote an antitumor response in several mouse tumor models. Collectively, our data demonstrate that NAD(+) influences survival, phenotype, and function of T reg cells and provide proof of principle that acting on the ART2-P2X7 pathway represents a new strategy to manipulate T reg cells in vivo.
    • To be or not to be a Treg cell: lineage decisions controlled by epigenetic mechanisms.

      Toker, Aras; Huehn, Jochen; Experimental Immunology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124 Braunschweig, Germany. (2011)
      Regulatory T (T(reg)) cells are a unique CD4(+) T cell lineage that plays a crucial role in the maintenance of immunological tolerance. The Forkhead box transcription factor Foxp3 is critically involved in T(reg) cell development and responsible for determining the suppressive function of these cells. The majority of Foxp3(+) T(reg) cells are generated during T cell development within the thymus and show features of a stable T cell lineage. New work indicates that both induction and stabilization of Foxp3 expression are under epigenetic control, which suggests that selective interference with the underlying chromatin remodeling mechanisms might enable the development of future therapeutic strategies targeting T(reg) cells.