Genetic tracing reveals transcription factor Foxp3-dependent and Foxp3-independent functionality of peripherally induced Treg cells

How bile acids and the microbiota interact to shape host immunity

Bile acids are increasingly appearing in the spotlight owing to their novel impacts on various host processes. Similarly, there is growing attention on members of the microbiota that are responsible for bile acid modifications. With recent advances in technology enabling the discovery and continued identification of microbially conjugated bile acids, the chemical complexity of the bile acid landscape in the body is increasing at a rapid pace. In this Review, we summarize our current understanding of how bile acids and the gut microbiota interact to modulate immune responses during homeostasis and disease, with a particular focus on the gut.

Discovery of a proteolysis targeting chimera (PROTAC) as a potent regulator of FOXP3

Regulatory T (Treg) cells play a central role in immune homeostasis. Forkhead box P3 (Foxp3), a hallmark molecule in Treg cells, is a vital transcription factor for their development and function. Studies have shown that degradation of the Foxp3 could provide therapeutic benefits in achieving effective anti-tumor immunity. In this study, we designed three PROTAC molecules, P60-L1-VHL, P60-L2-VHL, and P60-L3-VHL, based on a 15-mer peptide inhibitor of Foxp3 (P60), and explored their potential in regulating Foxp3 expression and function. Our data show that, among these molecules, P60-L3-VHL can inhibit the expression and nuclear localization of Foxp3 in HEK 293 T and HeLa cells, respectively. Meanwhile, use of proteasome inhibitor in P60-L3-VHL treated cells revealed an increased Foxp3 expression, indicating that P60-L3-VHL mediates the inhibition of Foxp3 through its degradation in the proteasome pathway. We further substantiate that P60-L3-VHL reduces the differentiation and Foxp3 expression in the in-vitro activated Treg cells. Overall, our findings suggest that P60-L3-VHL inhibits the differentiation of Treg cells by degrading the Foxp3, which may have potential implications in cancer immunotherapy.

Tryptophan Metabolism in Alzheimer's Disease with the Involvement of Microglia and Astrocyte Crosstalk and Gut-Brain Axis

Alzheimer's disease (AD) is an age-dependent neurodegenerative disease characterized by extracellular Amyloid Aβ peptide (Aβ) deposition and intracellular Tau protein aggregation. Glia, especially microglia and astrocytes are core participants during the progression of AD and these cells are the mediators of Aβ clearance and degradation. The microbiota-gut-brain axis (MGBA) is a complex interactive network between the gut and brain involved in neurodegeneration. MGBA affects the function of glia in the central nervous system (CNS), and microbial metabolites regulate the communication between astrocytes and microglia; however, whether such communication is part of AD pathophysiology remains unknown. One of the potential links in bilateral gut-brain communication is tryptophan (Trp) metabolism. The microbiota-originated Trp and its metabolites enter the CNS to control microglial activation, and the activated microglia subsequently affect astrocyte functions. The present review highlights the role of MGBA in AD pathology, especially the roles of Trp per se and its metabolism as a part of the gut microbiota and brain communications. We (i) discuss the roles of Trp derivatives in microglia-astrocyte crosstalk from a bioinformatics perspective, (ii) describe the role of glia polarization in the microglia-astrocyte crosstalk and AD pathology, and (iii) summarize the potential of Trp metabolism as a therapeutic target. Finally, we review the role of Trp in AD from the perspective of the gut-brain axis and microglia, as well as astrocyte crosstalk, to inspire the discovery of novel AD therapeutics.

The renaissance of oral tolerance: merging tradition and new insights

Oral tolerance is the process by which feeding of soluble proteins induces antigen-specific systemic immune unresponsiveness. Oral tolerance is thought to have a central role in suppressing immune responses to 'harmless' food antigens, and its failure can lead to development of pathologies such as food allergies or coeliac disease. However, on the basis of long-standing experimental observations, the relevance of oral tolerance in human health has achieved new prominence recently following the discovery that oral administration of peanut proteins prevents the development of peanut allergy in at-risk human infants. In this Review, we summarize the new mechanistic insights into three key processes necessary for the induction of tolerance to oral antigens: antigen uptake and transport across the small intestinal epithelial barrier to the underlying immune cells; the processing, transport and presentation of fed antigen by different populations of antigen-presenting cells; and the development of immunosuppressive T cell populations that mediate antigen-specific tolerance. In addition, we consider how related but distinct processes maintain tolerance to bacterial antigens in the large intestine. Finally, we outline the molecular mechanisms and functional consequences of failure of oral tolerance and how these may be modulated to enhance clinical outcomes and prevent disease.

An integrated transcription factor framework for Treg identity and diversity

Vertebrate cell identity depends on the combined activity of scores of transcription factors (TF). While TFs have often been studied in isolation, a systematic perspective on their integration has been missing. Focusing on FoxP3+ regulatory T cells (Tregs), key guardians of immune tolerance, we combined single-cell chromatin accessibility, machine learning, and high-density genetic variation, to resolve a validated framework of diverse Treg chromatin programs, each shaped by multi-TF inputs. This framework identified previously unrecognized Treg controllers (Smarcc1) and illuminated the mechanism of action of FoxP3, which amplified a pre-existing Treg identity, diversely activating or repressing distinct programs, dependent on different regulatory partners. Treg subpopulations in the colon relied variably on FoxP3, Helios+ Tregs being completely dependent, but RORγ+ Tregs largely independent. These differences were rooted in intrinsic biases decoded by the integrated framework. Moving beyond master regulators, this work unravels how overlapping TF activities coalesce into Treg identity and diversity.

Pathogenic mechanisms in the evolution of food allergy

The early development of the neonatal immune system is profoundly influenced by exposure to dietary and microbial antigens, which shapes mucosal tolerance. Successful oral tolerance induction is crucially dependent on microbially imprinted immune cells, most notably the RORγt+ regulatory T (Treg) and antigen presenting cells and is essential for preventing food allergy (FA). The development of FA can be envisioned to result from disruptions at key checkpoints (CKPTs) that govern oral tolerance induction. These include gut epithelial sensory and effector circuits that when dysregulated promote pro-allergic gut dysbiosis. They also include microbially imprinted immune regulatory circuits that are disrupted by dysbiosis and pro-allergic immune responses unleashed by the dysregulation of the aforementioned cascades. Understanding these checkpoints is essential for developing therapeutic strategies to restore immune homeostasis in FA.

Neoantigen-specific cytotoxic Tr1 CD4 T cells suppress cancer immunotherapy

CD4+ T cells can either enhance or inhibit tumour immunity. Although regulatory T cells have long been known to impede antitumour responses1-5, other CD4+ T cells have recently been implicated in inhibiting this response6,7. Yet, the nature and function of the latter remain unclear. Here, using vaccines containing MHC class I (MHC-I) neoantigens (neoAgs) and different doses of tumour-derived MHC-II neoAgs, we discovered that whereas the inclusion of vaccines with low doses of MHC-II-restricted peptides (LDVax) promoted tumour rejection, vaccines containing high doses of the same MHC-II neoAgs (HDVax) inhibited rejection. Characterization of the inhibitory cells induced by HDVax identified them as type 1 regulatory T (Tr1) cells expressing IL-10, granzyme B, perforin, CCL5 and LILRB4. Tumour-specific Tr1 cells suppressed tumour rejection induced by anti-PD1, LDVax or adoptively transferred tumour-specific effector T cells. Mechanistically, HDVax-induced Tr1 cells selectively killed MHC-II tumour antigen-presenting type 1 conventional dendritic cells (cDC1s), leading to low numbers of cDC1s in tumours. We then documented modalities to overcome this inhibition, specifically via anti-LILRB4 blockade, using a CD8-directed IL-2 mutein, or targeted loss of cDC2/monocytes. Collectively, these data show that cytotoxic Tr1 cells, which maintain peripheral tolerance, also inhibit antitumour responses and thereby function to impede immune control of cancer.

Regulatory T cells in the context: deciphering the dynamic interplay with the tissue environment

The delicate balance between protective immunity against pathogens and the prevention of autoimmunity requires finely tuned generation and function of regulatory CD4+ T (Treg) cells. Here, we review recent progress in the understanding of a complex set of cues, which converge on Treg cells in lymphoid and nonlymphoid organs and in tumors and how these cues modulate Treg functions. We highlight the versatility of Treg cells underlying their ability to dynamically adapt to local microenvironments and perform a wide range of functions that extend beyond the archetypal role of Treg cells in moderating adverse effects of immune response-associated inflammation and in suppressing autoimmunity.

Radiomics Features on Enhanced Computed Tomography Predict FOXP3 Expression and Clinical Prognosis in Patients with Head and Neck Squamous Cell Carcinoma

Forkhead box P3 (FOXP3) has been identified as a novel molecular marker in various types of cancer. The present study assessed the expression of FOXP3 in patients with head and neck squamous cell carcinoma (HNSCC) and its potential as a clinical prognostic indicator, and developed a radiomics model based on enhanced computed tomography (CT) imaging. Data from 483 patients with HNSCC were downloaded from the Cancer Genome Atlas for FOXP3 prognostic analysis and enhanced CT images from 139 patients included in the Cancer Imaging Archives, which were subjected to the maximum relevance and minimum redundancy and recursive feature elimination algorithms for radiomics feature extraction and processing. Logistic regression was used to build a model for predicting FOXP3 expression. A prognostic scoring system for radiomics score (RS), FOXP3, and patient clinicopathological factors was established to predict patient survival. The area under the receiver operating characteristic (ROC) curve (AUC) and calibration curve and decision curve analysis (DCA) were used to evaluate model performance. Furthermore, the relationship between FOXP3 and the immune microenvironment, as well as the association between RS and immune checkpoint-related genes, was analyzed. Results of analysis revealed that patients with HNSCC and high FOXP3 mRNA expression exhibited better overall survival. Immune infiltration analysis revealed that FOXP3 had a positive correlation with CD4 + and CD8 + T cells and other immune cells. The 8 best radiomics features were selected to construct the radiomics model. In the FOXP3 expression prediction model, the AUC values were 0.707 and 0.702 for the training and validation sets, respectively. Additionally, the calibration curve and DCA demonstrated the positive diagnostic utility of the model. RS was correlated with immune checkpoint-related genes such as ICOS, CTLA4, and PDCD1. A predictive nomogram was established, the AUCs were 0.87, 0.787, and 0.801 at 12, 24, and 36 months, respectively, and DCA demonstrated the high clinical applicability of the nomogram. The enhanced CT radiomics model can predict expression of FOXP3 and prognosis in patients with HNSCC. As such, FOXP3 may be used as a novel prognostic marker to improve individualized clinical diagnosis and treatment decisions.

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.

Early life imprinting of intestinal immune tolerance and tissue homeostasis

Besides its canonical role in protecting the host from pathogens, the immune system plays an arguably equally important role in maintaining tissue homeostasis. Within barrier tissues that interface with the external microenvironment, induction of immune tolerance to innocuous antigens, such as commensal, dietary, and environmental antigens, is key to establishing immune homeostasis. The early postnatal period represents a critical window of opportunity in which parallel development of the tissue, immune cells, and microbiota allows for reciprocal regulation that shapes the long-term immunological tone of the tissue and subsequent risk of immune-mediated diseases. During early infancy, the immune system appears to sacrifice pro-inflammatory functions, prioritizing the establishment of tissue tolerance. In this review, we discuss mechanisms underlying early life windows for intestinal tolerance with a focus on newly identified RORγt+ antigen-presenting cells-Thetis cells-and highlight the role of the intestinal microenvironment in shaping intestinal immune system development and tolerance.

Blimp-1 and c-Maf regulate immune gene networks to protect against distinct pathways of pathobiont-induced colitis

Intestinal immune responses to microbes are controlled by the cytokine IL-10 to avoid immune pathology. Here, we use single-cell RNA sequencing of colon lamina propria leukocytes (LPLs) along with RNA-seq and ATAC-seq of purified CD4+ T cells to show that the transcription factors Blimp-1 (encoded by Prdm1) and c-Maf co-dominantly regulate Il10 while negatively regulating proinflammatory cytokines in effector T cells. Double-deficient Prdm1fl/flMaffl/flCd4Cre mice infected with Helicobacter hepaticus developed severe colitis with an increase in TH1/NK/ILC1 effector genes in LPLs, while Prdm1fl/flCd4Cre and Maffl/flCd4Cre mice exhibited moderate pathology and a less-marked type 1 effector response. LPLs from infected Maffl/flCd4Cre mice had increased type 17 responses with increased Il17a and Il22 expression and an increase in granulocytes and myeloid cell numbers, resulting in increased T cell-myeloid-neutrophil interactions. Genes over-expressed in human inflammatory bowel disease showed differential expression in LPLs from infected mice in the absence of Prdm1 or Maf, revealing potential mechanisms of human disease.

Donor regulatory T cells rapidly adapt to recipient tissues to control murine acute graft-versus-host disease

The adoptive transfer of regulatory T cells is a promising strategy to prevent graft-versus-host disease after allogeneic bone marrow transplantation. Here, we use a major histocompatibility complex-mismatched mouse model to follow the fate of in vitro expanded donor regulatory T cells upon migration to target organs. Employing comprehensive gene expression and repertoire profiling, we show that they retain their suppressive function and plasticity after transfer. Upon entering non-lymphoid tissues, donor regulatory T cells acquire organ-specific gene expression profiles resembling tissue-resident cells and activate hallmark suppressive and cytotoxic pathways, most evidently in the colon, when co-transplanted with graft-versus-host disease-inducing conventional T cells. Dominant T cell receptor clonotypes overlap between organs and across recipients and their relative abundance correlates with protection efficacy. Thus, this study reveals donor regulatory T cell selection and adaptation mechanisms in target organs and highlights protective features of Treg to guide the development of improved graft-versus-host disease prevention strategies.

Role of regulatory T cells in mouse lung development

Regulatory T cells (Tregs) constitute a specialized subset of T cells with dual immunoregulatory and modulatory functions. Recent studies have reported that Tregs mediate immune responses and regulate the development and repair processes in non-lymphoid tissues, including bone and cardiac muscle. Additionally, Tregs facilitate the repair and regeneration of damaged lung tissues. However, limited studies have examined the role of Tregs in pulmonary development. This study aimed to evaluate the role of Tregs in pulmonary development by investigating the dynamic alterations in Tregs and their hallmark cellular factor Forkhead box P3 (Foxp3) at various stages of murine lung development and establishing a murine model of anti-CD25 antibody-induced Treg depletion. During the early stages of murine lung development, especially the canalicular and saccular stages, the levels of Treg abundance and expression of Foxp3 and transforming growth factor-β (TGF-β) were upregulated. This coincided with the proliferation period of alveolar epithelial cells and vascular endothelial cells, indicating an adaptation to the dynamic lung developmental processes. Furthermore, the depletion of Tregs disrupted lung tissue morphology and downregulated lung development-related factors, such as surfactant protein C (SFTPC), vascular endothelial growth factor A (VEGFA) and platelet endothelial cell adhesion molecule-1 (PECAM1/CD31). These findings suggest that Tregs promote murine lung development.

CKLF instigates a "cold" microenvironment to promote MYCN-mediated tumor aggressiveness

Solid tumors, especially those with aberrant MYCN activation, often harbor an immunosuppressive microenvironment to fuel malignant growth and trigger treatment resistance. Despite this knowledge, there are no effective strategies to tackle this problem. We found that chemokine-like factor (CKLF) is highly expressed by various solid tumor cells and transcriptionally up-regulated by MYCN. Using the MYCN-driven high-risk neuroblastoma as a model system, we demonstrated that as early as the premalignant stage, tumor cells secrete CKLF to attract CCR4-expressing CD4+ cells, inducing immunosuppression and tumor aggression. Genetic depletion of CD4+ T regulatory cells abolishes the immunorestrictive and protumorigenic effects of CKLF. Our work supports that disrupting CKLF-mediated cross-talk between tumor and CD4+ suppressor cells represents a promising immunotherapeutic approach to battling MYCN-driven tumors.

Role of Treg cell subsets in cardiovascular disease pathogenesis and potential therapeutic targets

In the genesis and progression of cardiovascular diseases involving both innate and adaptive immune responses, inflammation plays a pivotal and dual role. Studies in experimental animals indicate that certain immune responses are protective, while others exacerbate the disease. T-helper (Th) 1 cell immune responses are recognized as key drivers of inflammatory progression in cardiovascular diseases. Consequently, the CD4+CD25+FOXP3+ regulatory T cells (Tregs) are gaining increasing attention for their roles in inflammation and immune regulation. Given the critical role of Tregs in maintaining immune-inflammatory balance and homeostasis, abnormalities in their generation or function might lead to aberrant immune responses, thereby initiating pathological changes. Numerous preclinical studies and clinical trials have unveiled the central role of Tregs in cardiovascular diseases, such as atherosclerosis. Here, we review the roles and mechanisms of Treg subsets in cardiovascular conditions like atherosclerosis, hypertension, myocardial infarction and remodeling, myocarditis, dilated cardiomyopathy, and heart failure. While the precise molecular mechanisms of Tregs in cardiac protection remain elusive, therapeutic strategies targeting Tregs present a promising new direction for the prevention and treatment of cardiovascular diseases.

Epigenetic signature and key transcriptional regulators of human antigen-specific type 1 regulatory T cells

Human adaptive immunity is orchestrated by effector and regulatory T (Treg) cells. Natural Tregs arise in the thymus where they are shaped to recognize self-antigens, while type 1 Tregs or Tr1 cells are induced from conventional peripheral CD4 + T cells in response to peripheral antigens, such as alloantigens and allergens. Tr1 cells have been developed as a potential therapy for inducing antigen-specific tolerance, because they can be rapidly differentiated in vitro in response to a target antigen. However, the epigenetic landscape and the identity of transcription factors (TFs) that regulate differentiation, phenotype, and functions of human antigen-specific Tr1 cells is largely unknown, hindering Tr1 research and broader clinical development. Here, we reveal the unique epigenetic signature of antigen-specific Tr1 cells, and TFs that regulate their differentiation, phenotype and function. We showed that in vitro induced antigen-specific Tr1 cells are distinct both clonally and transcriptionally from natural Tregs and other conventional CD4 + T cells on a single-cell level. An integrative analysis of Tr1 cell epigenome and transcriptome identified a TF signature unique to antigen-specific Tr1 cells, and predicted that IRF4, BATF, and MAF act as their transcriptional regulators. Using functional genomics, we showed that each of these TFs play a non-redundant role in regulating Tr1 cell differentiation, suppressive function, and expression of co-inhibitory and cytotoxic proteins. By using the Tr1-specific TF signature as a molecular fingerprint, we tracked Tr1 cells in peripheral blood of recipients of allogeneic hematopoietic stem cell transplantation treated with adoptive Tr1 cell therapy. Furthermore, the same signature identified Tr1 cells in resident CD4 + T cells in solid tumors. Altogether, these results reveal the epigenetic signature and the key transcriptional regulators of human Tr1 cells. These data will guide mechanistic studies of human Tr1 cell biology and the development and optimization of adoptive Tr1 cell therapies.

Applications of Intravital Imaging in Cancer Immunotherapy

Currently, immunotherapy is one of the most effective treatment strategies for cancer. However, the efficacy of any specific anti-tumor immunotherapy can vary based on the dynamic characteristics of immune cells, such as their rate of migration and cell-to-cell interactions. Therefore, understanding the dynamics among cells involved in the immune response can inform the optimization and improvement of existing immunotherapy strategies. In vivo imaging technologies use optical microscopy techniques to visualize the movement and behavior of cells in vivo, including cells involved in the immune response, thereby showing great potential for application in the field of cancer immunotherapy. In this review, we briefly introduce the technical aspects required for in vivo imaging, such as fluorescent protein labeling, the construction of transgenic mice, and various window chamber models. Then, we discuss the elucidation of new phenomena and mechanisms relating to tumor immunotherapy that has been made possible by the application of in vivo imaging technology. Specifically, in vivo imaging has supported the characterization of the movement of T cells during immune checkpoint inhibitor therapy and the kinetic analysis of dendritic cell migration in tumor vaccine therapy. Finally, we provide a perspective on the challenges and future research directions for the use of in vivo imaging technology in cancer immunotherapy.

Kuijieling decoction regulates the Treg/Th17 cell balance in ulcerative colitis through the RA/RARα signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Ulcerative colitis (UC) is an idiopathic intestinal disease characterized by chronic inflammation with unknown etiology. Kuijieling decoction is a traditional Chinese Medicine with unique therapeutic efficacy for UC.

AIM OF THE STUDY

To validate the effects of Kuijieling decoction on vitamin A metabolism and retinoic acid (RA) production, along with evaluation of its immunomodulatory activity, and further clarify the upstream mechanisms underlying Treg/Th17 regulation that contribute to therapeutic effects against UC.

MATERIALS AND METHODS

Network pharmacology and molecular docking analyses were employed to predict the potential anti-UC targets of Kuijieling and associated pathways. A rat model of UC was generated by treatment with trinitrobenzene sulfonic acid (TNBS) to induce inflammation. T lymphocytes were induced to differentiate into Th17 via combined stimulation with the cytokines TGF-β1, IL-6 and IL-23. Expression levels of RA/RARα-related factors (RARα, CRABPII, Smad3, IL-6R and IL-23R) and Treg/Th17 cell-related factors (Foxp3, RORγt) were measured via western blot (WB), quantitative real-time PCR (RT-qPCR), and immunohistochemistry analyses. Components of the vitamin A metabolic pathway (vitamin A, retinol, retinoic acid) and Treg/Th17 cell-related cytokines (IL-10, IL-17, IL-21) were evaluated using ELISA. Flow cytometry was performed to determine the percentages of Treg and Th17 cells.

RESULTS

The action targets of Kuijieling were significantly associated with T cell activation, Th17 cell differentiation and the immune response. IL-2, IL-6, STAT3 and RARα displayed strong binding affinities with the main components of Kuijieling, suggesting an important role in its therapeutic efficacy. Kuijieling promoted vitamin A metabolism and RA/RARα signaling in UC rats and T lymphocytes. Moreover, Kuijieling effectively regulated the Treg/Th17 cell balance in UC rats and T lymphocytes and relieved inflammation. The protective effect of Kuijieling was weakened after inhibition of the RA/RARα signaling pathway.

CONCLUSIONS

Kuijieling promotes vitamin A metabolism and RA synthesis, enhances interactions between RA, intracellular binding protein CRABPII and nuclear receptor RARα, and upregulates Smad3 and Foxp3, thus promoting Treg differentiation. Simultaneously, Kuijieling inhibited expression of IL-6R and IL-23R genes and production of RORγt, leading to suppression of Th17 differentiation, and ultimately, reduction of the Th17/Treg cell ratio.

Oleic acid availability impacts thymocyte preprogramming and subsequent peripheral Treg cell differentiation

The nature of activation signals is essential in determining T cell subset differentiation; however, the features that determine T cell subset preference acquired during intrathymic development remain elusive. Here we show that naive CD4+ T cells generated in the mouse thymic microenvironment lacking Scd1, encoding the enzyme catalyzing oleic acid (OA) production, exhibit enhanced regulatory T (Treg) cell differentiation and attenuated development of experimental autoimmune encephalomyelitis. Scd1 deletion in K14+ thymic epithelia recapitulated the enhanced Treg cell differentiation phenotype of Scd1-deficient mice. The dearth of OA permitted DOT1L to increase H3K79me2 levels at the Atp2a2 locus of thymocytes at the DN2-DN3 transition stage. Such epigenetic modification persisted in naive CD4+ T cells and facilitated Atp2a2 expression. Upon T cell receptor activation, ATP2A2 enhanced the activity of the calcium-NFAT1-Foxp3 axis to promote naive CD4+ T cells to differentiate into Treg cells. Therefore, OA availability is critical for preprogramming thymocytes with Treg cell differentiation propensities in the periphery.

Homeostatic, repertoire and transcriptional relationships between colon T regulatory cell subsets

Foxp3+ regulatory T cells (Tregs) in the colon are key to promoting peaceful coexistence with symbiotic microbes. Differentiated in either thymic or peripheral locations, and modulated by microbes and other cellular influencers, colonic Treg subsets have been identified through key transcription factors (TFs; Helios, Rorγ, Gata3, and cMaf), but their interrelationships are unclear. Applying a multimodal array of immunologic, genomic, and microbiological assays, we find more overlap than expected between populations. The key TFs (Rorγ, Helios, Gata3, and cMaf) play different roles, some essential for subset identity, others driving functional gene signatures. Functional divergence was clearest under challenge. Single-cell genomics revealed a spectrum of phenotypes between the Helios+ and Rorγ+ poles, different Treg-inducing bacteria inducing the same Treg phenotypes to varying degrees, not distinct populations. TCR repertoires in monocolonized mice revealed that Helios+ and Rorγ+ Tregs are related and cannot be uniquely equated to tTreg and pTreg. Comparison of spleen and colon repertoires revealed that 2 to 5% of clonotypes are shared between the locations. We propose that rather than the origin of their differentiation, tissue-specific cues dictate the spectrum of colonic Treg phenotypes.

Dietary L-Tryptophan consumption determines the number of colonic regulatory T cells and susceptibility to colitis via GPR15

Environmental factors are the major contributor to the onset of immunological disorders such as ulcerative colitis. However, their identities remain unclear. Here, we discover that the amount of consumed L-Tryptophan (L-Trp), a ubiquitous dietary component, determines the transcription level of the colonic T cell homing receptor, GPR15, hence affecting the number of colonic FOXP3+ regulatory T (Treg) cells and local immune homeostasis. Ingested L-Trp is converted by host IDO1/2 enzymes, but not by gut microbiota, to compounds that induce GPR15 transcription preferentially in Treg cells via the aryl hydrocarbon receptor. Consequently, two weeks of dietary L-Trp supplementation nearly double the colonic GPR15+ Treg cells via GPR15-mediated homing and substantially reduce the future risk of colitis. In addition, humans consume 3-4 times less L-Trp per kilogram of body weight and have fewer colonic GPR15+ Treg cells than mice. Thus, we uncover a microbiota-independent mechanism linking dietary L-Trp and colonic Treg cells, that may have therapeutic potential.

Regulatory T cells in the face of the intestinal microbiota

Regulatory T cells (Treg cells) are key players in ensuring a peaceful coexistence with microorganisms and food antigens at intestinal borders. Startling new information has appeared in recent years on their diversity, the importance of the transcription factor FOXP3, how T cell receptors influence their fate and the unexpected and varied cellular partners that influence Treg cell homeostatic setpoints. We also revisit some tenets, maintained by the echo chambers of Reviews, that rest on uncertain foundations or are a subject of debate.

Regulatory T cells in allergic inflammation

Regulatory T (Treg) cells maintain immune tolerance to allergens at the environmental interfaces in the airways, skin and gut, marshalling in the process distinct immune regulatory circuits operative in the respective tissues. Treg cells are coordinately mobilized with allergic effector mechanisms in the context of a tissue-protective allergic inflammatory response against parasites, toxins and potentially harmful allergens, serving to both limit the inflammation and promote local tissue repair. Allergic diseases are associated with subverted Treg cell responses whereby a chronic allergic inflammatory environment can skew Treg cells toward pathogenic phenotypes that both perpetuate and aggravate disease. Interruption of Treg cell subversion in chronic allergic inflammatory conditions may thus provide novel therapeutic strategies by re-establishing effective immune regulation.

Intestinal factors promoting the development of RORγt+ cells and oral tolerance

The gastrointestinal tract has to harmonize the two seemingly opposite functions of fulfilling nutritional needs and avoiding the entry of pathogens, toxins and agents that can cause physical damage. This balance requires a constant adjustment of absorptive and defending functions by sensing environmental changes or noxious substances and initiating adaptive or protective mechanisms against them through a complex network of receptors integrated with the central nervous system that communicate with cells of the innate and adaptive immune system. Effective homeostatic processes at barrier sites take the responsibility for oral tolerance, which protects from adverse reactions to food that cause allergic diseases. During a very specific time interval in early life, the establishment of a stable microbiota in the large intestine is sufficient to prevent pathological events in adulthood towards a much larger bacterial community and provide tolerance towards diverse food antigens encountered later in life. The beneficial effects of the microbiome are mainly exerted by innate and adaptive cells that express the transcription factor RORγt, in whose generation, mediated by different bacterial metabolites, retinoic acid signalling plays a predominant role. In addition, recent investigations indicate that food antigens also contribute, analogously to microbial-derived signals, to educating innate immune cells and instructing the development and function of RORγt+ cells in the small intestine, complementing and expanding the tolerogenic effect of the microbiome in the colon. This review addresses the mechanisms through which microbiota-produced metabolites and dietary antigens maintain intestinal homeostasis, highlighting the complementarity and redundancy between their functions.

Umbilical cord blood and peripheral blood-derived regulatory T cells therapy: Progress in type 1 diabetes

Regulatory T cells (Tregs) are key regulators for the inflammatory response and play a role in maintaining the immune tolerance. Type 1 diabetes (T1D) is a relatively common autoimmune disease that results from the loss of immune tolerance to β-cell-associated antigens. Preclinical models have demonstrated the safety and efficacy of Tregs given in transplant rejection and autoimmune diseases such as T1D. Adoptive transfer of Tregs has been utilized in clinical trials for over a decade. However, the achievement of the adoptive transfer of Tregs therapy in clinical application remains challenging. In this review, we highlight the characterization of Tregs and compare the differences between umbilical cord blood and adult peripheral blood-derived Tregs. Additionally, we summarize conditional modifications in the expansion of Tregs in clinical trials, especially for the treatment of T1D. Finally, we discuss the existing technical challenges for Tregs in clinical trials for the treatment of T1D.

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.

Intricacies of TGF-β signaling in Treg and Th17 cell biology

Balanced immunity is pivotal for health and homeostasis. CD4+ helper T (Th) cells are central to the balance between immune tolerance and immune rejection. Th cells adopt distinct functions to maintain tolerance and clear pathogens. Dysregulation of Th cell function often leads to maladies, including autoimmunity, inflammatory disease, cancer, and infection. Regulatory T (Treg) and Th17 cells are critical Th cell types involved in immune tolerance, homeostasis, pathogenicity, and pathogen clearance. It is therefore critical to understand how Treg and Th17 cells are regulated in health and disease. Cytokines are instrumental in directing Treg and Th17 cell function. The evolutionarily conserved TGF-β (transforming growth factor-β) cytokine superfamily is of particular interest because it is central to the biology of both Treg cells that are predominantly immunosuppressive and Th17 cells that can be proinflammatory, pathogenic, and immune regulatory. How TGF-β superfamily members and their intricate signaling pathways regulate Treg and Th17 cell function is a question that has been intensely investigated for two decades. Here, we introduce the fundamental biology of TGF-β superfamily signaling, Treg cells, and Th17 cells and discuss in detail how the TGF-β superfamily contributes to Treg and Th17 cell biology through complex yet ordered and cooperative signaling networks.

Tregs in transplantation tolerance: role and therapeutic potential

CD4+ Foxp3+ regulatory T cells (Tregs) are indispensable for preventing autoimmunity, and they play a role in cancer and transplantation settings by restraining immune responses. In this review, we describe evidence for the importance of Tregs in the induction versus maintenance of transplantation tolerance, discussing insights into mechanisms of Treg control of the alloimmune response. Further, we address the therapeutic potential of Tregs as a clinical intervention after transplantation, highlighting engineered CAR-Tregs as well as expansion of donor and host Tregs.

Mutations from patients with IPEX ported to mice reveal different patterns of FoxP3 and Treg dysfunction

Mutations of the transcription factor FoxP3 in patients with "IPEX" (immune dysregulation, polyendocrinopathy, enteropathy, X-linked syndrome) disrupt regulatory T cells (Treg), causing an array of multiorgan autoimmunity. To understand the functional impact of mutations across FoxP3 domains, without genetic and environmental confounders, six human FOXP3 missense mutations are engineered into mice. Two classes of mutations emerge from combined immunologic and genomic analyses. A mutation in the DNA-binding domain shows the same lymphoproliferation and multiorgan infiltration as complete FoxP3 knockouts but delayed by months. Tregs expressing this mutant FoxP3 are destabilized by normal Tregs in heterozygous females compared with hemizygous males. Mutations in other domains affect chromatin opening differently, involving different cofactors and provoking more specific autoimmune pathology (dermatitis, colitis, diabetes), unmasked by immunological challenges or incrossing NOD autoimmune-susceptibility alleles. This work establishes that IPEX disease heterogeneity results from the actual mutations, combined with genetic and environmental perturbations, explaining then the intra-familial variation in IPEX.

Bispecific antibody targeting TGF-β and PD-L1 for synergistic cancer immunotherapy

The PD-1/PD-L1 signaling pathway plays a crucial role in cancer immune evasion, and the use of anti-PD-1/PD-L1 antibodies represents a significant milestone in cancer immunotherapy. However, the low response rate observed in unselected patients and the development of therapeutic resistance remain major obstacles to their clinical application. Accumulating studies showed that overexpressed TGF-β is another immunosuppressive factor apart from traditional immune checkpoints. Actually, the effects of PD-1 and TGF-β pathways are independent and interactive, which work together contributing to the immune evasion of cancer cell. It has been verified that blocking TGF-β and PD-L1 simultaneously could enhance the efficacy of PD-L1 monoclonal antibody and overcome its treatment resistance. Based on the bispecific antibody or fusion protein technology, multiple bispecific and bifunctional antibodies have been developed. In the preclinical and clinical studies, these updated antibodies exhibited potent anti-tumor activity, superior to anti-PD-1/PD-L1 monotherapies. In the review, we summarized the advances of bispecific antibodies targeting TGF-β and PD-L1 in cancer immunotherapy. We believe these next-generation immune checkpoint inhibitors would substantially alter the cancer treatment paradigm, especially in anti-PD-1/PD-L1-resistant patients.

COPD Patients Exhibit Distinct Gene Expression, Accelerated Cellular Aging, and Bias to M2 Macrophages

COPD, one of world's leading contributors to morbidity and mortality, is characterized by airflow limitation and heterogeneous clinical features. Three main phenotypes are proposed: overlapping asthma/COPD (ACO), exacerbator, and emphysema. Disease severity can be classified as mild, moderate, severe, and very severe. The molecular basis of inflammatory amplification, cellular aging, and immune response are critical to COPD pathogenesis. Our aim was to investigate EP300 (histone acetylase, HAT), HDAC 2 (histone deacetylase), HDAC3, and HDAC4 gene expression, telomere length, and differentiation ability to M1/M2 macrophages. For this investigation, 105 COPD patients, 42 smokers, and 73 non-smoker controls were evaluated. We identified a reduced HDAC2 expression in patients with mild, moderate, and severe severity; a reduced HDAC3 expression in patients with moderate and severe severity; an increased HDAC4 expression in patients with mild severity; and a reduced EP300 expression in patients with severe severity. Additionally, HDAC2 expression was reduced in patients with emphysema and exacerbator, along with a reduced HDAC3 expression in patients with emphysema. Surprisingly, smokers and all COPD patients showed telomere shortening. COPD patients showed a higher tendency toward M2 markers. Our data implicate genetic changes in COPD phenotypes and severity, in addition to M2 prevalence, that might influence future treatments and personalized therapies.

Regulation of T cell differentiation and function by long noncoding RNAs in homeostasis and cancer

Long noncoding RNAs (lncRNAs) increase in genomes of complex organisms and represent the largest group of RNA genes transcribed in mammalian cells. Previously considered only transcriptional noise, lncRNAs comprise a heterogeneous class of transcripts that are emerging as critical regulators of T cell-mediated immunity. Here we summarize the lncRNA expression landscape of different T cell subsets and highlight recent advances in the role of lncRNAs in regulating T cell differentiation, function and exhaustion during homeostasis and cancer. We discuss the different molecular mechanisms of lncRNAs and highlight lncRNAs that can serve as novel targets to modulate T cell function or to improve the response to cancer immunotherapies by modulating the immunosuppressive tumor microenvironment.

Homeostatic, repertoire and transcriptional relationships between colon T regulatory cell subsets

Foxp3 + regulatory T cells (Tregs) in the colon are key to promoting peaceful co-existence with symbiotic microbes. Differentiated in either thymic or peripheral locations, and modulated by microbes and other cellular influencers, colonic Treg subsets have been identified through key transcription factors (TF; Helios, Rorg, Gata3, cMaf), but their inter-relationships are unclear. Applying a multimodal array of immunologic, genomic, and microbiological assays, we find more overlap than expected between populations. The key TFs play different roles, some essential for subset identity, others driving functional gene signatures. Functional divergence was clearest under challenge. Single-cell genomics revealed a spectrum of phenotypes between the Helios+ and Rorγ+ poles, different Treg-inducing bacteria inducing the same Treg phenotypes to varying degrees, not distinct populations. TCR clonotypes in monocolonized mice revealed that Helios+ and Rorγ+ Tregs are related, and cannot be uniquely equated to tTreg and pTreg. We propose that rather than the origin of their differentiation, tissue-specific cues dictate the spectrum of colonic Treg phenotypes.

Spatiotemporal regulation of peripheral T cell tolerance

The incomplete removal of T cells that are reactive against self-proteins during their differentiation in the thymus requires mechanisms of tolerance that prevent their effector function within the periphery. A further challenge is imposed by the need to establish tolerance to the holobiont self, which comprises a highly complex community of commensal microorganisms. Here, we review recent advances in the investigation of peripheral T cell tolerance, focusing on new insights into mechanisms of tolerance to the gut microbiota, including tolerogenic antigen-presenting cell types and immunomodulatory lymphocytes, and their layered ontogeny that underlies developmental windows for establishing intestinal tolerance. While emphasizing the intestine as a model tissue for studying peripheral T cell tolerance, we highlight overlapping and distinct pathways that underlie tolerance to self-antigens versus commensal antigens within a broader framework for immune tolerance.

Discovery of Novel Sesquiterpene Lactone Derivatives as Potent PKM2 Activators for the Treatment of Ulcerative Colitis

The pyruvate kinase M2 (PKM2) can significantly affect the differentiation of Th17 and Treg cells; thus, it is considered a promising target for UC therapy. Herein, five series of costunolide (Cos) derivatives are designed, synthesized, and biologically evaluated. Among them, D5 exhibits excellent immunomodulatory activity against T-cell proliferation and potent PKM2 activating activity. Meanwhile, it has been confirmed that D5 can also covalently interact with Cys424 of PKM2. The molecular docking and molecular dynamic (MD) studies indicate that difluorocyclopropyl derivative of D5 improves the protein-ligand interaction by interacting with Arg399 electrostatically. Furthermore, D5 significantly dampens the differentiation of Th17 but not Treg cells to recover the Th17/Treg balance, which is attributed to the suppression of PKM2-mediated glycolysis. Oral administration of D5 ameliorates the symptoms of dextran sulfate sodium (DSS)- and 2,4,6-trinitro-benzenesulfonic acid (TNBS)-induced colitis in mouse model. Collectively, D5 has the potential to be developed as a novel anti-UC candidate.

[Changes in percentage of GATA3+ regulatory T cells and their pathogenic roles in allergic rhinitis]

OBJECTIVE

To investigate the changes in percentage of GATA3+ regulatory T (Treg) cells in patients with allergic rhinitis (AR) and mouse models.

METHODS

The nasal mucosa specimens were obtained from 6 AR patients and 6 control patients for detection of nasal mucosal inflammation. Peripheral blood mononuclear cells (PBMC) were collected from 12 AP patients and 12 control patients to determine the percentages of Treg cells and GATA3+ Treg cells. In a C57BL/6 mouse model of AR, the AR symptom score, peripheral blood OVA-sIgE level, and nasal mucosal inflammation were assessed, and the spleen of mice was collected for detecting the percentages of Treg cells and GATA3+ Treg cells and the expressions of Th2 cytokines.

RESULTS

Compared with the control patients, AR patients showed significantly increased eosinophil infiltration and goblet cell proliferation in the nasal mucosa (P < 0.01) and decreased percentages of Treg cells and GATA3+ Treg cells (P < 0.05). The mouse models of AR also had more obvious allergic symptoms, significantly increased OVA-sIgE level in peripheral blood, eosinophil infiltration and goblet cell hyperplasia (P < 0.01), markedly lowered percentages of Treg cells and GATA3+ Treg cells in the spleen (P < 0.01), and increased expressions of IL-4, IL-6 and IL-10 (P < 0.05).

CONCLUSION

The percentage of GATA3+ Treg cells is decreased in AR patients and mouse models. GATA3+ Treg cells possibly participate in Th2 cell immune response, both of which are involved in the occurrence and progression of AR, suggesting the potential of GATA3+ Treg cells as a new therapeutic target for AR.

Principles of regulatory T cell function

Regulatory T (Treg) cells represent a distinct lineage of cells of the adaptive immune system indispensable for forestalling fatal autoimmune and inflammatory pathologies. The role of Treg cells as principal guardians of the immune system can be attributed to their ability to restrain all currently recognized major types of inflammatory responses through modulating the activity of a wide range of cells of the innate and adaptive immune system. This broad purview over immunity and inflammation is afforded by the multiple modes of action Treg cells exert upon their diverse molecular and cellular targets. Beyond the suppression of autoimmunity for which they were originally recognized, Treg cells have been implicated in tissue maintenance, repair, and regeneration under physiologic and pathologic conditions. Herein, we discuss the current and emerging understanding of Treg cell effector mechanisms in the context of the basic properties of Treg cells that endow them with such functional versatility.

Regulatory T cells as a therapeutic approach for inflammatory bowel disease

Foxp3+ T regulatory (Treg) cells suppress inflammation and are essential for maintaining tissue homeostasis. A growing appreciation of tissue-specific Treg functions has built interest in leveraging the endogenous suppressive mechanisms of these cells into cellular therapeutics in organ-specific diseases. Notably, Treg cells play a critical role in maintaining the intestinal environment. As a barrier site, the gut requires Treg cells to mediate interactions with the microbiota, support barrier integrity, and regulate the immune system. Without fully functional Treg cells, intestinal inflammation and microbial dysbiosis ensue. Thus, there is a particular interest in developing Treg cellular therapies for intestinal inflammatory disease, such as inflammatory bowel disease (IBD). This article reviews some of the critical pathways that are dysregulated in IBD, Treg cell mechanisms of suppression, and the efforts and approaches in the field to develop these cells as a cellular therapy for IBD.

BATF reprograms the tumor immune status

The AP-1 family member BATF maintains immune cell function. Two recent papers by Zhang et al.¹ and Itahashi et al.² investigated the role of this protein in cancer immunity, finding that its depletion in CAR-T cells augments anti-tumor activity and it contributes to Treg-mediated immunosuppression in the tumor microenvironment.

FOXP3 expression diversifies the metabolic capacity and enhances the efficacy of CD8 T cells in adoptive immunotherapy of melanoma

Regulatory T cells overwhelm conventional T cells in the tumor microenvironment (TME) thanks to a FOXP3-driven metabolic program that allows them to engage different metabolic pathways. Using a melanoma model of adoptive T cell therapy (ACT), we show that FOXP3 overexpression in mature CD8 T cells improved their antitumor efficacy, favoring their tumor recruitment, proliferation, and cytotoxicity. FOXP3-overexpressing (Foxp3UP) CD8 T cells exhibited features of tissue-resident memory-like and effector T cells, but not suppressor activity. Transcriptomic analysis of tumor-infiltrating Foxp3UP CD8 T cells showed positive enrichment in a wide variety of metabolic pathways, such as glycolysis, fatty acid (FA) metabolism, and oxidative phosphorylation (OXPHOS). Intratumoral Foxp3UP CD8 T cells exhibited an enhanced capacity for glucose and FA uptake as well as accumulation of intracellular lipids. Interestingly, Foxp3UP CD8 T cells compensated for the loss of mitochondrial respiration-driven ATP production by activating aerobic glycolysis. Moreover, in limiting nutrient conditions these cells engaged FA oxidation to drive OXPHOS for their energy demands. Importantly, their ability to couple glycolysis and OXPHOS allowed them to sustain proliferation under glucose restriction. Our findings demonstrate a hitherto unknown role for FOXP3 in the adaptation of CD8 T cells to TME that may enhance their efficacy in ACT.

Harnessing the small intestinal axis to resolve systemic inflammation

This Perspective presents the potential of the Small Intestinal Axis, a sub-division of the Gut-immune Axis, to modulate systemic inflammation based on sensing contents of the gut lumen. Gut mucosal immunity regulates tolerance to food and gut contents and is a significant factor in maintaining systemic homeostasis without compromising immunity to pathogens. This is achieved through anatomical structures and signaling pathways that link the tolerogenic potential of the proximal small intestine to systemic immunity. Non-live preparations of microbes isolated from human small intestinal mucosa, and the extracellular vesicles (EVs) which they shed, can resolve systemic inflammation without systemic exposure after oral delivery. The mechanism involves primary interactions with pattern recognition receptors followed by trafficking of immune cells through mesenteric lymph nodes. This generates in the periphery a population of circulating CD4+ T cells which have regulatory function but an atypical FoxP3- phenotype. There is no modification of the resident gut microbiome. Discoveries using this novel approach of targeting mucosal microbial elements to the tolerogenic proximal regions of the small intestine are revealing some of the mysteries of the relationship between the gut and immune system.