Search

The transcription factor Foxp3/FOXP3 orchestrates regulatory T (Treg) cell development and function by interacting with numerous target genes and partner proteins. Functional analysis of naturally occurring or engineered Foxp3/FOXP3 mutations has provided important insights into how the complex Foxp3/FOXP3-centered molecular network operates. Here, we describe detailed protocols for retroviral transduction of murine primary conventional CD4

Pathogenic T helper cells (Th cells) that respond to self-antigen cannot be easily distinguished from beneficial Th cells. These cells can generate systemic autoimmune disease in response to widely expressed self-antigens. In this study, we have identified neuropilin-1 (NRP1) as a cell surface marker of self-reactive Th cells. NRP1

Regulatory T (Treg) cells that express the lineage-defining transcription factor Foxp3 play a pivotal role in establishing and maintaining immune and tissue homeostasis. Foxp3 serves as a highly connected ‘hub’, interacting with numerous genomic sites and partner proteins, in the molecular network that orchestrates multiple facets of Treg cell differentiation and function. Treg cells are distributed throughout the body from lymphoid tissues to most non-lymphoid tissues, where they exert anti-inflammatory and protective functions appropriate for the tissue and immune environment. They are thus capable of adapting to diverse and changing environments by dynamically integrating extrinsic cues with the intrinsic molecular network. In this review, we discuss recent advances in our understanding of the cell-intrinsic and -extrinsic mechanisms underlying the adaptability of Treg cells and we propose a crucial role for the Foxp3-centered molecular network, which operates in a multimodal and adaptive manner in response to environmental signals.

Background: Even though the mother and the fetus of placental mammals are immunologically non-self with respect to one other, mutual exchange of small numbers of cells between them is known to occur. Maternal cells entering the fetus, called maternal microchimeric cells (MMc cells), are thought to be involved in different physiological phenomena, such as establishing immune tolerance, tissue repair, and the pathogenesis or deterioration of some inflammatory diseases and congenital malformations. While specific MMc cell types have been reported as associated with these phenomena, the contribution of MMc cells to these different outcomes remains unknown. As one possibility, we hypothesized that different embryos have differing repertoires of MMc cell types, leading to or biasing embryos toward different fates. To date, no studies have succeeded in identifying the MMc cell type repertoire of a single embryo. Accordingly, here, we isolated MMc cells from whole mouse embryos, determined their types, and analyzed their MMc cell type variability.Results: By combining our previously established, whole-embryonic MMc isolation method with single-cell RNA sequencing, we successfully estimated the cell type repertoires of MMc cells isolated from 26 mouse embryos. The majority of MMc cells were immune-related cells, such as myeloid cell and granulocyte. We also detected stem cell-like MMc cells expressing proliferation marker genes and terminally differentiated cells. As hypothesized, we noted statistically significant inter-individual variation in the proportion of immune-related cells in the different embryos.Conclusions: We here successfully estimated MMc cell types in individual whole mouse embryos. The proportion of immune-related cells significantly differed among the individual embryos, suggesting this as one of the potential mechanisms underlying the differing MMc-related physiological phenomena in offspring. These findings provide insight into cell-level epigenetics by maternal cells.

Antigen-specific peripheral tolerance is crucial to prevent the development of organ-specific autoimmunity. However, its function decoupled from thymic tolerance remains unclear. We used desmoglein 3 (Dsg3), a pemphigus antigen expressed in keratinocytes, to analyze peripheral tolerance under physiological antigen-expression conditions. Dsg3-deficient thymi were transplanted into athymic mice to create a unique condition in which Dsg3 was expressed only in peripheral tissue but not in the thymus. When bone marrow transfer was conducted from high-avidity Dsg3-specific T cell receptor–transgenic mice to thymus-transplanted mice, Dsg3-specific CD4(+) T cells developed in the transplanted thymus but subsequently disappeared in the periphery. Additionally, when Dsg3-specific T cells developed in Dsg3(−/−) mice were adoptively transferred into Dsg3-sufficient recipients, the T cells disappeared in an antigen-specific manner without inducing autoimmune dermatitis. However, Dsg3-specific T cells overcame this disappearance and thus induced autoimmune dermatitis in Treg-ablated recipients but not in Foxp3-mutant recipients with dysfunctional Tregs. The molecules involved in disappearance were sought by screening the transcriptomes of wild-type and Foxp3-mutant Tregs. OX40 of Tregs was suggested to be responsible. Consistently, when OX40 expression of Tregs was constrained, Dsg3-specific T cells did not disappear. Furthermore, Tregs obtained OX40L from dendritic cells in an OX40-dependent manner in vitro and then suppressed OX40L expression in dendritic cells and Birc5 expression in Dsg3-specific T cells in vivo. Lastly, CRISPR/Cas9-mediated knockout of OX40 signaling in Dsg3-specific T cells restored their disappearance in Treg-ablated recipients. Thus, Treg-mediated peripheral deletion of autoreactive T cells operates as an OX40-dependent regulatory mechanism to avoid undesired autoimmunity besides thymic tolerance.

Forkhead box P3 (Foxp3)-positive intratumoral regulatory T (Treg) cells play critical roles in suppressing anti-tumor immune responses. It is reported that human tumors accumulate more Tregs than peripheral blood. However, it remains unclear whether intratumoral Tregs are primarily derived from Tregs in tumor-draining lymph nodes (dLNs) or are converted from conventional CD4+ T cells (Tconvs) in the transforming growth factor-beta -rich tumor microenvironment.Because each T-cell clone has its unique T-cell receptor (TCR), tracking the TCRs of the tumor Treg repertoire in the dLN Treg, dLN Tconv, and tumor Tconv enables us to identify the primary source of intratumoral Tregs. GFP+ hCD2+ CD25high and GFP- hCD2+ CD25int Tregs, which we defined as mature and immature Tregs, respectively, are distinguished from Tconvs in Foxp3-GDL Tg × Foxp3hCD2 Treg reporter mice having the Foxp3-GFP-diphtheria toxin receptor transgene and Foxp3-human CD2/CD52 knocked-in locus. On day 14 after subcutaneous injection of the Lewis lung carcinoma cell line, CD4+ Treg subsets and Tconvs in the tumor and dLN were collected for TCR sequencing, and the TCR repertoire overlap between these populations was quantified.We found that approximately 70%-80% of the Treg repertoire in the tumor overlapped with that in the dLN. Overlap between tumor Treg and tumor Tconv or dLN Tconv was at most 30% in tumor Tregs, significantly smaller than the tumor Treg-dLN Treg overlap. Moreover, single-cell TCR/RNA sequencing analysis exhibited that the tumor and dLN Treg clusters shared a significant number of T-cell clones, with few clones shared with tumor or dLN Tconv clusters. To examine whether dLN Tregs were the source of tumor Tregs even when they were actively repopulating, GFP+ mature Tregs were transiently depleted by administrating diphtheria toxin to tumor bearing mice. Mature tumor Tregs were completely depleted by day 2 and recovered rapidly through day 5 after DT administration. Analysis of the TCR repertoire of repopulated Treg and Tconv subsets revealed that repertoire overlap between tumor Treg and dLN or tumor Tconv was small and that tumor Treg-dLN Tregs overlap remained dominant, proposing that the repopulated intratumoral Tregs were also mainly derived from dLN Tregs. These results demonstrated that dLN-tumor mobilization was the primary source of intratumoral Tregs and that Tregs converted from Tconvs comprised only a small fraction of the intratumoral Tregs in our model. This finding suggests that Treg clones that suppress anti-tumor responses in the tumor also inhibit the priming of tumor-reactive T cells in the dLN, which can limit the efficacy of tumor site-specific Treg depletion therapy. Citation Format: Hiroyasu Aoki, Haruka Shimizu, Shigeyuki Shichino, Mikiya Tsunoda, Haru Ogiwara, Shohei Hori, Kouji Matsushima, Satoshi Ueha. Intratumoral regulatory T cell clones originate from the draining lymph nodes regulatory T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5630.

The mucosal surfaces are the first portals of entry for numerous infectious agents. Therefore, mucosal tissues contain the largest immune cell population in the body, tasked with preparing for, or reacting to, a broad range of infectious threats. Treg cells were initially discovered as the T-cell subsets existing in healthy animals that play essential roles in constitutively preventing the development of autoimmune disease and inflammatory bowel disease. The gut microbiota affects the number, function, and T-cell receptor repertoire of intestinal Treg cells. Having adapted to the barrier sites, mucosal Treg cells are phenotypically distinct from those found in other organs. Induced mucosal Treg cells then contribute to the constitutive suppression and prevention of aberrant immune reactions to innocuous environmental factors, such as commensal bacteria and dietary components. Treg cells play a nonredundant role in the maintenance of mucosal immune homeostasis, as illustrated by the fact that defects in the development and/or functional maturation of Treg cells lead to mucosal inflammation.

Disturbed balance between immune surveillance and tolerance may lead to poor clinical outcomes in some malignancies. In paired analyses of adenocarcinoma and normal mucosa from 142 patients, we found a significant increase of the CD4/CD8 ratio and accumulation of regulatory T cells (Tregs) within the adenocarcinoma. The increased frequency of Tregs correlated with the local infiltration and extension of the tumor. There was concurrent maturation arrest, upregulation of programmed death-1 expression, and functional impairment in CD8+ T cells (CTLs) isolated from the adenocarcinoma. Adenocarcinoma-associated Tregs directly inhibit the function of normal human CTLs in vitro. With histopathological analysis, Foxp3+ Tregs were preferentially located in stroma. Concurrent transcriptome analysis of epithelial cells, stromal cells, and T cell subsets obtained from carcinomatous and normal intestinal samples from patients revealed a distinct gene expression signature in colorectal adenocarcinoma–associated Tregs, with overexpression of CCR1, CCR8, and TNFRSF9, whereas their ligands CCL4 and TNFSF9 were found upregulated in cancerous epithelium. Overexpression of WNT2 and CADM1, associated with carcinogenesis and metastasis, in cancer-associated stromal cells suggests that both cancer cells and stromal cells play important roles in the development and progression of colorectal cancer through the formation of a tumor microenvironment. The identification of CTL anergy by Tregs and the unique gene expression signature of human Tregs and stromal cells in colorectal cancer patients may facilitate the development of new therapeutics against malignancies.

CD4+ CD25+ regulatory T cells (Treg), an essential subset for preventing autoimmune diseases, is implicated as a negative regulator in anti-tumor immunity. We found that metformin (Met) reduced tumor-infiltrating Treg (Ti-Treg), particularly the terminally-differentiated CD103+ KLRG1+ population, and also decreased effector molecules such as CTLA4 and IL-10. Met inhibits the differentiation of naïve CD4+ T cells into inducible Treg (iTreg) by reducing forkhead box P3 (Foxp3) protein, caused by mTORC1 activation that was determined by the elevation of phosphorylated S6 (pS6), a downstream molecule of mTORC1. Rapamycin and compound C, an inhibitor of AMP-activated protein kinase (AMPK) restored the iTreg generation, further indicating the involvement of mTORC1 and AMPK. The metabolic profile of iTreg, increased Glut1-expression, and reduced mitochondrial membrane-potential and ROS production of Ti-Treg aided in identifying enhanced glycolysis upon Met-treatment. The negative impact of Met on Ti-Treg may help generation of the sustained antitumor immunity., Highlights • Metformin downregulates CD4+ CD25+ regulatory T cells (Treg) in tumors but not in peripheral lymphoid tissues. • Metformin administration results in activation of mTORC1 in Treg in tumors. • Metformin administration results in elevation of glycolysis, while suppressing oxidative phosphorylation in Treg in tumors. CD4+ CD25+ regulatory T cells (Treg) is a negative regulator that inhibits T cell mediated anti-tumor immunity. Therefore, targeting Treg is one of the important therapeutic intervention in cancers. We found that metformin reduces Treg in the number and the function in tumors. Metabolism of Treg is usually dependent on oxidative phosphorylation through fatty acid oxidation (FAO). However, metformin treatment causes metabolic reprogramming of Treg toward the glycolysis, resulting in the failure in survival in tumors. Metformin as a metabolic modifier for Treg may contribute to generation of sustained anti-tumor immunity, combined with currently emerging cancer immunotherapy.

// Garima Garg 1 , Eirini Nikolouli 1 , Matthias Hardtke-Wolenski 2 , Aras Toker 1 , Naganari Ohkura 3,4 , Michael Beckstette 1 , Takahisa Miyao 5 , Robert Geffers 6 , Stefan Floess 1 , Norbert Gerdes 7,8 , Esther Lutgens 7,9 , Anke Osterloh 10 , Shohei Hori 5 , Shimon Sakaguchi 3,4 , Elmar Jaeckel 2 and Jochen Huehn 1 1 Department of Experimental Immunology, Helmholtz Centre for Infection Research, Braunschweig, Germany 2 Department of Gastroenterology, Hepatology, Endocrinology, Hannover Medical School, Hannover, Germany 3 Department of Experimental Immunology, World Premier International Immunology Frontier Research Center, Osaka University, Suita, Japan 4 Department of Experimental Pathology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto, Japan 5 Laboratory for Immune Homeostasis, RIKEN Center for Integrative Medical Sciences, Yokohama City, Kanagawa, Japan 6 Genome Analytics, Helmholtz Centre for Infection Research, Braunschweig, Germany 7 Institute for Cardiovascular Prevention, Ludwig-Maximilians-University, Munich, Germany 8 Division of Cardiology, Pulmonology, and Vascular Medicine Medical Faculty, University Hospital Dusseldorf, Dusseldorf, Germany 9 Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, AZ, Amsterdam, The Netherlands 10 Department of Immunology, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany Correspondence to: Jochen Huehn, email: // Keywords : regulatory T cells, thymic APCs, epigenetic modification, alloantigen-specificity, Immunology and Microbiology Section, Immune response, Immunity Received : October 15, 2016 Accepted : March 03, 2017 Published : March 15, 2017 Abstract 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.

The proteasome degradation machinery is essential for a variety of cellular processes including senescence and T-cell immunity. Decreased proteasome activity is associated with the aging process; however, the regulation of the proteasome in CD4+ T cells in relation to aging is unclear. Here, we show that defects in the induction of the proteasome in CD4+ T cells upon T-cell receptor (TCR) stimulation underlie T-cell senescence. Proteasome dysfunction promotes senescence-associated phenotypes, including defective proliferation, cytokine production and increased levels of PD-1+ CD44High CD4+ T cells. Proteasome induction by TCR signaling via MEK-, IKK- and calcineurin-dependent pathways is attenuated with age and decreased in PD-1+ CD44High CD4+ T cells, the proportion of which increases with age. Our results indicate that defective induction of the proteasome is a hallmark of CD4+ T-cell senescence.

PD-1 (programmed-death 1), an immune-inhibitory receptor required for immune self-tolerance whose deficiency causes autoimmunity with variable severity and tissue specificity depending on other genetic factors, is expressed on activated T cells, including the transcription factor FoxP3(+) Treg cells known to play critical roles in maintaining immune tolerance. However, whether PD-1 expression by the Treg cells is required for their immune regulatory function, especially in autoimmune settings, is still unclear. We found that mice with partial FoxP3 insufficiency developed early-onset lympho-proliferation and lethal autoimmune pancreatitis only when PD-1 is absent. The autoimmune phenotype was rescued by the transfer of FoxP3-sufficient T cells, regardless of whether they were derived from WT or PD-1-deficient mice, indicating that Treg cells dominantly protect against development of spontaneous autoimmunity without intrinsic expression of PD-1. The absence of PD-1 combined with partial FoxP3 insufficiency, however, led to generation of ex-FoxP3 T cells with proinflammatory properties and expansion of effector/memory T cells that contributed to the autoimmune destruction of target tissues. Altogether, the results suggest that PD-1 and FoxP3 work collaboratively in maintaining immune tolerance mostly through nonoverlapping pathways. Thus, PD-1 is modulating the activation threshold and maintaining the balance between regulatory and effector T cells, whereas FoxP3 is sufficient for dominant regulation through maintaining the integrity of the Treg function. We suggest that genetic or environmental factors that even moderately affect the expression of both PD-1 and FoxP3 can cause life-threatening autoimmune diseases by disrupting the T-cell homeostasis., 免疫のブレーキPD-1は、制御性T細胞との役割分担によって自己免疫性膵炎を抑制する. 京都大学プレスリリース. 2016-07-20.

Background We have previously reported an antigen-specific protocol to induce transplant tolerance and linked suppression to human embryonic stem cell (hESC)-derived tissues in immunocompetent mice through coreceptor and costimulation blockade. However, the exact mechanisms of acquired immune tolerance in this model have remained unclear. Methods We utilize the NOD.Foxp3 hCD2 reporter mouse line and an ablative anti-hCD2 antibody to ask if CD4+FOXP3+ regulatory T cells (Treg) are required for coreceptor and costimulation blockade-induced immune tolerance. We also perform genome-wide single-cell RNA-sequencing to interrogate Treg during immune rejection and tolerance and to indicate possible mechanisms involved in sustaining Treg function. Results We show that Treg are indispensable for tolerance induced by coreceptor and costimulation blockade as depletion of which with an anti-hCD2 antibody resulted in rejection of hESC-derived pancreatic islets in NOD.Foxp3 hCD2 mice. Single-cell transcriptomic profiling of 12,964 intragraft CD4+ T cells derived from rejecting and tolerated grafts reveals that Treg are heterogeneous and functionally distinct in the two outcomes of transplant rejection and tolerance. Treg appear to mainly promote chemotactic and ubiquitin-dependent protein catabolism during transplant rejection while seeming to harness proliferative and immunosuppressive function during tolerance. We also demonstrate that this form of acquired transplant tolerance is associated with increased proliferation and PD-1 expression by Treg. Blocking PD-1 signaling with a neutralizing anti-PD-1 antibody leads to reduced Treg proliferation and graft rejection. Conclusions Our results suggest that short-term coreceptor and costimulation blockade mediates immune tolerance to hESC-derived pancreatic islets by promoting Treg proliferation through engagement of PD-1. Our findings could give new insights into clinical development of hESC-derived pancreatic tissues, combined with immunotherapies that expand intragraft Treg, as a potentially sustainable alternative treatment for T1D.

Previous work has elegantly demonstrated that, unlike adult mammalian heart, the neonatal heart is able to regenerate after injury from postnatal day (P) 1 to 7. Recently, macrophages are found to be required in the repair process as depletion of which abolishes endogenous regenerative capability of the neonatal heart. Nevertheless, whether innate immunity alone is sufficient for neonatal heart regeneration is obscure. Here, we investigate a hitherto novel role of FOXP3+ regulatory T-cells (Treg) in neonatal heart regeneration. Unlike their wild type counterparts, NOD/SCID mice that are deficient for T-cells but innate immune cells including macrophages fail to regenerate their injured heart as early as P3. In wild type mice, both conventional CD4+ T-cells and Treg are recruited to cardiac muscle within the first week after injury. Treatment with the lytic anti-CD4 antibody that specifically depletes conventional CD4+ T-cells leads to reduced cardiac fibrosis; while treatment with the lytic anti-CD25 antibody that specifically depletes CD4+CD25hiFOXP3+ Treg contributes to increased fibrosis of the neonatal heart after injury. Moreover, adoptive transfer of Treg to NOD/SCID mice results in mitigated fibrosis and increased proliferation and function of cardiac muscle of the neonatal heart after injury. Mechanistically, single cell transcriptomic profiling reveals that Treg are a source of chemokines and cytokines that attract monocytes and macrophages previously known to drive neonatal heart regeneration. Furthermore, Treg directly promote proliferation of both mouse and human cardiomyocytes in a paracrine manner. Our findings uncover an unappreciated mechanism in neonatal heart regeneration; and offer new avenues for developing novel therapeutics targeting Treg-mediated heart regeneration.

The regulation of intestinal homeostasis by the immune system involves the dynamic interplay between gut commensal microbiota and resident immune cells. It is well known that a large and diverse lymphocyte antigen receptor repertoire enables the immune system to recognize and respond to a wide range of invading pathogens. There is also an emerging appreciation for a critical role the T-cell receptor (TCR) repertoire serves in the maintenance of peripheral tolerance by regulatory T cells (Tregs). Nevertheless, how the diversity of the TCR repertoire in Tregs affects intestinal homeostasis remains unknown. To address this question, we studied mice whose T cells express a restricted TCR repertoire. We observed the development of spontaneous colitis, accompanied by the induction of T-helper type 17 cells in the colon that is driven by gut commensal microbiota. We provide further evidence that a restricted TCR repertoire causes a loss of tolerogenicity to microbiota, accompanied by a paucity of peripherally derived, Helios(-) Tregs and hyperactivation of migratory dendritic cells. These results thus reveal a new facet of the TCR repertoire in which Tregs require a diverse TCR repitoire for intestinal homeostasis, suggesting an additional driving force in the evolutional significance of the TCR repertoire.

Objective Helios+FoxP3+CD4+ (Helios+) Treg cells are believed to be involved in the regulation of various autoimmune diseases; however, the regulatory mechanisms underlying the development of Helios+ Treg cells remain uncertain. This study was undertaken to elucidate the regulatory mechanisms of Helios expression in CD4+ T cells and its roles in transforming growth factor β (TGFβ)–induced Treg cell function. Methods We examined the expression of Helios in CD4+ T cells in patients with rheumatoid arthritis by DNA microarray analysis before and after treatment with biologic agents. We also examined the effect of interleukin-6 (IL-6) and TGFβ on Helios expression in CD4+ T cells in humans and mice. The effect of forced expression of Helios on murine induced Treg cell function was also examined. The role of FoxP3 in the induction and function of Helios was assessed by using CD4+ T cells from FoxP3-deficient scurfy mice. Results Tocilizumab, but not tumor necrosis factor (TNF) inhibitors or abatacept, increased Helios expression in CD4+ T cells in patients with a good response. IL-6 inhibited the TGFβ-induced development of Helios+ induced Treg cells in both humans and mice. Both cell-intrinsic FoxP3 expression and TGFβ signaling were required for Helios induction in murine induced Treg cells. The forced expression of Helios enhanced the expression of various Treg cell–related molecules and the suppressive function in murine induced Treg cells. Helios-mediated enhancement of the suppressive function of induced Treg cells was obvious in FoxP3-sufficient CD4+ T cells but not in FoxP3-deficient CD4+ T cells. Conclusion Our findings indicate that Helios enhances induced Treg cell function in cooperation with FoxP3.

Disturbed balance between immune surveillance and tolerance may lead to poor clinical outcomes in some malignancies. In paired analyses of adenocarcinoma and normal mucosa from 142 patients, we found a significant increase of the CD4/CD8 ratio and accumulation of regulatory T cells (Tregs) within the adenocarcinoma. The increased frequency of Tregs correlated with the local infiltration and extension of the tumor. There was concurrent maturation arrest, upregulation of programmed death-1 expression, and functional impairment in CD8

© The Author(s) 2017. This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/, Immunization leads to the formation of germinal centres (GCs) that contain both T follicular helper (Tfh) and T follicular regulatory (Tfr) cells. Whether T-cell receptor (TCR) specificity defines the differential functions of Tfh and Tfr cells is unclear. Here we show that antigen-specific T cells after immunization are preferentially recruited to the GC to become Tfh cells, but not Tfr cells. Tfh cells, but not Tfr cells, also proliferate efficiently on restimulation with the same immunizing antigen in vitro. Ex vivo TCR repertoire analysis shows that immunization induces oligoclonal expansion of Tfh cells. By contrast, the Tfr pool has a TCR repertoire that more closely resembles that of regulatory T (Treg) cells. Our data thus indicate that the GC Tfh and Tfr pools are generated from distinct TCR repertoires, with Tfh cells expressing antigen-responsive TCRs to promote antibody responses, and Tfr cells expressing potentially autoreactive TCRs to suppress autoimmunity., The research was funded by Fundação para Ciência e Tecnologia (FCT) grants PTDC/SAU-IMU/120225/2010, HMSP-ICT/0034/2013 and FCT-FAPESP/19906/2014 (to L.G.). A.R.M. and S.C.P.A. are funded by FCT scholarships SFRH/BD/88030/2012 and SFRH/BDP/81391/2011, respectively. The work by D.K., A.S., E.M.-F., W.C. and F.J. has been funded by Assistance Publique-Hôpitaux de Paris, Université Pierre and Marie Curie (Paris VI), LabEx Transimmunom (ANR-11-IDEX-0004-02) and ERC Advanced Grant TRiPoD (322856). The work by J.F. has been supported by PIRSES-GA-2012-317893 (7th FP, EU) and BIOCAPS (FP7/REGPOT-2012-2013.1, EC) under grant agreement no. 316265.

Summary Foxp3 controls the development and function of regulatory T (Treg) cells, but it remains elusive how Foxp3 functions in vivo. Here, we established mouse models harboring three unique missense Foxp3 mutations that were identified in patients with the autoimmune disease IPEX. The I363V and R397W mutations were loss-of-function mutations, causing multi-organ inflammation by globally compromising Treg cell physiology. By contrast, the A384T mutation induced a distinctive tissue-restricted inflammation by specifically impairing the ability of Treg cells to compete with pathogenic T cells in certain non-lymphoid tissues. Mechanistically, repressed BATF expression contributed to these A384T effects. At the molecular level, the A384T mutation altered Foxp3 interactions with its specific target genes including Batf by broadening its DNA-binding specificity. Our findings identify BATF as a critical regulator of tissue Treg cells and suggest that sequence-specific perturbations of Foxp3-DNA interactions can influence specific facets of Treg cell physiology and the immunopathologies they regulate.

SummaryT cell receptor (TCR) signaling driven by interaction of the TCR with specific complexes of self-peptide and the major histocompatibility complex determines T cell fate in thymic development. However, the signaling pathway through which TCR signal strength regulates distinct T cell lineages remains unknown. Here we have used mice lacking the endoplasmic reticulum Ca2+ sensors stromal interaction molecule 1 (STIM1) and STIM2 to show that STIM-induced store-operated Ca2+ entry is not essential for thymic development of conventional TCRαβ+ T cells but is specifically required for the development of agonist-selected T cells (regulatory T cells, invariant natural killer T cells, and TCRαβ+ CD8αα+ intestinal intraepithelial lymphocytes). The severe impairment of agonist-selected T cell development is mainly due to a defect in interleukin-2 (IL-2) or IL-15 signaling. Thus, STIM1 and STIM2-mediated store-operated Ca2+ influx, leading to efficient activation of NFAT (nuclear factor of activated T cells), is critical for the postselection maturation of agonist-selected T cells.

Stable expression of Foxp3 in regulatory T cells (Tregs) depends on DNA demethylation at the Treg-specific demethylated region (TSDR), a conserved, CpG-rich region within the Foxp3 locus. The TSDR is selectively demethylated in ex vivo Tregs purified from secondary lymphoid organs, but it is unclear at which stage of Treg development demethylation takes place. In this study, we show that commitment to a stable lineage occurred during early stages of murine thymic Treg development by engraving of lineage-specific epigenetic marks in parallel with establishment of a Treg-specific gene expression profile. TSDR demethylation was achieved through an active mechanism and involved enzymes of the ten-eleven-translocation family and hydroxylation of methylated cytosines, a modification that is implicated as an initiating step of mitosis-independent DNA demethylation pathways and has not yet been observed at specific loci during immune cell differentiation. Together, our results demonstrate that initiating TSDR demethylation during early stages of thymic Treg development commences stabilization of Foxp3 expression and guarantees full functionality and long-term lineage stability of Tregs.

Tregs play an important role in protecting the skin from autoimmune attack. However, the extent of Treg trafficking between the skin and draining lymph nodes (DLNs) is unknown. We set out to investigate this using mice engineered to express the photoconvertible fluorescence protein Kaede, which changes from green to red when exposed to violet light. By exposing the skin of Kaede-transgenic mice to violet light, we were able to label T cells in the periphery under physiological conditions with Kaede-red and demonstrated that both memory phenotype CD4+Foxp3- non-Tregs and CD4+Foxp3+ Tregs migrated from the skin to DLNs in the steady state. During cutaneous immune responses, Tregs constituted the major emigrants and inhibited immune responses more robustly than did LN-resident Tregs. We consistently observed that cutaneous immune responses were prolonged by depletion of endogenous Tregs in vivo. In addition, the circulating Tregs specifically included activated CD25hi Tregs that demonstrated a strong inhibitory function. Together, our results suggest that Tregs in circulation infiltrate the periphery, traffic to DLNs, and then recirculate back to the skin, contributing to the downregulation of cutaneous immune responses.

Immune responses are crucial not only for host defence against pathogens but also for tissue maintenance and repair after injury. Lymphocytes are involved in the healing process after tissue injury, including bone fracture and muscle damage. However, the specific immune cell subsets and mediators of healing are not entirely clear. Here we show that γδ T cells produce IL-17A, which promotes bone formation and facilitates bone fracture healing. Repair is impaired in IL-17A-deficient mice due to a defect in osteoblastic bone formation. IL-17A accelerates bone formation by stimulating the proliferation and osteoblastic differentiation of mesenchymal progenitor cells. This study identifies a novel role for IL-17-producing γδ T cells in skeletal tissue regeneration., γδ T cells are innate-like lymphocytes that regulate immune responses by producing IL-17A or IFN-γ, but have no known role in bone healing. Here the authors show a nonimmune bone-regenerative function of IL-17A produced by the Vγ6+ subset in mice.

SummaryThe emerging notion of environment-induced reprogramming of Foxp3+ regulatory T (Treg) cells into helper T (Th) cells remains controversial. By genetic fate mapping or adoptive transfers, we have identified a minor population of nonregulatory Foxp3+ T cells exhibiting promiscuous and transient Foxp3 expression, which gave rise to Foxp3− (“exFoxp3”) Th cells and selectively accumulated in inflammatory cytokine milieus or in lymphopenic environments including those in early ontogeny. In contrast, Treg cells did not undergo reprogramming under those conditions irrespective of their thymic or peripheral origins. Moreover, although a few Treg cells transiently lose Foxp3 expression, such “latent” Treg cells retained their memory and robustly re-expressed Foxp3 and suppressive function upon activation. This study establishes that Treg cells constitute a stable cell lineage, whose committed state in a changing environment is ensured by DNA demethylation of the Foxp3 locus irrespectively of ongoing Foxp3 expression.

Regulatory T cells (Tregs), a subset of CD4(+) helper T cells, are crucial for immunological self-tolerance. Defect in development or function of Tregs results in autoimmune disease in human and mice. Whereas it is known that Tregs mainly develop in the thymus, the molecular mechanism underlying development of Treg is not fully understood. TRAF6-deficient mice showed a severe defect in the Treg development in thymus. In vitro fetal thymic organ culture experiments indicated that the defect is ascribed to the absence of TRAF6 in thymic cells. Moreover, mixed fetal liver transfer experiments revealed that the development of Foxp3(+) cells differentiated from Traf6(-/-) hematopoietic cells was specifically impaired in the thymus, indicating cell-intrinsic requirement for TRAF6 in the Treg development. On the other hand, TRAF6 is not required for the development of conventional CD4(+) T cell. In addition, TGFβ-dependent induction of Foxp3 in CD4(+) T cells in vitro was not impaired by the absence of TRAF6. Overall, our data indicate that TRAF6 plays an essential role on the commitment of immature thymocytes to thymic Tregs in cell-intrinsic fashion.

We have recently described two independent mouse models in which the administration of diphtheria toxin (DT) leads to specific depletion of regulatory T cells (Tregs) due to expression of DT receptor-enhanced GFP under the control of the Foxp3 promoter. Both mouse models develop severe autoimmune disorders when Foxp3+ Tregs are depleted. Those findings were challenged in a recent study published in this journal suggesting the expression of Foxp3 in epithelial cells as the cause for disease development. By using genetic, cellular, and immunohistochemical approaches, we do not find evidence for Foxp3-expression in nonhematopoietic cells. DT injection does not lead to a loss of epithelial integrity in our Foxp3-DTR models. Instead, Foxp3 expression is Treg-specific and ablation of Foxp3+ Tregs leads to the induction of fatal autoimmune disorders. Autoimmunity can be reversed by the adoptive transfer of Tregs into depleted hosts, and the transfer of Foxp3-deficient bone marrow into T cell-deficient irradiated recipients leads to full-blown disease development.

Most of the immunoglobulin A (IgA) in the gut is generated by B cells in the germinal centers of Peyer's patches through a process that requires the presence of CD4 + follicular B helper T(T FH ) cells. The nature of these T FH cells in Peyer's patches has been elusive. Here, we demonstrate that suppressive Foxp3 + CD4 + T cells can differentiate into T FH cells in mouse Peyer's patches. The conversion of Foxp3 + T cells into T FH cells requires the loss of Foxp3 expression and subsequent interaction with B cells. Thus, environmental cues present in gut Peyer's patches promote the selective differentiation of distinct helper T cell subsets, such as T FH cells.

Non-obese diabetic (NOD) mice that are genetically deficient in either IFN-gamma or beta chain of the IFN-gammaR develop diabetes with similar kinetics to wild-type NOD mice. In the current study, we demonstrated that treatment of IFN-gamma signaling-deficient NOD mice with cyclophosphamide (CY) not only fails to induce acute diabetes but also confers permanent protection from diabetes. Protection was mediated by the preferential generation of regulatory T cells (Treg cells) that are capable of suppressing the diabetogenic process, with no change in the total number and function of Treg cells. Moreover, CY treatment of IFN-gamma signaling-deficient NOD mice reversed the ongoing pathogenic process and eliminated cellular infiltrates of pancreatic islets. While these results have been derived using a genetically modified mouse model of diabetes, they indicate that knowledge of host genetic factors and environmental factors influencing the development of Type I diabetes mellitus may provide a rational approach to develop a means to reverse the development of Type I diabetes in human.

The cytokine, transforming growth factor-beta1 (TGF-beta1), converts naive T cells into regulatory T cells that prevent autoimmunity. However, in the presence of interleukin (IL)-6, TGF-beta1 has also been found to promote differentiation into IL-17-producing helper T (Th17) cells that are deeply involved in autoimmunity and inflammation. However, it has not been clarified how TGF-beta1 and IL-6 determine such a distinct fate. Here we found that a master regulator for Th17, retinoic acid-related orphan receptor gammat (RORgammat), was rapidly induced by TGF-beta1 regardless of the presence of IL-6. IL-6 reduced Foxp3 expression, and overexpression of Foxp3 in a T cell line resulted in a strong reduction of IL-17A expression. We have characterized the IL-17A promoter and found that RORgammat binding is sufficient for activation of the minimum promoter in the HEK 293T cells. RORgammat-mediated IL-17A promoter activation was suppressed by forced expression of Foxp3. Foxp3 directly interacted with RORgammat through exon 2 region of Foxp3. The exon 2 region and forkhead (FKH) domain of Foxp3 were necessary for the suppression of RORgammat-mediated IL-17A promoter activation. We propose that induction of Foxp3 is the mechanism for the suppression of Th17 and polarization into inducible Treg.