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In the thymus, the T lymphocyte repertoire is purged of a substantial portion of highly self-reactive cells. This negative selection process relies on the strength of TCR-signaling in response to self-peptide-MHC complexes, both in the cortex and medulla regions. However, whether cytokine-signaling contributes to negative selection remains unclear. Here, we report that, in the absence of Transforming Growth Factor beta (TGF-β) signaling in thymocytes, negative selection is significantly impaired. Highly autoreactive thymocytes first escape cortical negative selection and acquire a Th1-like-phenotype. They express high levels of CXCR3, aberrantly accumulate at the cortico-medullary junction and subsequently fail to sustain AIRE expression in the medulla, escaping medullary negative selection. Highly autoreactive thymocytes undergo an atypical maturation program, substantially accumulate in the periphery and induce multiple organ-autoimmune-lesions. Thus, these findings reveal TGF-β in thymocytes as crucial for negative selection with implications for understanding T cell self-tolerance mechanisms., TGFβ is critical for limiting autoreactive responses of peripheral T cells. Here, the authors show that TGFβ signaling in thymocytes mediates elimination of self-reactive T cells and promotes the expression of self-antigens by medullary thymic epithelial cells.

Suppressive regulatory T cell (Treg) differentiation is controlled by diverse immunometabolic signaling pathways and intracellular metabolites. Here we show that cell-permeable α-ketoglutarate (αKG) alters the DNA methylation profile of naive CD4 T cells activated under Treg polarizing conditions, markedly attenuating FoxP3+ Treg differentiation and increasing inflammatory cytokines. Adoptive transfer of these T cells into tumor-bearing mice results in enhanced tumor infiltration, decreased FoxP3 expression, and delayed tumor growth. Mechanistically, αKG leads to an energetic state that is reprogrammed toward a mitochondrial metabolism, with increased oxidative phosphorylation and expression of mitochondrial complex enzymes. Furthermore, carbons from ectopic αKG are directly utilized in the generation of fatty acids, associated with lipidome remodeling and increased triacylglyceride stores. Notably, inhibition of either mitochondrial complex II or DGAT2-mediated triacylglyceride synthesis restores Treg differentiation and decreases the αKG-induced inflammatory phenotype. Thus, we identify a crosstalk between αKG, mitochondrial metabolism and triacylglyceride synthesis that controls Treg fate. ispartof: CELL REPORTS vol:37 issue:5 ispartof: location:United States status: published

Despite the lack of unanimous consent on hematopoietic cell development, the current paradigm is that early hematopoietic progenitors are exclusively embryonic and short-lived. Their progeny resides in the adult and maintains its homeostasis exclusively by self-renewing without de novo generation. Here, we show that hematopoietic progenitor cells (HPC), which passed through a CD4 positive stage (HPC-CD4) give rise to a fraction of {gamma}{delta}T cells, B cells, and dendritic cells, a larger part of liver and lung macrophages, and megakaryocyte-erythroblast progenitors. These hematopoietic progenitor cells emerged during embryonic life, are observed but not generated in adults, where their graft allows the production of myeloid and lymphoid cells. Thus, we propose HPC-CD4 as a distinct embryonic HPC, which maintains a continuous generation of a fraction of hematopoietic cells through the lifespan.

SMAD4, a key mediator of TGF-β signaling, plays a crucial role in T cells to prevent chronic gut inflammation. However, the molecular mechanisms underlying this control remain elusive. Using different genetic and epigenetic approaches, we unexpectedly reveal that SMAD4 in CD8 T cells prevents chronic intestinal inflammation by a feedforward mechanism that is TGF-β-independent. Prior to any TGF-β-receptor engagement, SMAD4 acts as an active and basal repressor of epigenetic, transcriptional and functional TGF-β imprinting in CD8 T cells. Thus, in sharp opposition to total TGF-β signaling deletion, SMAD4 deletion impairs naïve CD8 T cell effector predisposition but promotes CD8 T cell accumulation and epithelial retention by promoting their response to IL-7 and their expression of integrins such as Itgae. Besides, SMAD4 deletion unleashes the induction of a wide range of TGF-β-signaling-repressors such as Smad7, Ski, Skil, and Smurf2 and hampers TGF-β-mediated CD8 T cell immunosuppression. Mechanistically, prior to any TGF-β signal, SMAD4 binds to the loci of several TGF-β-target genes, and by regulating histone acetylation, represses their expression. The massive gut epithelial colonization, associated with their escape from the immunoregulatory TGF-β effects overtakes their poor effector preconditioning and elicits microbiota-driven chronic epithelial CD8 T cell activation. Hence, in an anticipatory manner, independently of TGF-β, SMAD4 governs a feedforward regulation of TGF-β effects in CD8 T cells, preventing chronic intestinal inflammation.

© The Author(s), under exclusive licence to Springer Nature America, Inc. 2020, Tissue-resident memory T (TRM) cells, functionally distinct from circulating memory T cells, have a critical role in protective immunity in tissues, are more efficacious when elicited after vaccination and yield more effective antitumor immunity, yet the signals that direct development of TRM cells are incompletely understood. Here we show that type 1 regulatory T (Treg) cells, which express the transcription factor T-bet, promote the generation of CD8+ TRM cells. The absence of T-bet-expressing type 1 Treg cells reduces the presence of TRM cells in multiple tissues and increases pathogen burden upon infectious challenge. Using infection models, we show that type 1 Treg cells are specifically recruited to local inflammatory sites via the chemokine receptor CXCR3. Close proximity with effector CD8+ T cells and Treg cell expression of integrin-β8 endows the bioavailability of transforming growth factor-β in the microenvironment, thereby promoting the generation of CD8+ TRM cells., The project leading to these results has received funding from the European Union H2020 ERA project (no. 667824, EXCELLtoINNOV), Fundo iMM-Laço and ‘la caixa’ Foundation (ID 100010434) under agreement LCF/PR/HR19/52160005 for work in the Veldhoen laboratory, with additional funding from the Fundação para a Ciência e a Tecnologia to P.F.-C. (SFRH/BD/131605/2017), to L.B. (PD/BD/138847/2018) and to A.B. (SFRH/BD/138900/2018). In addition, the work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) SFB1366 (project no. 394046768-SFB 1366; C02) and by SPP 1937 (CE 140/2-1) to A.C and SFB1292 (TP13) and TR156 (TPB02) to H.C.P. A.L. was supported by Ligue Nationale Contre le Cancer. Other grants supporting this study: Foncer Contre le Cancer (JCM) and EL-2016 LNCC Labelisation Ligue Nationale Contre Cancer.

Summary T helper-17 (Th17) cells are associated with inflammatory disorders and cancer. We report that environmental conditions resulting in cellular stress, such as low oxygen, glucose, and isotonic stress, particularly enhance the generation of Th17 cells. Pharmacological inhibition of cell stress reduces Th17 cell differentiation while stress inducers enhance the development of Th17 cells. The cellular stress response results in Th17 cell development via sustained cytoplasmic calcium levels and, in part, XBP1 activity. Furthermore, in an inflammatory environment, conditions resulting in cell stress can bring about de novo Th17 cell differentiation, even in the absence of transforming growth factor β (TGF-β) signaling. In vivo, cell stress inhibition enhances resistance to Th17-mediated autoimmunity while stress-exposed T cells enhance disease severity. Adverse metabolic environments during inflammation provide a link between adaptive immunity and inflammation and may represent a risk factor for the development of chronic inflammatory conditions by facilitating Th17 cell differentiation., Graphical Abstract, Highlights • Limited metabolite availability results in cellular stress • Cellular stress enhances Th17 cell polarization • Cellular stress induces de novo Th17 cell differentiation • Cellular stress can substitute for TGF-β in Th17 cell differentiation, Brucklacher-Waldert et al. show how environmental conditions resulting in cellular stress, such as low metabolite levels, specifically enhance Th17 cell differentiation. Under inflammatory conditions, this stress can substitute for TGF-β signaling resulting in de novo Th17 cell differentiation.

T follicular helper (Tfh) cells contribute to the establishment of humoral immunity by controlling the delivery of helper signals to activated B cells; however, Tfh development must be restrained, as aberrant accumulation of these cells is associated with positive selection of self-reactive germinal center B cells and autoimmunity in both humans and mice. Here, we show that TGF-β signaling in T cells prevented Tfh cell accumulation, self-reactive B cell activation, and autoantibody production. Using mice with either T cell–specific loss or constitutive activation of TGF-β signaling, we demonstrated that TGF-β signaling is required for the thymic maturation of CD44+CD122+Ly49+CD8+ regulatory T cells (Tregs), which induce Tfh apoptosis and thus regulate this cell population. Moreover, peripheral Tfh cells escaping TGF-β control were resistant to apoptosis, exhibited high levels of the antiapoptotic protein BCL2, and remained refractory to regulation by CD8+ Tregs. The unrestrained accumulation of Tfh cells in the absence of TGF-β was dependent on T cell receptor engagement and required B cells. Together, these data indicate that TGF-β signaling restrains Tfh cell accumulation and B cell–associated autoimmunity and thereby controls self-tolerance.

International audience; Transforming growth factor-beta (TGF-beta) is a major immunosuppressive cytokine that maintains immune homeostasis and prevents autoimmunity through its antiproliferative and anti-inflammatory properties in various immune cell types. We provide genetic, pharmacologic, and biochemical evidence that a critical target of TGF-beta signaling in mouse and human natural killer (NK) cells is the serine and threonine kinase mTOR (mammalian target of rapamycin). Treatment of mouse or human NK cells with TGF-beta in vitro blocked interleukin-15 (IL-15)-induced activation of mTOR. TGF-beta and the mTOR inhibitor rapamycin both reduced the metabolic activity and proliferation of NK cells and reduced the abundances of various NK cell receptors and the cytotoxic activity of NK cells. In vivo, constitutive TGF-beta signaling or depletion of mTOR arrested NK cell development, whereas deletion of the TGF-beta receptor subunit TGF-betaRII enhanced mTOR activity and the cytotoxic activity of the NK cells in response to IL-15. Suppression of TGF-beta signaling in NK cells did not affect either NK cell development or homeostasis; however, it enhanced the ability of NK cells to limit metastases in two different tumor models in mice. Together, these results suggest that the kinase mTOR is a crucial signaling integrator of pro- and anti-inflammatory cytokines in NK cells. Moreover, we propose that boosting the metabolic activity of antitumor lymphocytes could be an effective strategy to promote immune-mediated tumor suppression

NUPR1 (nuclear protein 1), also called P8 (molecular mass 8 kDa) or COM1 (candidate of metastasis 1), is involved in the stress response and in cancer progression. In the present study, we investigated whether human NUPR1 expression was regulated by TGFβ (transforming growth factor β), a secreted polypeptide largely involved in tumorigenesis. We demonstrate that the expression of NUPR1 was activated by TGFβ at the transcriptional level. We show that this activation is mediated by the SMAD proteins, which are transcription factors specifically involved in the signalling of TGFβ superfamily members. NUPR1 promoter analysis reveals the presence of a functional TGFβ-response element binding the SMAD proteins located in the genomic DNA region corresponding to the 5′-UTR (5′-untranslated region). Altogether, the molecular results of the present study, which demonstrate the existence of a TGFβ/SMAD/NUPR1 activation cascade, open the way to consider and investigate further a new mechanism enabling TGFβ to promote tumorigenesis by inducing stress resistance.

Invariant natural killer T (iNKT) cells have the ability to rapidly secret cytokines in response to diverse stimuli, and therefore influence numerous immune reactions. Although IFN-γ and IL-4 are thought to dominate iNKT cytokine production, a distinct subset of iNKT cells, expressing RORγt and producing IL-17, has now been identified in both mice and humans. Although a role in pathogen and allergic responses has been assigned to the RORγt+ iNKT subset, factors controlling their development and function remain illusive. Here, we demonstrate that RORγt+ iNKT-cell differentiation obeys transforming growth factor-β (TGF-β) signaling control, different from that described for conventional iNKT cells. We reveal that TGF-β signaling, and particularly its SMAD4-dependent pathway, is required for both the survival of RORγt+ iNKT cells during their development and IL-17 production at the periphery. Moreover, constitutive TGF-β signaling in RORγt+ iNKT cells drives higher peripheral numbers and increased tissue distribution. Finally, we found that SMAD4-dependent TGF-β signaling is mandatory for the peripheral expansion of the RORγt+ iNKT cells responding to inflammatory signals. Thus, this work demonstrates that both the development and responsiveness of the newly described IL-17–producing iNKT cell subset is under the control of a dedicated TGF-β signaling pathway.

We have previously generated a transgenic mouse strain (LSL-TβRICA) containing a Cre-inducible constitutively active TGFβ type I receptor (Bartholin L. et al. 2008. Generation of mice with conditionally activated transforming growth factor beta signaling through the TbetaRI/ALK5 receptor, GENESIS). Transgene expression depends on the excision of a floxed-transcriptional STOP (LSL, Lox-STOP-Lox) located upstream the TβRICA coding sequence. In order to evaluate the correct excision of the STOP signal in the presence of Cre-recombinase, we developed a rapid screening based on an original PCR genotyping strategy. More precisely, we designed a set of primers flanking the LSL containing region. The size of the amplified products will differ according to recombination status of the LSL-TβRICA allele. Indeed, the size of the STOP containing PCR product is 1.93 kb, but is reduced to 0.35 kb when the STOP signal is removed after Cre-mediated recombination. We validated excision in several compartments, including pancreas, liver, T lymphocytes and embryos using different Cre expressing transgenic mouse strains. This represents a simple and efficient way of monitoring the tissue specific recombination of the LSL-TβRICA allele.

We generated a transgenic mouse strain (LSL-TβRICA) containing a latent constitutively active TGFβ type I receptor (TβRI/ALK5) by using a knock-in strategy into the X chromosome-linked hypoxanthine phosphoribosyl-transferase (Hprt) locus. Transgene expression, under the control of the ubiquitous CAG (human cytomegalovirus enhancer and chicken β-actin) promoter, is repressed by a floxed transcriptional “Stop” (LSL, Lox-Stop-Lox). In the presence of cre-recombinase, the “Stop” is excised to allow TβRICA transgene expression. We showed that restricted expression of TβRICA in T lymphocytes efficiently activates TGFβ signaling and rescues the T-cell autoimmune disorders of TGFβRII conditional knockouts. Unexpectedly, our study reveals that TGFβ signaling upregulation controls T-cell activation but does not impair their development or their peripheral homeostasis. In addition to the information provided on TGFβ effects on T-cell biology, LSL-TβRICA mouse constitutes an attractive tool to address the effect of TGFβ signaling upregulation in any cell type expressing the cre-recombinase. genesis 46:724–731, 2008. Published 2008 Wiley-Liss, Inc.

T cell activation requires that the cell meet increased energetic and biosynthetic demands. We showed that exogenous nutrient availability regulated the differentiation of naive CD4(+) T cells into distinct subsets. Activation of naive CD4(+) T cells under conditions of glutamine deprivation resulted in their differentiation into Foxp3(+) (forkhead box P3-positive) regulatory T (Treg) cells, which had suppressor function in vivo. Moreover, glutamine-deprived CD4(+) T cells that were activated in the presence of cytokines that normally induce the generation of T helper 1 (TH1) cells instead differentiated into Foxp3(+) Treg cells. We found that alpha-ketoglutarate (alphaKG), the glutamine-derived metabolite that enters into the mitochondrial citric acid cycle, acted as a metabolic regulator of CD4(+) T cell differentiation. Activation of glutamine-deprived naive CD4(+) T cells in the presence of a cell-permeable alphaKG analog increased the expression of the gene encoding the TH1 cell-associated transcription factor Tbet and resulted in their differentiation into TH1 cells, concomitant with stimulation of mammalian target of rapamycin complex 1 (mTORC1) signaling. Together, these data suggest that a decrease in the intracellular amount of alphaKG, caused by the limited availability of extracellular glutamine, shifts the balance between the generation of TH1 and Treg cells toward that of a Treg phenotype.

We have shown previously that peripheral lymph node-resident retinoic acid receptor-related orphan receptor γt+ NK1.1− invariant NKT (iNKT) cells produce IL-17A independently of IL-6. In this study, we show that the concomitant presence of IL-1 and IL-23 is crucial to induce a rapid and sustained IL-17A/F and IL-22 response by these cells that requires TCR–CD1d interaction and partly relies on IL-23–mediated upregulation of IL-23R and IL-1R1 expression. We further show that IL-1 and IL-23 produced by pathogen-associated molecular pattern-stimulated dendritic cells induce this response from NK1.1− iNKT cells in vitro, involving mainly TLR2/4-signaling pathways. Finally, we found that IL-17A production by these cells occurs very early and transiently in vivo in response to heat-killed bacteria. Overall, our study indicates that peripheral lymph node NK1.1− iNKT cells could be a source of innate Th17-related cytokines during bacterial infections and supports the hypothesis that they are able to provide an efficient first line of defense against bacterial invasion.

International audience; Invariant natural killer T (iNKT) cells constitute a distinct subset of T lymphocytes exhibiting important immune-regulatory functions. Although various steps of their differentiation have been well characterized, the factors controlling their development remain poorly documented. Here, we show that TGF-beta controls the differentiation program of iNKT cells. We demonstrate that TGF-beta signaling carefully and specifically orchestrates several steps of iNKT cell development. In vivo, this multifaceted role of TGF-beta involves the concerted action of different pathways of TGF-beta signaling. Whereas the Tif-1gamma branch controls lineage expansion, the Smad4 branch maintains the maturation stage that is initially repressed by a Tif-1gamma/Smad4-independent branch. Thus, these three different branches of TGF-beta signaling function in concert as complementary effectors, allowing TGF-beta to fine tune the iNKT cell differentiation program.