A distal Foxp3 enhancer enables interleukin-2 dependent thymic Treg cell lineage commitment for robust immune tolerance

The regulation and differentiation of regulatory T cells and their dysfunction in autoimmune diseases

The discovery of FOXP3+ regulatory T (Treg) cells as a distinct cell lineage with a central role in regulating immune responses provided a deeper understanding of self-tolerance. The transcription factor FOXP3 serves a key role in Treg cell lineage determination and maintenance, but is not sufficient to enable the full potential of Treg cell suppression, indicating that other factors orchestrate the fine-tuning of Treg cell function. Moreover, FOXP3-independent mechanisms have recently been shown to contribute to Treg cell dysfunction. FOXP3 mutations in humans cause lethal fulminant systemic autoinflammation (IPEX syndrome). However, it remains unclear to what degree Treg cell dysfunction is contributing to the pathophysiology of common autoimmune diseases. In this Review, we discuss the origins of Treg cells in the periphery and the multilayered mechanisms by which Treg cells are induced, as well as the FOXP3-dependent and FOXP3-independent cellular programmes that maintain the suppressive function of Treg cells in humans and mice. Further, we examine evidence for Treg cell dysfunction in the context of common autoimmune diseases such as multiple sclerosis, inflammatory bowel disease, systemic lupus erythematosus and rheumatoid arthritis.

Association of CTACK, IL-2, and IL-13 with increased risk of lung cancer: A Mendelian randomization study

BACKGROUND

In recent years, relevant studies have reported that inflammatory cytokines are related to the occurrence of cancer. However, the correlation with lung cancer is not clear. This study used the Mendelian random grouping method to investigate the correlation between inflammatory factors and lung cancer in different populations.

METHODS

We obtained the single nucleotide polymorphisms (SNPs) of inflammatory cytokines through the open database and the SNPs of lung cancer (European and East Asian) through the IEU OpenGWAS project. Inverse variance-weighted (IVW) MR analyses were used to determine the causalities of exposures and outcomes. Supplementary analyses were also performed using weighted median and MR-Egger regressions. Afterward, sensitivity analyses were performed to test the robustness. Search the ChEMBL database for target drugs and indications for CTACK, IL-2, and IL-13.

RESULTS

By IVW method, we found that CTACK, IL-2, and IL-13 were associated with an increased risk of lung cancer in the European population (CTACK, OR = 1.098, 95 % CI 1.001-1.204, P = 0.047; IL-2, OR = 1.112, 95 % CI 1.009-1.225, P = 0.032; IL-13, OR = 1.068, 95 % CI 1.007-1.132, P = 0.029), while only IL-13 was associated with an increased risk of lung cancer in the East Asian population (IL-13, OR = 1.110, 95 % CI 1.010-1.220, P = 0.030). The weighted median and MR-Egger regression methods were in the same direction as the IVW effect sizes. Furthermore, no evidence of multidirectionality was detected using the MR-Egger intercept as a sensitivity analysis. Currently, there are no approved or phase III studied indications for CTACK, IL-2, and IL-13 targets in lung cancer.

CONCLUSION

The study outcomes supported that the inflammatory cytokines CTACK, IL-2, and IL-13 increase the risk of lung cancer. There is a lack of indications for drugs in these three targets. We explored the causal relationship between inflammatory cytokines and lung cancer, providing a basis for future cancer prediction models and targets for anti-tumor therapy.

ADENOSINE INFLUENCES FOXP3 EXPRESSION OF T REGS VIA THE A2AR/CREB PATHWAY IN A MOUSE MODEL OF SEPSIS

ABSTRACT

The adenosine concentration and forkhead box protein (Foxp3) expression in T regulatory cells (T regs ) are increased during sepsis. However, the mechanism by which adenosine induces Foxp3 expression is incompletely understood. A cecal ligation and puncture (CLP) model was constructed using C57BL/J mice. The plasma adenosine concentration and Foxp3 expression in splenic T regs were increased consistently for 15 days after sepsis onset. Analysis of the mean fluorescence intensity of Foxp3 and adenosine concentration in the same mice revealed a linear correlation. In the CLP model, adenosine 2a receptor (A2aR) blockade inhibited Foxp3 expression in T regs . In vitro activation of A2aR promoted Foxp3 expression in T regs and facilitated secretion of extracellular vesicles. Transcriptome sequencing revealed that A2aR blockade led to changes in cyclic adenosine monophosphate response element-binding protein (CREB) transcription in T regs in our sepsis model. Use of adenosine or A2aR agonists promoted CREB expression, CREB phosphorylation at S133, T reg expression of Foxp3, and enhanced inhibition of proliferation of cluster of differentiation (CD)4+ lymphocytes. A2aR blockade or inhibition of CREB expression inhibited Foxp3 expression in T regs . In the CLP model, use of CREB inhibitors could inhibit Foxp3 expression and reduce the bacterial load. In summary, adenosine in sepsis promotes CREB phosphorylation via A2aR which, in turn, upregulates Foxp3 expression in T regs .

Deciphering the developmental trajectory of tissue-resident Foxp3+ regulatory T cells

Foxp3+ TREG cells have been at the focus of intense investigation for their recognized roles in preventing autoimmunity, facilitating tissue recuperation following injury, and orchestrating a tolerance to innocuous non-self-antigens. To perform these critical tasks, TREG cells undergo deep epigenetic, transcriptional, and post-transcriptional changes that allow them to adapt to conditions found in tissues both at steady-state and during inflammation. The path leading TREG cells to express these tissue-specialized phenotypes begins during thymic development, and is further driven by epigenetic and transcriptional modifications following TCR engagement and polarizing signals in the periphery. However, this process is highly regulated and requires TREG cells to adopt strategies to avoid losing their regulatory program altogether. Here, we review the origins of tissue-resident TREG cells, from their thymic and peripheral development to the transcriptional regulators involved in their tissue residency program. In addition, we discuss the distinct signalling pathways that engage the inflammatory adaptation of tissue-resident TREG cells, and how they relate to their ability to recognize tissue and pathogen-derived danger signals.

Interleukin-2 signaling in the regulation of T cell biology in autoimmunity and cancer

Interleukin-2 (IL-2) is a critical cytokine for T cell peripheral tolerance and immunity. Here, we review how IL-2 interaction with the high-affinity IL-2 receptor (IL-2R) supports the development and homeostasis of regulatory T cells and contributes to the differentiation of helper, cytotoxic, and memory T cells. A critical element for each T cell population is the expression of CD25 (Il2rα), which heightens the receptor affinity for IL-2. Signaling through the high-affinity IL-2R also reinvigorates CD8+ exhausted T (Tex) cells in response to checkpoint blockade. We consider the molecular underpinnings reflecting how IL-2R signaling impacts these various T cell subsets and the implications for enhancing IL-2-dependent immunotherapy of autoimmunity, other inflammatory disorders, and cancer.

Rosa roxburghii Tratt juice inhibits NF-κB and increases IL-2 to alleviates the Foxp3-mediated Tregs imbalance in the peripheral blood of arseniasis patients

Arsenic can cause immune inflammation, which is the basis of arsenic-induced damage to multiple organs and systems. Forkhead box P3 (Foxp3)-labelled CD4+CD25+ regulatory T cells (Tregs) play an essential role in maintaining immune homeostasis. Nuclear factor-κb (NF-κB) and Interleukin-2 (IL-2) are critical regulators of Foxp3. Rosa roxburghii Tratt (RRT) is an edible medicinal plant with anti-inflammation effects. In this study, a control group (n = 41) and an arseniasis group (n = 209) were recruited, and screened subjects from the arseniasis patients for RRTJ (n = 46) or placebo (n = 43) to explore the possible mechanism by which RRT alleviates immune inflammation. The results indicated that RRTJ can inhibits NF-κB and increases IL-2, and alleviates the Foxp3-mediated Tregs imbalance in the peripheral blood of arseniasis patients. In summary, these findings suggest a novel intervention or therapeutic target for immune inflammation in arseniasis patients and provide new evidence that RRTJ inhibits immune inflammation.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-023-01384-0.

The Role of Regulatory T Cells in Allergic Diseases: Collegium Internationale Allergologicum (CIA) Update 2024

BACKGROUND

Allergy represents a major health problem of increasing prevalence worldwide with a high socioeconomic impact. Our knowledge on the molecular mechanisms underlying allergic diseases and their treatments has significantly improved over the last years. The generation of allergen-specific regulatory T cells (Tregs) is crucial in the induction of healthy immune responses to allergens, preventing the development and worsening of allergic diseases.

SUMMARY

In the last decades, intensive research has focused on the study of the molecular mechanisms involved in Treg development and Treg-mediated suppression. These mechanisms are essential for the induction of sustained tolerance by allergen-specific immunotherapy (AIT) after treatment discontinuation. Compelling experimental evidence demonstrated altered suppressive capacity of Tregs in patients suffering from allergic rhinitis, allergic asthma, food allergy, or atopic dermatitis, as well as the restoration of their numbers and functionality after successful AIT.

KEY MESSAGE

The better understanding of the molecular mechanisms involved in Treg generation during allergen tolerance induction might well contribute to the development of novel strategies for the prevention and treatment of allergic diseases.

Paclitaxel combined with Compound K inducing pyroptosis of non-small cell lung cancer cells by regulating Treg/Th17 balance

BACKGROUND

Immune checkpoint inhibitors, which have attracted much attention in recent years, have achieved good efficacy, but their use is limited by the high incidence of acquired drug resistance. Therefore, there is an urgent need to develop new immunotherapy drugs. Compound taxus chinensis capsule (CTC) is an oral paclitaxel compound drug, clinical results showed it can change the number of regulatory T cells and T helper cell 17 in peripheral blood. Regulating the balance between regulatory T cells and T helper cell 17 is considered to be an effective anticancer strategy. Paclitaxel and ginsenoside metabolite compound K are the main immunomodulatory components, it is not clear that paclitaxel combined with compound K can inhibit tumor development by regulating the balance between regulatory T cell and T helper cell 17.

METHODS

MTT, EdU proliferation and plate colony formation assay were used to determine the concentration of paclitaxel and compound K. AnnexinV-FITC/PI staining, ELISA, Western Blot assay, Flow Cytometry and Immunofluorescence were used to investigate the effect of paclitaxel combined with compound K on Lewis cell cultured alone or co-cultured with splenic lymphocyte. Finally, transplanted tumor C57BL/6 mice model was constructed to investigate the anti-cancer effect in vivo.

RESULTS

According to the results of MTT, EdU proliferation and plate colony formation assay, paclitaxel (10 nM) and compound K (60 μM) was used to explore the mechanism. The results of Flow Cytometry demonstrated that paclitaxel combined with compound K increased the number of T helper cell 17 and decreased the number of regulatory T cells, which induced pyroptosis of cancer cells. The balance was mediated by the JAK-STAT pathway according to the results of Western Blot and Immunofluorescence. Finally, the in vivo results showed that paclitaxel combined with compound K significantly inhibit the progression of lung cancer.

CONCLUSIONS

In this study, we found that paclitaxel combined with compound K can activate CD8+ T cells and induce pyroptosis of tumor cells by regulating the balance between regulatory T cells and T helper cell 17. These results demonstrated that this is a feasible treatment strategy for lung cancer.

Immunoswitch Nanomodulators Enable Active Targeting and Selective Proliferation of Regulatory T Cells for Multiple Sclerosis Therapy

Interleukin-2 (IL-2) used in multiple sclerosis (MS) therapy modulates the balance between regulatory T (Treg) cells and effector T (Teff) cells. However, the off-target activation of Teff cells by IL-2 limits its clinical application. Therefore, a rapidly prepared immunoswitch nanomodulator termed aT-IL2C NPs was developed, which specifically recognized Treg cells with high TIGIT expression thanks to the presence of an anti-TIGIT and an IL-2/JES6-1 complex (IL2C) being delivered to Treg cells but not to Teff cells with low TIGIT expression. Then, IL2C released IL-2 due to the specific expression of the high-affinity IL-2 receptor on Treg cells, thus enabling the active targeting and selective proliferation of Treg cells. Moreover, the anti-TIGIT of aT-IL2C NPs selectively inhibited the proliferation of Teff cells while leaving the proliferation of Treg cells unaffected. In addition, since the IL-2 receptor on Teff cells had medium-affinity, the IL2C hardly released IL-2 to Teff cells, thus enabling the inhibition of Teff cell proliferation. The treatment of experimental autoimmune encephalomyelitis (EAE) mice with aT-IL2C NPs ameliorated the severity of the EAE and restored white matter integrity. Collectively, this work described a potential promising agent for effective MS therapy.

Regulatory T cells in skin mediate immune privilege of the hair follicle stem cell niche

Immune tolerance is maintained in lymphoid organs (LOs). Despite the presence of complex immune cell networks in non-LOs, it is unknown whether self-tolerance is maintained in these tissues. We developed a technique to restrict genetic recombination to regulatory T cells (Tregs) only in skin. Selective depletion of skin Tregs resulted in T cell-mediated inflammation of hair follicles (HFs). Suppression did not rely on CTLA-4, but instead on high-affinity interleukin-2 (IL-2) receptor expression by skin Tregs, functioning exclusively in a cell-extrinsic manner. In a novel model of HF stem cell (HFSC)-driven autoimmunity, we reveal that skin Tregs immunologically protect the HFSC niche. Finally, we used spatial transcriptomics to identify aberrant IL-2 signaling at stromal-HF interfaces in a rare form of human alopecia characterized by HFSC destruction and alopecia areata. Collectively, these results reveal the fundamental biology of Tregs in skin uncoupled from the systemic pool and elucidate a mechanism of self-tolerance.

Regulatory T Cells for Control of Autoimmunity

Regulatory T (Treg) cells, which specifically express the master transcription factor FoxP3, are indispensable for the maintenance of immunological self-tolerance and homeostasis. Their functional or numerical anomalies can be causative of autoimmune and other inflammatory diseases. Recent advances in the research of the cellular and molecular basis of how Treg cells develop, exert suppression, and maintain their function have enabled devising various ways for controlling physiological and pathological immune responses by targeting Treg cells. It is now envisaged that Treg cells as a "living drug" are able to achieve antigen-specific immune suppression of various immune responses and reestablish immunological self-tolerance in the clinic.

Distinct use of super-enhancer elements controls cell type-specific CD25 transcription and function

The IL-2 receptor α chain (IL-2Rα/CD25) is constitutively expressed on double-negative (DN2/DN3 thymocytes and regulatory T cells (Tregs) but induced by IL-2 on T and natural killer (NK) cells, with Il2ra expression regulated by a STAT5-dependent super-enhancer. We investigated CD25 regulation and function using a series of mice with deletions spanning STAT5-binding elements. Deleting the upstream super-enhancer region mainly affected constitutive CD25 expression on DN2/DN3 thymocytes and Tregs, with these mice developing autoimmune alopecia, whereas deleting an intronic region decreased IL-2-induced CD25 on peripheral T and NK cells. Thus, distinct super-enhancer elements preferentially control constitutive versus inducible expression in a cell type-specific manner. The mediator-1 coactivator colocalized with specific STAT5-binding sites. Moreover, both upstream and intronic regions had extensive chromatin interactions, and deletion of either region altered the super-enhancer structure in mature T cells. These results demonstrate differential functions for distinct super-enhancer elements, thereby indicating previously unknown ways to manipulate CD25 expression in a cell type-specific fashion.

Treg cell: Critical role of regulatory T-cells in depression

Depression is a highly prevalent disorder of the central nervous system. The neuropsychiatric symptoms of clinical depression are persistent and include fatigue, anorexia, weight loss, altered sleep patterns, hyperalgesia, melancholia, anxiety, and impaired social behaviours. Mounting evidences suggest that neuroinflammation triggers dysregulated cellular immunity and increases susceptibility to psychiatric diseases. Neuroimmune responses have transformed the clinical approach to depression because of their roles in its pathophysiology and their therapeutic potential. In particular, activated regulatory T (Treg) cells play an increasingly evident role in the inflammatory immune response. In this review, we summarized the available data and discussed in depth the fundamental roles of Tregs in the pathogenesis of depression, as well as the clinical therapeutic potential of Tregs. We aimed to provide recent information regarding the potential of Tregs as immune-modulating biologics for the treatment and prevention of long-term neuropsychiatric symptoms of depression.

T cells in health and disease

T cells are crucial for immune functions to maintain health and prevent disease. T cell development occurs in a stepwise process in the thymus and mainly generates CD4⁺ and CD8⁺ T cell subsets. Upon antigen stimulation, naïve T cells differentiate into CD4⁺ helper and CD8⁺ cytotoxic effector and memory cells, mediating direct killing, diverse immune regulatory function, and long-term protection. In response to acute and chronic infections and tumors, T cells adopt distinct differentiation trajectories and develop into a range of heterogeneous populations with various phenotype, differentiation potential, and functionality under precise and elaborate regulations of transcriptional and epigenetic programs. Abnormal T-cell immunity can initiate and promote the pathogenesis of autoimmune diseases. In this review, we summarize the current understanding of T cell development, CD4⁺ and CD8⁺ T cell classification, and differentiation in physiological settings. We further elaborate the heterogeneity, differentiation, functionality, and regulation network of CD4⁺ and CD8⁺ T cells in infectious disease, chronic infection and tumor, and autoimmune disease, highlighting the exhausted CD8⁺ T cell differentiation trajectory, CD4⁺ T cell helper function, T cell contributions to immunotherapy and autoimmune pathogenesis. We also discuss the development and function of γδ T cells in tissue surveillance, infection, and tumor immunity. Finally, we summarized current T-cell-based immunotherapies in both cancer and autoimmune diseases, with an emphasis on their clinical applications. A better understanding of T cell immunity provides insight into developing novel prophylactic and therapeutic strategies in human diseases.

Presentation of Human Neural Stem Cell Antigens Drives Regulatory T Cell Induction

Transplantation of human neural stem cells (hNSCs) is a promising regenerative therapy to promote remyelination in patients with multiple sclerosis (MS). Transplantation of hNSCs has been shown to increase the number of CD4+CD25+Foxp3+ T regulatory cells (Tregs) in the spinal cords of murine models of MS, which is correlated with a strong localized remyelination response. However, the mechanisms by which hNSC transplantation leads to an increase in Tregs in the CNS remains unclear. We report that hNSCs drive the conversion of T conventional (Tconv) cells into Tregs in vitro. Conversion of Tconv cells is Ag driven and fails to occur in the absence of TCR stimulation by cognate antigenic self-peptides. Furthermore, CNS Ags are sufficient to drive this conversion in the absence of hNSCs in vitro and in vivo. Importantly, only Ags presented in the thymus during T cell selection drive this Treg response. In this study, we investigate the mechanisms by which hNSC Ags drive the conversion of Tconv cells into Tregs and may provide key insight needed for the development of MS therapies.

The Role of Regulatory T Cells in the Onset and Progression of Primary Sjögren's Syndrome

Regulatory T cells (Tregs) play a key role in maintaining immune balance and regulating the loss of self-tolerance mechanisms in various autoimmune diseases, including primary Sjögren's syndrome (pSS). With the development of pSS primarily in the exocrine glands, lymphocytic infiltration occurs in the early stages, mainly due to activated CD4⁺ T cells. Subsequently, in the absence of rational therapy, patients develop ectopic lymphoid structures and lymphomas. While the suppression of autoactivated CD4⁺ T cells is involved in the pathological process, the main role belongs to Tregs, making them a target for research and possible regenerative therapy. However, the available information about their role in the onset and progression of this disease seems unsystematized and, in certain aspects, controversial. In our review, we aimed to organize the data on the role of Tregs in the pathogenesis of pSS, as well as to discuss possible strategies of cell therapy for this disease. This review provides information on the differentiation, activation, and suppressive functions of Tregs and the role of the FoxP3 protein in these processes. It also highlights data on various subpopulations of Tregs in pSS, their proportion in the peripheral blood and minor salivary glands of patients as well as their role in the development of ectopic lymphoid structures. Our data emphasize the need for further research on Tregs and highlight their potential use as a cell-based therapy.

Genomic Analysis of Foxp3 Function in Regulatory T Cells

Regulatory T (Treg) cells are critical for tolerance to self-antigens and for preventing autoimmunity. Foxp3 has been identified as a Treg cell lineage-defining transcription factor controlling Treg cell differentiation and function. In this article, we review the current mechanistic and systemic understanding of Foxp3 function enabled by experimental and computational advances in high-throughput genomics.

Significance of regulatory T cells in cancer immunology and immunotherapy

Immunosuppression in the tumour microenvironment (TME) attenuates antitumor immunity, consequently hindering protective immunosurveillance and preventing effective antitumor immunity induced by cancer immunotherapy. Multiple mechanisms including immune checkpoint molecules, such as CTLA-4, PD-1, and LAG-3, and immunosuppressive cells are involved in the immunosuppression in the TME. Regulatory T (Treg) cells, a population of immunosuppressive cells, play an important role in inhibiting antitumor immunity. Therefore, Treg cells in the TME correlate with an unfavourable prognosis in various cancer types. Thus, Treg cell is considered to become a promising target for cancer immunotherapy. Elucidating Treg cell functions in cancer patients is therefore crucial for developing optimal Treg cell-targeted immunotherapy. Here, we describe Treg cell functions and phenotypes in the TME from the perspective of Treg cell-targeted immunotherapy.

Human FOXP3 and tumour microenvironment

The tumour microenvironment (TME) is a complex system composed of cancer cells, stromal cells and immune cells. Regulatory T cells (Tregs) in the TME impede immune surveillance of tumours and suppress antitumor immune responses. Transcription factor forkhead box protein 3 (FOXP3) is the main marker of Tregs, which dominates the function of Tregs. FOXP3 was originally thought to be a Tregs-specific expression molecule, and recent studies have found that FOXP3 is expressed in a variety of tumours with inconsistent functional roles. This review summarizes the recent progress of infiltrating Treg-FOXP3 and tumour-FOXP3 in TME, discusses the communication mechanism between FOXP3⁺ cells and effector T cells in TME, the relationship between FOXP3 and clinical prognosis, and the potential of FOXP3-targeted therapy.

Research advances on targeted-Treg therapies on immune-mediated kidney diseases

The primary function of regulatory T cells (Tregs) is blocking the pathogenic immunological response mediated by autoreactive cells, establishing and maintaining immune homeostasis in tissues. Kidney diseases are often caused by Immune imbalance, including alloimmune graft damage after renal transplantation, direct immune-mediated kidney diseases like membranous nephropathy (MN) and anti-glomerular basement membrane (anti-GBM) glomerulonephritis, as well as indirect immune-mediated ones like Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAVs), IgA nephropathy (IgAN) and lupus nephritis (LN). Treg cells are deficient numerically and/or functionally in those kidney diseases. Targeted-Treg therapies, including adoptive Tregs transfer therapy and low-dose IL-2 therapy, have begun to thrive in treating autoimmune diseases in recent years. However, the clinical use of targeted Treg-therapies is rarely mentioned in those kidney diseases above except for kidney transplantation. This article mainly discusses the newest progressions of targeted-Treg therapies in those specific examples of immune-mediated kidney diseases. Meanwhile, we also reviewed the main factors that affect Treg development and differentiation, hoping to inspire new strategies to develop target Tregs-therapies. Lastly, we emphasize the significant impediments and prospects to the clinical translation of target-Treg therapy. We advocate for more preclinical and clinical studies on target Tregs-therapies to decipher Tregs in those diseases.

Comprehensive analysis of a novel RNA modifications-related model in the prognostic characterization, immune landscape and drug therapy of bladder cancer

Background: Bladder cancer (BCa) is the leading reason for death among genitourinary malignancies. RNA modifications in tumors closely link to the immune microenvironment. Our study aimed to propose a promising model associated with the "writer" enzymes of five primary RNA adenosine modifications (including m⁶A, m⁶A_m, m¹A, APA, and A-to-I editing), thus characterizing the clinical outcome, immune landscape and therapeutic efficacy of BCa. Methods: Unsupervised clustering was employed to categorize BCa into different RNA modification patterns based on gene expression profiles of 34 RNA modification "writers". The RNA modification "writers" score (RMS) signature composed of RNA phenotype-associated differentially expressed genes (DEGs) was established using the least absolute shrinkage and selection operator (LASSO), which was evaluated in meta-GEO (including eight independent GEO datasets) training cohort and the TCGA-BLCA validation cohort. The hub genes in the RMS model were determined via weighted gene co-expression network analysis (WGCNA) and were further validated using human specimen. The potential applicability of the RMS model in predicting the therapeutic responsiveness was assessed through the Genomics of Drug Sensitivity in Cancer database and multiple immunotherapy datasets. Results: Two distinct RNA modification patterns were determined among 1,410 BCa samples from a meta-GEO cohort, showing radically varying clinical outcomes and biological characteristics. The RMS model comprising 14 RNA modification phenotype-associated prognostic DEGs positively correlated with the unsatisfactory outcome of BCa patients in meta-GEO training cohort (HR = 3.00, 95% CI = 2.19-4.12) and TCGA-BLCA validation cohort (HR = 1.53, 95% CI = 1.13-2.09). The infiltration of immunosuppressive cells and the activation of EMT, angiogenesis, IL-6/JAK/STAT3 signaling were markedly enriched in RMS-high group. A nomogram exhibited high prognostic prediction accuracy, with a concordance index of 0.785. The therapeutic effect of chemotherapeutic agents and antibody-drug conjugates was significantly different between RMS-low and -high groups. The combination of the RMS model and conventional characteristics (TMB, TNB and PD-L1) achieved an optimal AUC value of 0.828 in differentiating responders from non-responders to immunotherapy. Conclusion: We conferred the first landscape of five forms of RNA modifications in BCa and emphasized the excellent power of an RNA modifications-related model in evaluating BCa prognosis and immune landscape.

Selenoprotein I deficiency in T cells promotes differentiation into tolerant phenotypes while decreasing Th17 pathology

Selenoprotein I (SELENOI) is an ethanolamine phospholipid transferase contributing to cellular metabolism and the synthesis of glycosylphosphatidylinositol (GPI) anchors. SELENOI knockout (KO) in T cells has been shown to impair metabolic reprogramming during T cell activation and reduce GPI-anchored Thy-1 levels, which are both crucial for Th17 differentiation. This suggests SELENOI may be important for Th17 differentiation, and we found that SELENOI was indeed up-regulated early during the activation of naïve CD4+ T cells in Th17 conditions. SELENOI KO reduced RORγt mRNA levels by decreasing SOX5 and STAT3 binding to promoter and enhancer regions in the RORC gene encoding this master regulator of Th17 cell differentiation. Differentiation of naïve CD4+ T cells into inflammatory versus tolerogenic Th cell subsets was analyzed and results showed that SELENOI deficiency skewed differentiation away from pathogenic Th17 cells (RORγt+ and IL-17A+ ) while promoting tolerogenic phenotypes (Foxp3+ and IL-10+ ). Wild-type and T cell-specific SELENOI KO mice were subjected to experimental autoimmune encephalitis (EAE), with KO mice exhibiting diminished clinical symptoms, reduced CNS pathology and decreased T cell infiltration. Flow cytometry showed that SELENOI T cell KO mice exhibited lower CD4+ RORγt+ and CD4+ IL-17A+ T cells and higher CD4+ CD25+ FoxP3+ T cells in CNS tissues of mice subjected to EAE. Thus, the metabolic enzyme SELENOI is up-regulated to promote RORγt transcription that drives Th17 differentiation, and SELENOI deficiency shifts differentiation toward tolerogenic phenotypes while protecting against pathogenic Th17 responses.

CTLA-4 on thymic epithelial cells complements Aire for T cell central tolerance

Medullary thymic epithelial cells (mTECs) are essential for the establishment of T cell central tolerance. The transcription factor Aire plays a key role in this process, but other factors remain understudied. We found that a small population of mTECs expressed the coinhibitory receptor cytotoxic T lymphocyte-associated protein 4 (CTLA-4). These CTLA-4⁺ cells were detectable in perinates, peaked around young adulthood and expanded sixfold in the absence of Aire. Single-cell transcriptomics revealed CTLA-4⁺ mTECs to express a distinct gene signature encoding molecules associated with antigen presentation and interferon-gamma signaling. Mice conditionally lacking CTLA-4 in thymic epithelial cells had no major immunological deficiencies but displayed a mildly increased inflammatory tone and a partial defect in the generation of Foxp3⁺CD4⁺ regulatory T cells. Consequently, these mice developed modest levels of autoantibodies and lymphocytic infiltration of peripheral tissues. Thus, CTLA-4 expression in mTECs complements Aire to establish T cell central tolerance.

Pleiotropic effects of antibiotics on T cell metabolism and T cell-mediated immunity

T cells orchestrate adaptive and innate immune responses against pathogens and transformed cells. However, T cells are also the main adaptive effector cells that mediate allergic and autoimmune reactions. Within the last few years, it has become abundantly clear that activation, differentiation, effector function, and environmental adaptation of T cells is closely linked to their energy metabolism. Beyond the provision of energy equivalents, metabolic pathways in T cells generate building blocks required for clonal expansion. Furthermore, metabolic intermediates directly serve as a source for epigenetic gene regulation by histone and DNA modification mechanisms. To date, several antibiotics were demonstrated to modulate the metabolism of T cells especially by altering mitochondrial function. Here, we set out to systematically review current evidence about how beta-lactam antibiotics, macrolides, fluoroquinolones, tetracyclines, oxazolidinones, nitroimidazoles, and amphenicols alter the metabolism and effector functions of CD4+ T helper cell populations and CD8+ T cells in vitro and in vivo. Based on this evidence, we have developed an overview on how the use of these antibiotics may be beneficial or detrimental in T cell-mediated physiological and pathogenic immune responses, such as allergic and autoimmune diseases, by altering the metabolism of different T cell populations.

Opposing functions of circadian protein DBP and atypical E2F family E2F8 in anti-tumor Th9 cell differentiation

Interleukin-9 (IL-9)-producing CD4⁺ T helper cells (Th9) have been implicated in allergy/asthma and anti-tumor immunity, yet molecular insights on their differentiation from activated T cells, driven by IL-4 and transforming growth factor-beta (TGF-β), is still lacking. Here we show opposing functions of two transcription factors, D-binding protein (DBP) and E2F8, in controlling Th9 differentiation. Specifically, TGF-β and IL-4 signaling induces phosphorylation of the serine 213 site in the linker region of the Smad3 (pSmad3L-Ser²¹³) via phosphorylated p38, which is necessary and sufficient for Il9 gene transcription. We identify DBP and E2F8 as an activator and repressor, respectively, for Il9 transcription by pSmad3L-Ser²¹³. Notably, Th9 cells with siRNA-mediated knockdown for Dbp or E2f8 promote and suppress tumor growth, respectively, in mouse tumor models. Importantly, DBP and E2F8 also exhibit opposing functions in regulating human TH9 differentiation in vitro. Thus, our data uncover a molecular mechanism of Smad3 linker region-mediated, opposing functions of DBP and E2F8 in Th9 differentiation.

Engineering IL-2 for immunotherapy of autoimmunity and cancer

Preclinical studies of the T cell growth factor activity of IL-2 resulted in this cytokine becoming the first immunotherapy to be approved nearly 30 years ago by the US Food and Drug Administration for the treatment of cancer. Since then, we have learnt the important role of IL-2 in regulating tolerance through regulatory T cells (Treg cells) besides promoting immunity through its action on effector T cells and memory T cells. Another pivotal event in the history of IL-2 research was solving the crystal structure of IL-2 bound to its tripartite receptor, which spurred the development of cell type-selective engineered IL-2 products. These new IL-2 analogues target Treg cells to counteract the dysregulated immune system in the context of autoimmunity and inflammatory disorders or target effector T cells, memory T cells and natural killer cells to enhance their antitumour responses. IL-2 biologics have proven to be effective in preclinical studies and clinical assessment of some is now underway. These studies will soon reveal whether engineered IL-2 biologics are truly capable of harnessing the IL-2-IL-2 receptor pathway as effective monotherapies or combination therapies for autoimmunity and cancer.

DNA Methylation in Regulatory T Cell Differentiation and Function: Challenges and Opportunities

As a bona fide epigenetic marker, DNA methylation has been linked to the differentiation and function of regulatory T (Treg) cells, a subset of CD4 T cells that play an essential role in maintaining immune homeostasis and suppressing autoimmunity and antitumor immune response. DNA methylation undergoes dynamic regulation involving maintenance of preexisting patterns, passive and active demethylation, and de novo methylation. Scattered evidence suggests that these processes control different stages of Treg cell lifespan ranging from lineage induction to cell fate maintenance, suppression of effector T cells and innate immune cells, and transdifferentiation. Despite significant progress, it remains to be fully explored how differential DNA methylation regulates Treg cell fate and immunological function. Here, we review recent progress and discuss the questions and challenges for further understanding the immunological roles and mechanisms of dynamic DNA methylation in controlling Treg cell differentiation and function. We also explore the opportunities that these processes offer to manipulate Treg cell suppressive function for therapeutic purposes by targeting DNA methylation.

IL-2 and IL-15 drive intrathymic development of distinct periphery-seeding CD4+Foxp3+ regulatory T lymphocytes

Development of Foxp3-expressing regulatory T-lymphocytes (Treg) in the thymus is controlled by signals delivered in T-cell precursors via the TCR, co-stimulatory receptors, and cytokine receptors. In absence of IL-2, IL-15 or their receptors, fewer Treg apparently develop in the thymus. However, it was recently shown that a substantial part of thymic Treg are cells that had recirculated from the periphery back to the thymus, troubling interpretation of these results. We therefore reassessed the involvement of IL-2 and IL-15 in the development of Treg, taking into account Treg-recirculation. At the age of three weeks, when in wt and IL-15-deficient (but not in IL-2-deficient) mice substantial amounts of recirculating Treg are present in the thymus, we found similarly reduced proportions of newly developed Treg in absence of IL-2 or IL-15, and in absence of both cytokines even less Treg developed. In neonates, when practically no recirculating Treg were found in the thymus, the absence of IL-2 led to substantially more reduced Treg-development than deficiency in IL-15. IL-2 but not IL-15 modulated the CD25, GITR, OX40, and CD73-phenotypes of the thymus-egress-competent and periphery-seeding Treg-population. Interestingly, IL-2 and IL-15 also modulated the TCR-repertoire expressed by developing Treg. Upon transfer into Treg-less Foxp3^sf mice, newly developed Treg from IL-2- (and to a much lesser extent IL-15-) deficient mice suppressed immunopathology less efficiently than wt Treg. Taken together, our results firmly establish important non-redundant quantitative and qualitative roles for IL-2 and, to a lesser extent, IL-15 in intrathymic Treg-development.

Improvement of the sepsis survival rate by adenosine 2a receptor antagonists depends on immune regulatory functions of regulatory T-cells

Adenosine shows a significant immunosuppressive effect in sepsis via binding to the adenosine 2a receptor (A2aR). Both genetic deletion and pharmacological inhibition of the A2aR may improve survival in sepsis. However, available research on this protective mechanism is quite limited. We used an A2aR antagonist (ZM241385) to treat a cecal ligation and puncture model of normal mice or regulatory T-cell (Treg)-depletion mice and found that the protective effect of ZM241385 is dependent on Tregs. Mechanically, A2aR inactivation was associated with decreased frequencies and reduced function of Foxp3+ Tregs, as evidenced by Foxp3 and CTLA-4 expression and classical effector T-cell proliferative assays, suggesting Treg modulation is a potential protective mechanism against sepsis. Simultaneously, the function and quantity of abdominal neutrophils were improved with ZM241385 treatment. To see if a link exists between them, Tregs and neutrophils were co-cultured, and it was found that ZM241385 blocked the inhibitory effect of Tregs on neutrophils. According to our research, Tregs play a key role in how A2aR antagonists improve sepsis prognosis and bacterial clearance.

Suppression of FOXP3 expression by the AP-1 family transcription factor BATF3 requires partnering with IRF4

FOXP3 is the lineage-defining transcription factor for Tregs, a cell type critical to immune tolerance, but the mechanisms that control FOXP3 expression in Tregs remain incompletely defined, particularly as it relates to signals downstream of TCR and CD28 signaling. Herein, we studied the role of IRF4 and BATF3, two transcription factors upregulated upon T cell activation, to the conversion of conventional CD4+ T cells to FOXP3+ T cells (iTregs) in vitro. We found that IRF4 must partner with BATF3 to bind to a regulatory region in the Foxp3 locus where they cooperatively repress FOXP3 expression and iTreg induction. In addition, we found that interactions of these transcription factors are necessary for glycolytic reprogramming of activated T cells that is antagonistic to FOXP3 expression and stability. As a result, Irf4 KO iTregs show increased demethylation of the critical CNS2 region in the Foxp3 locus. Together, our findings provide important insights how BATF3 and IRF4 interactions integrate activating signals to control CD4+ cell fate decisions and govern Foxp3 expression.

Nature vs. nurture: FOXP3, genetics, and tissue environment shape Treg function

The importance of regulatory T cells (Tregs) in preventing autoimmunity has been well established; however, the precise alterations in Treg function in autoimmune individuals and how underlying genetic associations impact the development and function of Tregs is still not well understood. Polygenetic susceptibly is a key driving factor in the development of autoimmunity, and many of the pathways implicated in genetic association studies point to a potential alteration or defect in regulatory T cell function. In this review transcriptomic control of Treg development and function is highlighted with a focus on how these pathways are altered during autoimmunity. In combination, observations from autoimmune mouse models and human patients now provide insights into epigenetic control of Treg function and stability. How tissue microenvironment influences Treg function, lineage stability, and functional plasticity is also explored. In conclusion, the current efficacy and future direction of Treg-based therapies for Type 1 Diabetes and other autoimmune diseases is discussed. In total, this review examines Treg function with focuses on genetic, epigenetic, and environmental mechanisms and how Treg functions are altered within the context of autoimmunity.

Role of CNSs Conserved Distal Cis-Regulatory Elements in CD4 + T Cell Development and Differentiation

Naïve CD4⁺ T cells differentiate into diverse subsets of effector cells and perform various homeostatic and immune functions. The differentiation and maintenance of these different subsets are controlled through the upregulation and silencing of master genes. Mechanistic studies of the regulation of these master genes identified conserved and distal intronic regulatory elements, which are accessible subsets of conserved non-coding sequences (CNSs), acting as cis-regulatory elements in a lineage-specific manner that controls the function of CD4⁺ T cells. Abnormal CNS activity is associated with incorrect expression of master genes and development of autoimmune diseases or immune suppression. Here, we describe the function of several conserved, distal cis-regulatory elements at the Foxp3, Rorc, Il-4, Il-10 and Il-17 gene locus were shown to play important roles in CD4⁺ T cells differentiation. Together, this review briefly outlines currently known CNSs, with a focus on their regulations and functions in complexes modulating the differentiation and maintenance of various CD4⁺ T cells subsets, in health and disease contexts, as well as during the conversion of T regulatory cells to T helper 17 cells. This article will provide a comprehensive view of CNSs conserved distal cis-regulatory elements at a few loci that control aspects of CD4⁺ T cells function.

In Search for the Missing Link in APECED-like Conditions: Analysis of the AIRE Gene in a Series of 48 Patients

Autoimmune diseases are a heterogeneous group of disorders of the immune system. They can cluster in the same individual, revealing various preferential associations for polyendocrine autoimmune syndromes. Clinical observation, together with advances in genetics and the understanding of pathophysiological processes, has further highlighted that autoimmunity can be associated with immunodeficiency; autoimmunity may even be the first primary immunodeficiency manifestation. Analysis of susceptibility genes for the development of these complex phenotypes is a fundamental issue. In this manuscript, we revised the clinical and immunologic features and the presence of AIRE gene variations in a cohort of 48 patients affected by high polyautoimmunity complexity, i.e., APECED-like conditions, also including patients affected by primary immunodeficiency. Our results evidenced a significant association of the S278R polymorphism of the AIRE gene with APECED-like conditions, including both patients affected by autoimmunity and immunodeficiency and patients with polyautoimmunity compared to healthy controls. A trend of association was also observed with the IVS9+6 G>A polymorphism. The results of this genetic analysis emphasize the need to look for additional genetic determinants playing in concert with AIRE polymorphisms. This will help to improve the diagnostic workup and ensure a precision medicine approach to targeted therapies in APECED-like patients.

Instructive Cues of Thymic T Cell Selection

A high diversity of αβ T cell receptors (TCRs), capable of recognizing virtually any pathogen but also self-antigens, is generated during T cell development in the thymus. Nevertheless, a strict developmental program supports the selection of a self-tolerant T cell repertoire capable of responding to foreign antigens. The steps of T cell selection are controlled by cortical and medullary stromal niches, mainly composed of thymic epithelial cells and dendritic cells. The integration of important cues provided by these specialized niches, including (a) the TCR signal strength induced by the recognition of self-peptide-MHC complexes, (b) costimulatory signals, and (c) cytokine signals, critically controls T cell repertoire selection. This review discusses our current understanding of the signals that coordinate positive selection, negative selection, and agonist selection of Foxp3⁺ regulatory T cells. It also highlights recent advances that have unraveled the functional diversity of thymic antigen-presenting cell subsets implicated in T cell selection.

Role of Cytokines in Thymic Regulatory T Cell Generation: Overview and Updates

CD4⁺CD25⁺Foxp3⁺ Regulatory (Treg) T cells are mainly generated within the thymus. However, the mechanism of thymic Treg cell (tTreg cell) generation remains to be fully revealed. Although the functions of TCR/CD28 co-stimulation have been widely accepted, the functions of cytokines in the generation of tTreg cells remain highly controversial. In this review, we summarize the existing studies on cytokine regulation of tTreg cell generation. By integrating the key findings of cytokines in tTreg cell generation, we have concluded that four members of γc family cytokines (IL-2, IL-4, IL-7 and IL-15), transforming growth factor β (TGF-β), and three members of TNF superfamily cytokines (GITRL, OX40L and TNF-α) play vitally important roles in regulating tTreg cell generation. We also point out all disputed points and highlight critical scientific questions that need to be addressed in the future.

Bone Morphogenetic Proteins Shape Treg Cells

The transforming growth factor-β (TGF-β) family includes cytokines controlling cell behavior, differentiation and homeostasis of various tissues including components of the immune system. Despite well recognized importance of TGF-β in controlling T cell functions, the immunomodulatory roles of many other members of the TGF-β cytokine family, especially bone morphogenetic proteins (BMPs), start to emerge. Bone Morphogenic Protein Receptor 1α (BMPR1α) is upregulated by activated effector and Foxp3+ regulatory CD4+ T cells (Treg cells) and modulates functions of both of these cell types. BMPR1α inhibits generation of proinflammatory Th17 cells and sustains peripheral Treg cells. This finding underscores the importance of the BMPs in controlling Treg cell plasticity and transition between Treg and Th cells. BMPR1α deficiency in in vitro induced and peripheral Treg cells led to upregulation of Kdm6b (Jmjd3) demethylase, an antagonist of polycomb repressive complex 2 (PRC2), and cell cycle inhibitor Cdkn1a (p21Cip1) promoting cell senescence. This indicates that BMPs and BMPR1α may represent regulatory modules shaping epigenetic landscape and controlling proinflammatory reprogramming of Th and Treg cells. Revealing functions of other BMP receptors and their crosstalk with receptors for TGF-β will contribute to our understanding of peripheral immunoregulation.

The activation of PPARγ enhances Treg responses through up-regulating CD36/CPT1-mediated fatty acid oxidation and subsequent N-glycan branching of TβRII/IL-2Rα

BACKGROUND

Peroxisome proliferator-activated receptor gamma (PPARγ) is an enhancer of Treg responses, but the mechanisms remain elusive. This study aimed to solve this problem in view of cellular metabolism.

METHODS

Three recognized PPARγ agonists (synthetic agonist: rosiglitazone; endogenous ligand: 15d-PGJ2; natural product: morin) were used as the tools to activate PPARγ. The fatty acid oxidation (FAO) was evaluated through the detection of fatty acid uptake, oxygen consumption rate, mitochondrial mass, mitochondrial membrane potential and acetyl-CoA level. The involvement of UDP-GlcNAc/N-linked glycosylation axis and the exact role of PPARγ in the action of PPARγ agonists were determined by flow cytometry, Q-PCR, western blotting, a commercial kit for enzyme activity and CRISPR/Cas9-mediated knockout.

RESULTS

Rosiglitazone, 15d-PGJ2 and morin all increased the frequency of CD4⁺Foxp3⁺ Treg cells generated from naïve CD4⁺ T cells, boosted the transcription of Foxp3, IL-10, CTLA4 and TIGIT, and facilitated the function of Treg cells. They significantly promoted FAO in differentiating Treg cells by up-regulating the levels of CD36 and CPT1 but not other enzymes involved in FAO such as ACADL, ACADM, HADHA or HADHB, and siCD36 or siCPT1 dampened PPARγ agonists-promoted Treg responses. Moreover, PPARγ agonists enhanced UDP-GlcNAc biosynthesis and subsequent N-linked glycosylation, but did not affect the expressions of N-glycan branching enzymes Mgat1, 2, 4 and 5. Notably, the enzyme activity of phosphofructokinase (PFK) was inhibited by PPARγ agonists and the effect was limited by siCD36 or siCPT1, implying PFK to be a link between PPARγ agonists-promoted FAO and UDP-GlcNAc biosynthesis aside from acetyl-CoA. Furthermore, PPARγ agonists facilitated the cell surface abundance of TβRII and IL-2Rα via N-linked glycosylation, thereby activating TGF-β/Smads and IL-2/STAT5 signaling, and the connection between N-linked glycosylation and Treg responses was revealed by tunicamycin. However, the increased surface abundance of CD36 was demonstrated to be mainly owing to PPARγ agonists-up-regulated overall expression. Finally, PPARγ antagonist GW9662 or CRISPR/Cas9-mediated knockout of PPARγ constrained the effects of rosiglitazone, 15d-PGJ2 and morin, confirming the exact role of PPARγ.

CONCLUSIONS

The activation of PPARγ enhances Treg responses through up-regulating CD36/CPT1-mediated fatty acid oxidation and subsequent N-glycan branching of TβRII/IL-2Rα, which is beneficial for inflammatory and autoimmune diseases. Video Abstract.

Genetic Modifiers of Thymic Selection and Central Tolerance in Type 1 Diabetes

Type 1 diabetes (T1D) is caused by the T cell-driven autoimmune destruction of insulin-producing cells in the pancreas. T1D served as the prototypical autoimmune disease for genome wide association studies (GWAS) after having already been the subject of many linkage and association studies prior to the development of GWAS technology. Of the many T1D-associated gene variants, a minority appear disease-specific, while most are shared with one or more other autoimmune condition. Shared disease variants suggest defects in fundamental aspects of immune tolerance. The first layer of protective tolerance induction is known as central tolerance and takes place during the thymic selection of T cells. In this article, we will review candidate genes for type 1 diabetes whose function implicates them in central tolerance. We will describe examples of gene variants that modify the function of T cells intrinsically and others that indirectly affect thymic selection. Overall, these insights will show that a significant component of the genetic risk for T1D - and autoimmunity in general - pertains to the earliest stages of tolerance induction, at a time when protective intervention may not be feasible.

The Importance of the Transcription Factor Foxp3 in the Development of Primary Immunodeficiencies

Transcription factors are an extremely important group of proteins that are responsible for the process of selective activation or deactivation of other cellular proteins, usually at the last stage of signal transmission in the cell. An important family of transcription factors that regulate the body’s response is the FOX family which plays an important role in regulating the expression of genes involved in cell growth, proliferation, and differentiation. The members of this family include the intracellular protein Foxp3, which regulates the process of differentiation of the T lymphocyte subpopulation, and more precisely, is responsible for the development of regulatory T lymphocytes. This protein influences several cellular processes both directly and indirectly. In the process of cytokine production regulation, the Foxp3 protein interacts with numerous proteins and transcription factors such as NFAT, nuclear factor kappa B, and Runx1/AML1 and is involved in the process of histone acetylation in condensed chromatin. Malfunctioning of transcription factor Foxp3 caused by the mutagenesis process affects the development of disorders of the immune response and autoimmune diseases. This applies to the impairment or inability of the immune system to fight infections due to a disruption of the mechanisms supporting immune homeostasis which in turn leads to the development of a special group of disorders called primary immunodeficiencies (PID). The aim of this review is to provide information on the role of the Foxp3 protein in the human body and its involvement in the development of two types of primary immunodeficiency diseases: IPEX (Immunodysregulation Polyendocrinopathy Enteropathy X-linked syndrome) and CVID (Common Variable Immunodeficiency).

Control of Foxp3 induction and maintenance by sequential histone acetylation and DNA demethylation

Regulatory T (T_reg) cells play crucial roles in suppressing deleterious immune response. Here, we investigate how T_reg cells are mechanistically induced in vitro (iT_reg) and stabilized via transcriptional regulation of T_reg lineage-specifying factor Foxp3. We find that acetylation of histone tails at the Foxp3 promoter is required for inducing Foxp3 transcription. Upon induction, histone acetylation signals via bromodomain-containing proteins, particularly targets of inhibitor JQ1, and sustains Foxp3 transcription via a global or trans effect. Subsequently, Tet-mediated DNA demethylation of Foxp3 cis-regulatory elements, mainly enhancer CNS2, increases chromatin accessibility and protein binding, stabilizing Foxp3 transcription and obviating the need for the histone acetylation signal. These processes transform stochastic iT_reg induction into a stable cell fate, with the former sensitive and the latter resistant to genetic and environmental perturbations. Thus, sequential histone acetylation and DNA demethylation in Foxp3 induction and maintenance reflect stepwise mechanical switches governing iT_reg cell lineage specification.

Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED), also known as autoimmune polyglandular syndrome type-1 (APS-1), is a rare monogenic autoimmune disease caused by loss-of-function mutations in the autoimmune regulator (AIRE) gene. AIRE deficiency impairs immune tolerance in the thymus and results in the peripheral escape of self-reactive T lymphocytes and the generation of several cytokine- and tissue antigen-targeted autoantibodies. APECED features a classic triad of characteristic clinical manifestations consisting of chronic mucocutaneous candidiasis (CMC), hypoparathyroidism, and primary adrenal insufficiency (Addison's disease). In addition, APECED patients develop several non-endocrine autoimmune manifestations with variable frequencies, whose recognition by pediatricians should facilitate an earlier diagnosis and allow for the prompt implementation of targeted screening, preventive, and therapeutic strategies. This review summarizes our current understanding of the genetic, immunological, clinical, diagnostic, and treatment features of APECED.

Foxp3 enhancers synergize to maximize regulatory T cell suppressive capacity

T reg cells bearing a diverse antigen receptor repertoire suppress pathogenic T cells and maintain immune homeostasis during their long lifespan. How their robust function is determined genetically remains elusive. Here, we investigate the regulatory space of the cis-regulatory elements of T reg lineage-specifying factor Foxp3. Foxp3 enhancers are known as distinct readers of environmental cues controlling T reg cell induction or lineage stability. However, their single deficiencies cause mild, if any, immune dysregulation, leaving the key transcriptional mechanisms determining Foxp3 expression and thereby T reg cell suppressive capacity uncertain. We examined the collective activities of Foxp3 enhancers and found that they coordinate to maximize T reg cell induction, Foxp3 expression level, or lineage stability through distinct modes and that ablation of synergistic enhancers leads to lethal autoimmunity in young mice. Thus, the induction and maintenance of a diverse, stable T reg cell repertoire rely on combinatorial Foxp3 enhancers, suggesting broad, stage-specific, synergistic activities of cell-intrinsic factors and cell-extrinsic cues in determining T reg cell suppressive capacity.

Regulatory T Cells-Related Genes Are under DNA Methylation Influence

Regulatory T cells (Tregs) exert a highly suppressive function in the immune system. Disturbances in their function predispose an individual to autoimmune dysregulation, with a predominance of the pro-inflammatory environment. Besides Foxp3, which is a master regulator of these cells, other genes (e.g., Il2ra, Ctla4, Tnfrsf18, Ikzf2, and Ikzf4) are also involved in Tregs development and function. Multidimensional Tregs suppression is determined by factors that are believed to be crucial in the action of Tregs-related genes. Among them, epigenetic changes, such as DNA methylation, tend to be widely studied over the past few years. DNA methylation acts as a repressive mark, leading to diminished gene expression. Given the role of increased CpG methylation upon Tregs imprinting and functional stability, alterations in the methylation pattern can cause an imbalance in the immune response. Due to the fact that epigenetic changes can be reversible, so-called epigenetic modifiers are broadly used in order to improve Tregs performance. In this review, we place emphasis on the role of DNA methylation of the genes that are key regulators of Tregs function. We also discuss disease settings that have an impact on the methylation status of Tregs and systematize the usefulness of epigenetic drugs as factors able to influence Tregs functions.

Distinct Foxp3 enhancer elements coordinate development, maintenance, and function of regulatory T cells

The transcription factor Foxp3 plays crucial roles for Treg cell development and function. Conserved non-coding sequences (CNSs) at the Foxp3 locus control Foxp3 transcription, but how they developmentally contribute to Treg cell lineage specification remains obscure. Here, we show that among Foxp3 CNSs, the promoter-upstream CNS0 and the intergenic CNS3, which bind distinct transcription factors, were activated at early stages of thymocyte differentiation prior to Foxp3 promoter activation, with sequential genomic looping bridging these regions and the promoter. While deletion of either CNS0 or CNS3 partially compromised thymic Treg cell generation, deletion of both completely abrogated the generation and impaired the stability of Foxp3 expression in residual Treg cells. As a result, CNS0 and CNS3 double-deleted mice succumbed to lethal systemic autoimmunity and inflammation. Thus, hierarchical and coordinated activation of Foxp3 CNS0 and CNS3 initiates and stabilizes Foxp3 gene expression, thereby crucially controlling Treg cell development, maintenance, and consequently immunological self-tolerance.