Differentiation and function of Foxp3+ effector regulatory T cells

Nuclear receptor corepressor 1 controls regulatory T cell subset differentiation and effector function

FOXP3+ regulatory T cells (Treg cells) are key for immune homeostasis. Here, we reveal that nuclear receptor corepressor 1 (NCOR1) controls naïve and effector Treg cell states. Upon NCOR1 deletion in T cells, effector Treg cell frequencies were elevated in mice and in in vitro-generated human Treg cells. NCOR1-deficient Treg cells failed to protect mice from severe weight loss and intestinal inflammation associated with CD4+ T cell transfer colitis, indicating impaired suppressive function. NCOR1 controls the transcriptional integrity of Treg cells, since effector gene signatures were already upregulated in naïve NCOR1-deficient Treg cells while effector NCOR1-deficient Treg cells failed to repress genes associated with naïve Treg cells. Moreover, genes related to cholesterol homeostasis including targets of liver X receptor (LXR) were dysregulated in NCOR1-deficient Treg cells. However, genetic ablation of LXRβ in T cells did not revert the effects of NCOR1 deficiency, indicating that NCOR1 controls naïve and effector Treg cell subset composition independent from its ability to repress LXRβ-induced gene expression. Thus, our study reveals that NCOR1 maintains naïve and effector Treg cell states via regulating their transcriptional integrity. We also reveal a critical role for this epigenetic regulator in supporting the suppressive functions of Treg cells in vivo.

Infiltrating treg reprogramming in the tumor immune microenvironment and its optimization for immunotherapy

Immunotherapy has shown promising anti-tumor effects across various tumors, yet it encounters challenges from the inhibitory tumor immune microenvironment (TIME). Infiltrating regulatory T cells (Tregs) are important contributors to immunosuppressive TIME, limiting tumor immunosurveillance and blocking effective anti-tumor immune responses. Although depletion or inhibition of systemic Tregs enhances the anti-tumor immunity, autoimmune sequelae have diminished expectations for the approach. Herein, we summarize emerging strategies, specifically targeting tumor-infiltrating (TI)-Tregs, that elevate the capacity of organisms to resist tumors by reprogramming their phenotype. The regulatory mechanisms of Treg reprogramming are also discussed as well as how this knowledge could be utilized to develop novel and effective cancer immunotherapies.

Changes in Circulating CD44+CD62L- Treg Subsets and CD44-CD62L+ Treg Subsets Reflect the Clinical Status of Patients with Allergic Rhinitis

INTRODUCTION

This study clarified the expression changes and clinical significance of CD44+CD62L- Treg and CD44-CD62L+ Treg subsets in the peripheral blood of patients with allergic rhinitis (AR).

METHODS

The peripheral blood of 39 patients with AR and 42 healthy controls was collected. Clinical data, such as sex, age, IgE titer, allergen screening information and visual analogue scale (VAS) score, were recorded. Changes in serum IL-2, IL-4, IL-6, IL-10, TNF-α, and IFN-γ were detected using the cytometric bead array method. Flow cytometry was used to detect the proportions of Th1, Th2, Th17, TFH, and Th9 cells and the proportions of CD44+CD62L- Treg and CD44-CD62L+ Treg subsets. Correlation analysis was performed between the CD44+CD62L- Treg subsets and the CD44-CD62L+ Treg subsets with clinical indicators (VAS score, total IgE titer), cytokines (IL-2, IL-4, IL-6, IL-10, TNF-α, IFN-γ), and Th1/Th2/Th17/TFH/Th9 cell proportions.

RESULTS

Compared to the control group, the proportion of total Treg cells and CD44+CD62L- Treg cells in the AR group decreased, and the proportion of CD44-CD62L+ Treg cells increased (p < 0.05). The proportions of CD44+CD62L- Treg cells significantly negatively correlated with Th2 cells (R = -0.5270, p < 0.05) and positively correlated with Treg cytokine IL-10 (R = 0.6447, p < 0.05). In addition, CD44+CD62L- Treg cells negatively correlated with the VAS score (R = -0.4956, p < 0.05), total IgE level (R = -0.4177, p < 0.05) and Th2 cytokine IL-6 level (R = -0.3034, p < 0.05) but positively correlated with the Th1 cytokine IL-2 (R = 0.4331, p < 0.05). In contrast, the proportion of CD44+CD62L- Treg cells significantly positively correlated with the Th2 cells (R = 0.6187, p < 0.05). Moreover, the proportion of CD44-CD62L+ Treg cells positively correlated with the VAS score (R = 0.4060, p < 0.05), total IgE level (R = 0.5224, p < 0.05) and Th2 cytokine IL-4 (R = 0.2647, p < 0.05) and IL-6 levels (R = 0.3824, p < 0.05) but negatively correlated with Th1 cytokine IL-2 (R = -0.3451, p < 0.05) and IL-10 (R = -0.3277, p < 0.05).

CONCLUSION

A greater proportion of CD44+CD62L- Tregs correlated with better reversal of the Th1/Th2 imbalance and milder clinical symptoms in AR patients. The presence of more CD44-CD62L+ Tregs correlated with a weaker immunosuppressive effect on Th2 cells and more severe clinical symptoms in AR patients. These findings provide new perspectives for the treatment and disease monitoring of AR.

Control of Asthma and Allergy by Regulatory T Cells

BACKGROUND

Epithelial barriers, such as the lungs and skin, face the challenge of providing the tissues' physiological function and maintaining tolerance to the commensal microbiome and innocuous environmental factors while defending the host against infectious microbes. Asthma and allergic diseases can result from maladaptive immune responses, resulting in exaggerated and persistent type 2 immunity and tissue inflammation.

SUMMARY

Among the diverse populations of tissue immune cells, CD4+ regulatory T cells (Treg cells) are central to controlling immune responses and inflammation and restoring tissue homeostasis. Humans and mice that are deficient in Treg cells experience extensive inflammation in their mucosal organs and skin. During past decades, major progress has been made toward understanding the immunobiology of Treg cells and the molecular and cellular mechanisms that control their differentiation and function. It is now clear that Treg cells are not a single cell type and that they demonstrate diversity and plasticity depending on their differentiation stages and tissue environment. They could also take on a proinflammatory phenotype in certain conditions.

KEY MESSAGES

Treg cells perform distinct functions, including the induction of immune tolerance, suppression of inflammation, and promotion of tissue repair. Subsets of Treg cells in mucosal tissues are regulated by their differentiation stage and tissue inflammatory milieu. Treg cell dysfunction likely plays roles in persistent immune responses and tissue inflammation in asthma and allergic diseases.

Unraveling the Immune Microenvironment in Diffuse Large B-Cell Lymphoma: Prognostic and Potential Therapeutic Implications

Diffuse large B cell lymphoma (DLBCL) is a multifaceted condition characterized by significant diversity in its molecular and pathological subtypes and clinical manifestation. Despite the progress made in the treatment of DLBCL through the development of novel drugs, an estimated one-third of patients encounter relapse or acquire refractory disease. The tumor microenvironment (TME) of DLBCL, a complex network consisting of cellular and noncellular components that engage in interactions with the tumor, is a parameter that is gaining increasing attention. The TME comprises both the immune and nonimmune microenvironments. The immune microenvironment comprises natural killer (NK) cells, dendritic cells (DCs), tumor-associated macrophages (TAMs), neutrophils, myeloid-derived suppressor cells (MDSCs), and T and B lymphocytes. The nonimmune microenvironment consists of the extracellular matrix (ECM), cancer-associated fibroblasts (CAFs), mesenchymal stromal cells, and other molecules that are secreted. Despite ongoing research, the exact impact of these components and their interaction on the progression of the disease remains elusive. A comprehensive review of significant discoveries concerning the cellular and noncellular constituents, molecular characteristics, and treatment response and prognosis of the TME in DLBCL, as well as the potential targeting of the TME with novel therapeutic approaches, is provided in this article.

CXCR3+ effector regulatory T cells associate with disease tolerance during lower respiratory pneumovirus infection

Lifestyle factors like poor maternal diet or antibiotic exposure disrupt early life microbiome assembly in infants, increasing the risk of severe lower respiratory infections (sLRI). Our prior studies in mice indicated that a maternal low-fibre diet (LFD) exacerbates LRI severity in infants by impairing recruitment of plasmacytoid dendritic cells (pDC) and consequently attenuating expansion of lung regulatory T (Treg) cells during pneumonia virus of mice (PVM) infection. Here, we investigated whether maternal dietary fibre intake influences Treg cell phenotypes in the mediastinal lymph nodes (mLN) and lungs of PVM-infected neonatal mice. Using high dimensional flow cytometry, we identified distinct clusters of regulatory T cells (Treg cells), which differed between lungs and mLN during infection, with notably greater effector Treg cell accumulation in the lungs. Compared to high-fibre diet (HFD)-reared pups, frequencies of various effector Treg cell subsets were decreased in the lungs of LFD-reared pups. Particularly, recruitment of chemokine receptor 3 (CXCR3+) expressing Treg cells was attenuated in LFD-reared pups, correlating with lower lung expression of CXCL9 and CXCL10 chemokines. The recruitment of this subset in response to PVM infection was similarly impaired in pDC depleted mice or following anti-CXCR3 treatment, increasing immunopathology in the lungs. In summary, PVM infection leads to the sequential recruitment and expansion of distinct Treg cell subsets to the lungs and mLN. The attenuated recruitment of the CXCR3+ subset in LFD-reared pups increases LRI severity, suggesting that strategies to enhance pDCs or CXCL9/CXCL10 expression will lower immune-mediated pathogenesis.

High sensitivity of host Helios+/Neuropilin-1+ Treg to pretransplant conditioning hampers development of OX40bright/integrin-β7+ regulatory cells in acute gastrointestinal GvHD

This study sought to compare the behavior of Treg subsets displaying different coexpression patterns of Neuropilin-1 (Nrp1) and Helios, under the influence of gut stress unrelated to hematopoietic stem cell transplantation, pretransplantation conditioning, and posttransplant gastrointestinal acute graft versus host disease (GI-aGvHD). Host CD4+/CD25hi/Foxp3+ Treg cells, identified by flow cytometry, were isolated from various tissues of mice affected by these stressors. Expression of CD25, CTLA-4, CD39, OX40, integrin-β7, LAG3, TGFβ/LAP, granzyme-A, -B, and interleukin-10 was compared in four Treg subsets displaying Helios or Nrp1 only, both or none. Fluorescence-activated cell sorter-sorted Treg subsets, displaying markers affected in a conditioning- and GI-aGVHD-restricted manner, were further investigated by transcriptome profiling and T-cell suppression assays. We found that conditioning by irradiation greatly diminished the relative frequency of Helios+/Nrp1+ Treg, shifting the balance toward Helios-/Nrp1- Treg in the host. Upregulation of integrin-β7 and OX40 occurred in GI-aGvHD-dependent manner in Helios+/Nrp1+ cells but not in Helios-/Nrp1- Treg. Sorted Treg subsets, confirmed to overexpress Nrp1, Helios, OX40, or integrin-β7, displayed superior immunosuppressive activity and enrichment in activation-related messenger RNA transcripts. Our data suggest that conditioning-induced shrinkage of the Nrp1+/Helios+ Treg subset may contribute to the development of GI-GvHD by impairing gut homing and decreasing the efficiency of Treg-mediated immunosuppression.

Roles of IRF4 in various immune cells in systemic lupus erythematosus

Interferon regulatory factor 4 (IRF4) is a member of IRF family of transcription factors which mainly regulates the transcription of IFN. IRF4 is restrictively expressed in immune cells such as T and B cells, macrophages, as well as DC. It is essential for the development and function of these cells. Since these cells take part in the homeostasis of the immune system and dysfunction of them contributes to the initiation and progress of systemic lupus erythematosus (SLE), the roles of IRF4 in the SLE development becomes an important topic. Here we systemically discuss the biological characteristics of IRF4 in various immune cells and analyze the pathologic effects of IRF4 alteration in SLE and the potential targeting therapeutics of SLE.

IKK2 controls the inflammatory potential of tissue-resident regulatory T cells in a murine gain of function model

Loss-of-function mutations have provided crucial insights into the immunoregulatory actions of Foxp3+ regulatory T cells (Tregs). By contrast, we know very little about the consequences of defects that amplify aspects of Treg function or differentiation. Here we show that mice heterozygous for an Ikbkb gain-of-function mutation develop psoriasis. Doubling the gene dose (IkbkbGoF/GoF) results in dactylitis, spondylitis, and characteristic nail changes, which are features of psoriatic arthritis. IkbkbGoF mice exhibit a selective expansion of Foxp3 + CD25+ Tregs of which a subset express IL-17. These modified Tregs are enriched in both inflamed tissues, blood and spleen, and their transfer is sufficient to induce disease without conventional T cells. Single-cell transcriptional and phenotyping analyses of isolated Tregs reveal expansion of non-lymphoid tissue (tissue-resident) Tregs expressing Th17-related genes, Helios, tissue-resident markers including CD103 and CD69, and a prominent NF-κB transcriptome. Thus, IKK2 regulates tissue-resident Treg differentiation, and overactivity drives dose-dependent skin and systemic inflammation.

Insufficient phosphorylation of STAT5 in Tregs inhibits the expression of BLIMP-1 but not IRF4, reduction the proportion of Tregs in pediatric aplastic anemia

Deficiency in regulatory T cells (Tregs) is an important mechanism underlying the pathogenesis of pediatric aplastic anemia, but its specific mechanism is unclear. In our study, we aimed to investigate whether IL-2/STAT5 can regulate the proliferation of Tregs in aplastic anemia (AA) by regulating their expression of B lymphocyte-induced mature protein-1 (BLIMP-1) or interferon regulatory factor 4 (IRF4). Through clinical research and animal experiments, we found that poor activation of the IL-2/STAT5 signaling pathway may leads to low expression of BLIMP-1 in Tregs of children with AA, which leads to defects in the differentiation and proliferation of Tregs in AA. In AA model mice, treatment with IL-2c reversed the decrease in Treg proportions and reduction in Blimp-1 expression in Tregs by increasing the phosphorylation of Stat5 in Tregs. In AA, deficiency of IRF4 expression in Tregs is closely related to the deficiency of Tregs, but is not regulated by the IL-2/STAT5 pathway.

Intragraft memory-like CD127hiCD4+Foxp3+ Tregs maintain transplant tolerance

CD4+Foxp3+ regulatory T cells (Tregs) play an essential role in suppressing transplant rejection, but their role within the graft and heterogeneity in tolerance are poorly understood. Here, we compared phenotypic and transcriptomic characteristics of Treg populations within lymphoid organs and grafts in an islet xenotransplant model of tolerance. We showed Tregs were essential for tolerance induction and maintenance. Tregs demonstrated heterogeneity within the graft and lymphoid organs of tolerant mice. A subpopulation of CD127hi Tregs with memory features were found in lymphoid organs, presented in high proportions within long-surviving islet grafts, and had a transcriptomic and phenotypic profile similar to tissue Tregs. Importantly, these memory-like CD127hi Tregs were better able to prevent rejection by effector T cells, after adoptive transfer into secondary Rag-/- hosts, than naive Tregs or unselected Tregs from tolerant mice. Administration of IL-7 to the CD127hi Treg subset was associated with a strong activation of phosphorylation of STAT5. We proposed that memory-like CD127hi Tregs developed within the draining lymph node and underwent further genetic reprogramming within the graft toward a phenotype that had shared characteristics with other tissue or tumor Tregs. These findings suggested that engineering Tregs with these characteristics either in vivo or for adoptive transfer could enhance transplant tolerance.

Hybrid lineages of CD4+ T cells: a handbook update

CD4+ T lymphocytes have been classified into several lineages, according to their gene expression profiles and their effector responses. Interestingly, recent evidence is showing that many lineages could yield hybrid phenotypes with unique properties and functions. It has been reported that such hybrid lineages might underlie pathologies or may function as effector cells with protection capacities against molecular threats. In this work, we reviewed the characteristics of the hybrid lineages reported in the literature, in order to identify the expression profiles that characterize them and the markers that could be used to identify them. We also review the differentiation cues that elicit their hybrid origin and what is known about their physiological roles.

Turning up the heat: CTLA4 blockade in urothelial cancer

Anti-PD1 and anti-PDL1 monotherapies have shown clinical efficacy in stage IV urothelial cancer and are integrated into current clinical practice. However, only a small number of the patients treated with single-agent checkpoint blockade experience an antitumour response. Insufficient priming or inhibitory factors in the tumour immune microenvironment might have a role in the lack of response. CTLA4 is an inhibitory checkpoint on activated T cells that is being studied as a therapeutic target in combination with anti-PD1 or anti-PDL1 therapies in advanced urothelial cancer. In locally advanced urothelial cancer, this combination approach has shown encouraging antitumour effects when administered pre-operatively. We believe that the presence of pre-existing intratumoural T cell immunity is not a prerequisite for response to combination therapy and that the additional value of CTLA4 blockade might involve the broadening of peripheral T cell priming, thereby transforming immunologically cold tumours into hot tumours.

Selective IL-27 production by intestinal regulatory T cells permits gut-specific regulation of TH17 cell immunity

Regulatory T cells (Treg cells) are instrumental in establishing immunological tolerance. However, the precise effector mechanisms by which Treg cells control a specific type of immune response in a given tissue remains unresolved. By simultaneously studying Treg cells from different tissue origins under systemic autoimmunity, in the present study we show that interleukin (IL)-27 is specifically produced by intestinal Treg cells to regulate helper T17 cell (TH17 cell) immunity. Selectively increased intestinal TH17 cell responses in mice with Treg cell-specific IL-27 ablation led to exacerbated intestinal inflammation and colitis-associated cancer, but also helped protect against enteric bacterial infection. Furthermore, single-cell transcriptomic analysis has identified a CD83+CD62Llo Treg cell subset that is distinct from previously characterized intestinal Treg cell populations as the main IL-27 producers. Collectively, our study uncovers a new Treg cell suppression mechanism crucial for controlling a specific type of immune response in a particular tissue and provides further mechanistic insights into tissue-specific Treg cell-mediated immune regulation.

An essential role for miR-15/16 in Treg suppression and restriction of proliferation

The miR-15/16 family targets a large network of genes in T cells to restrict their cell cycle, memory formation, and survival. Upon T cell activation, miR-15/16 are downregulated, allowing rapid expansion of differentiated effector T cells to mediate a sustained response. Here, we used conditional deletion of miR-15/16 in regulatory T cells (Tregs) to identify immune functions of the miR-15/16 family in T cells. miR-15/16 are indispensable to maintain peripheral tolerance by securing efficient suppression by a limited number of Tregs. miR-15/16 deficiency alters expression of critical Treg proteins and results in accumulation of functionally impaired FOXP3loCD25loCD127hi Tregs. Excessive proliferation in the absence of miR-15/16 shifts Treg fate and produces an effector Treg phenotype. These Tregs fail to control immune activation, leading to spontaneous multi-organ inflammation and increased allergic inflammation in a mouse model of asthma. Together, our results demonstrate that miR-15/16 expression in Tregs is essential to maintain immune tolerance.

Construction and validation of a metabolism-associated gene signature for predicting the prognosis, immune landscape, and drug sensitivity in bladder cancer

Tumor Metabolism is strongly correlated with prognosis. Nevertheless, the prognostic and therapeutic value of metabolic-associated genes in BCa patients has not been fully elucidated. First, in this study, metabolism-related differential expressed genes DEGs with prognostic value in BCa were determined. Through the consensus clustering algorithm, we identified two molecular clusters with significantly different clinicopathological features and survival prognosis. Next, a novel metabolism-related prognostic model was established. Its reliable predictive performance in BCa was verified by multiple external datasets. Multivariate Cox analysis exhibited that risk score were independent prognostic factors. Interestingly, GSEA enrichment analysis of GO, KEGG, and Hallmark gene sets showed that the biological processes and pathways associated with ECM and collagen binding in the high-risk group were significantly enriched. Notely, the model was also significantly correlated with drug sensitivity, immune cell infiltration, and immunotherapy efficacy prediction by the wilcox rank test and chi-square test. Based on the 7 immune infiltration algorithm, we found that Neutrophils, Myeloid dendritic cells, M2 macrophages, Cancer-associated fibroblasts, etc., were more concentrated in the high-risk group. Additionally, in the IMvigor210, GSE111636, GSE176307, or our Truce01 (registration number NCT04730219) cohorts, the expression levels of multiple model genes were significantly correlated with objective responses to anti-PD-1/anti-PD-L1 immunotherapy. Finally, the expression of interested model genes were verified in 10 pairs of BCa tissues and para-carcinoma tissues by the HPA and real-time fluorescent quantitative PCR. Altogether, the signature established and validated by us has high predictive power for the prognosis, immunotherapy responsiveness, and chemotherapy sensitivity of BCa.

Zfp335 establishes eTreg lineage and neonatal immune tolerance by targeting Hadha-mediated fatty acid oxidation

Regulatory T cells (Tregs) are instrumental in maintaining immune tolerance and preventing destructive autoimmunity, but how heterogeneous Treg populations are established remains largely unknown. Here, we show that Zfp335 deletion in Tregs failed to differentiate into effector Tregs (eTregs) and lose Treg-suppressive function and that KO mice exhibited early-onset lethal autoimmune inflammation with unrestricted activation of conventional T cells. Single-cell RNA-Seq analyses revealed that Zfp335-deficient Tregs lacked a eTreg population and showed dramatic accumulation of a dysfunctional Treg subset. Mechanistically, Zfp335-deficient Tregs displayed reduced oxidative phosphorylation and dysfunctional mitochondrial activity. Further studies revealed that Zfp335 controlled eTreg differentiation by regulating fatty acid oxidation (FAO) through direct targeting of the FAO enzyme Hadha. Importantly, we demonstrate a positive correlation between ZNF335 and HADHA expression in human eTregs. Our findings reveal that Zfp335 controls FAO-driven eTreg differentiation to establish immune tolerance.

BATF is Required for Treg Homeostasis and Stability to Prevent Autoimmune Pathology

Regulatory T (Treg) cells are inevitable to prevent deleterious immune responses to self and commensal microorganisms. Treg function requires continuous expression of the transcription factor (TF) FOXP3 and is divided into two major subsets: resting (rTregs) and activated (aTregs). Continuous T cell receptor (TCR) signaling plays a vital role in the differentiation of aTregs from their resting state, and in their immune homeostasis. The process by which Tregs differentiate, adapt tissue specificity, and maintain stable phenotypic expression at the transcriptional level is still inconclusivei. In this work, the role of BATF is investigated, which is induced in response to TCR stimulation in naïve T cells and during aTreg differentiation. Mice lacking BATF in Tregs developed multiorgan autoimmune pathology. As a transcriptional regulator, BATF is required for Treg differentiation, homeostasis, and stabilization of FOXP3 expression in different lymphoid and non-lymphoid tissues. Epigenetically, BATF showed direct regulation of Treg-specific genes involved in differentiation, maturation, and tissue accumulation. Most importantly, FOXP3 expression and Treg stability require continuous BATF expression in Tregs, as it regulates demethylation and accessibility of the CNS2 region of the Foxp3 locus. Considering its role in Treg stability, BATF should be considered an important therapeutic target in autoimmune disease.

IL-2-induced Stat3 Signaling is Critical for Effector Treg Cell Programming

Maintenance of immune homeostasis to the intestinal mictrobiota is dependent on a population of effector regulatory T (eTreg) cells that develop from microbiota-reactive induced (i)Treg cells. A cardinal feature of eTreg cells is their production of IL-10, which plays a non-redundant role in immune tolerance of commensal microbes. Here, we identify an unexpected role for IL-2-induced Stat3 signaling to program iTreg cells for eTreg cell differentiation and Il10 transcriptional competency. IL-2 proved to be both necessary and sufficient for eTreg cell development - contingent on Stat3 output of the IL-2 receptor coordinate with IL-2 signaling during early Treg cell commitment. Induction of iTreg cell programming in absence of IL-2-induced Stat3 signaling resulted in impaired eTreg cell differentiation and a failure to produce IL-10. An IL-2 mutein with reduced affinity for the IL-2Rγ (γ c ) chain was found to have blunted IL-2R Stat3 output, resulting in a deficiency of Il10 transcriptional programming that could not be fully rescued by Stat3 signaling subsequent to an initial window of iTreg cell differentiation. These findings expose a heretofore unappreciated role of IL-2 signaling that acts early to program subsequent production of IL-10 by developing eTreg cells, with broad implications for IL-2-based therapeutic interventions in immune-mediated diseases.

The functional adaptation of effector Foxp3+ regulatory T cells to pulmonary inflammation

During infections, the timings of effector differentiation of pulmonary immune responses are of paramount importance, as pathogen persistence and unsuppressed inflammation can rapidly lead to a loss of function, increased frailty, and death. Thus, both an efficient clearance of the danger and a rapid resolution of inflammation are critical to host survival. We now know that tissue-localized FoxP3+ regulatory T cells, a subset of CD4+ T cells, are highly attuned to the type of immune response, acquiring unique phenotypic characteristics that allow them to adapt their suppressive functions with the nature of inflammatory cells. To achieve this, activated effector TREG cells acquire specialized TH 1, TH 2, and TH 17-like characteristics that allow them to migrate, survive, and time their function(s) through refined mechanisms. Herein, we describe how this process requires a unique developmental path that includes the acquisition of master transcription factors and the expression of receptors adapted to sense local danger signals that are found during pulmonary inflammation. In turn, we offer an overview of how these characteristics promote the capacity of local effector TREG cells to proliferate, survive, and display suppressive strategies to resolve lung injury.

CXCR3 expression in regulatory T cells drives interactions with type I dendritic cells in tumors to restrict CD8+ T cell antitumor immunity

Infiltration of regulatory T (Treg) cells, an immunosuppressive population of CD4+ T cells, into solid cancers represents a barrier to cancer immunotherapy. Chemokine receptors are critical for Treg cell recruitment and cell-cell interactions in inflamed tissues, including cancer, and thus are an ideal therapeutic target. Here, we show in multiple cancer models that CXCR3+ Treg cells were increased in tumors compared with lymphoid tissues, exhibited an activated phenotype, and interacted preferentially with CXCL9-producing BATF3+ dendritic cells (DCs). Genetic ablation of CXCR3 in Treg cells disrupted DC1-Treg cell interactions and concomitantly increased DC-CD8+ T cell interactions. Mechanistically, CXCR3 ablation in Treg cells increased tumor antigen-specific cross-presentation by DC1s, increasing CD8+ T cell priming and reactivation in tumors. This ultimately impaired tumor progression, especially in combination with anti-PD-1 checkpoint blockade immunotherapy. Overall, CXCR3 is shown to be a critical chemokine receptor for Treg cell accumulation and immune suppression in tumors.

Nanomaterials for antigen-specific immune tolerance therapy

Impairment of immune tolerance might cause autologous tissue damage or overactive immune response against non-pathogenic molecules. Although autoimmune disease and allergy have complicated pathologies, the current strategies have mainly focused on symptom amelioration or systemic immunosuppression which can lead to fatal adverse events. The induction of antigen-specific immune tolerance may provide therapeutic benefits to autoimmune disease and allergic response, while reducing nonspecific immune adverse responses. Diverse nanomaterials have been studied to induce antigen-specific immune tolerance therapy. This review will cover the immunological background of antigen-specific tolerance, clinical importance of antigen-specific immune tolerance, and nanomaterials designed for autoimmune and allergic diseases. As nanomaterials for modulating immune tolerances, lipid-based nanoparticles, polymeric nanoparticles, and biological carriers have been covered. Strategies to provide antigen-specific immune tolerance have been addressed. Finally, current challenges and perspectives of nanomaterials for antigen-specific immune tolerance therapy will be discussed.

Relationship between systemic inflammation and lung injury induced by chromate exposure: A cross-sectional study in workers

Hexavalent chromium [Cr(VI)] compounds, known as "Group I Human Carcinogen" and "Category I Respiratory Sensitizer", posed great challenges to the respiratory system. A cross-sectional study was undertaken among chromate workers. Serum club cell protein 16 (CC16) and soluble urokinase-type plasminogen activator receptor (suPAR) were measured using ELISA. Thirteen macrophage-related mediators were tested using cytometric bead array. After controlling for sex, age, smoking status, drinking status and BMI, each increase of one-unit of Ln-transformed blood Cr was related to the increase of IL-1beta [Beta (95% CI), 7.22(1.14, 13.29)%, P = 0.021], IL-23 [8.5(1.15, 15.85)%, P = 0.021], IFN-gamma [3.14(0.15, 6.13)%, P = 0.040], and suPAR [9.31(2.5, 16.12) %, P = 0.008], as well as the increase of CC16 by 3.88(0.42, 7.34) % (P = 0.029). Moreover, these inflammatory mediators played an mediation role in the rise of CC16 caused by Cr(VI). The exposure-response curve analysis revealed a substantial nonlinear association of IFN-gamma and suPAR with CC16, thus the mediation effect of INF-gamma and suPAR required cautious interpretation. The positive connection between macrophage-related mediators was stronger in the high exposure group than in the low exposure group, suggesting that high concentration of chromate might promote a complex interplay within the immune system.

Unraveling the Immune Microenvironment in Classic Hodgkin Lymphoma: Prognostic and Therapeutic Implications

Classic Hodgkin lymphoma (cHL) is a lymphoid neoplasm composed of rare neoplastic Hodgkin and Reed-Sternberg (HRS) cells surrounded by a reactive tumor microenvironment (TME) with suppressive properties against anti-tumor immunity. TME is mainly composed of T cells (CD4 helper, CD8 cytotoxic and regulatory) and tumor-associated macrophages (TAMs), but the impact of these cells on the natural course of the disease is not absolutely understood. TME contributes to the immune evasion of neoplastic HRS cells through the production of various cytokines and/or the aberrant expression of immune checkpoint molecules in ways that have not been fully understood yet. Herein, we present a comprehensive review of findings regarding the cellular components and the molecular features of the immune TME in cHL, its correlation with treatment response and prognosis, as well as the potential targeting of the TME with novel therapies. Among all cells, macrophages appear to be a most appealing target for immunomodulatory therapies, based on their functional plasticity and antitumor potency.

Microbiota-assisted iron uptake promotes immune tolerance in the intestine

Iron deficiencies are the most common nonenteric syndromes observed in patients with inflammatory bowel disease, but little is known about their impacts on immune tolerance. Here we show that homeostasis of regulatory T cells in the intestine was dependent on high cellular iron levels, which were fostered by pentanoate, a short-chain fatty acid produced by intestinal microbiota. Iron deficiencies in Treg caused by the depletion of Transferrin receptor 1, a major iron transporter, result in the abrogation of Treg in the intestine and lethal autoimmune disease. Transferrin receptor 1 is required for differentiation of c-Maf+ Treg, major constituents of intestinal Treg. Mechanistically, iron enhances the translation of HIF-2α mRNA, and HIF-2α in turn induces c-Maf expression. Importantly, microbiota-produced pentanoate promotes iron uptake and Treg differentiation in the intestine. This subsequently restores immune tolerance and ameliorated iron deficiencies in mice with colitis. Our results thus reveal an association between nutrient uptake and immune tolerance in the intestine.

Immunoprofiling bronchoalveolar lavage cells reveals multifaceted smoking-associated immune dysfunction

Background

Bronchoalveolar lavage (BAL) is an underutilised tool in the search for pulmonary disease biomarkers. While leukocytes with effector and suppressor function play important roles in airway immunity and tumours, it remains unclear if frequencies and phenotypes of BAL leukocytes can be useful parameters in lung cancer studies and clinical trials. We therefore explored the utility of BAL leukocytes as a source of biomarkers interrogating the impact of smoking, a major lung cancer risk determinant, on pulmonary immunity.

Methods

In this "test case" observational study, BAL samples from 119 donors undergoing lung cancer screening and biopsy procedures were evaluated by conventional and spectral flow cytometry to exemplify the comprehensive immune analyses possible with this biospecimen. Proportions of major leukocyte populations and phenotypic markers levels were found. Multivariate linear rank sum analysis considering age, sex, cancer diagnosis and smoking status was performed.

Results

Significantly increased frequencies of myeloid-derived suppressor cells and PD-L1-expressing macrophages were found in current and former smokers compared to never-smokers. While cytotoxic CD8 T-cells and conventional CD4 helper T-cell frequencies were significantly reduced in current and former smokers, expression of immune checkpoints PD-1 and LAG-3 as well as Tregs proportions were increased. Lastly, the cellularity, viability and stability of several immune readouts under cryostorage suggested BAL samples are useful for correlative end-points in clinical trials.

Conclusions

Smoking is associated with heightened markers of immune dysfunction, readily assayable in BAL, that may reflect a permissive environment for cancer development and progression in the airway.

Parallel recovery of chromatin accessibility and gene expression dynamics from frozen human regulatory T cells

Epigenetic features such as DNA accessibility dictate transcriptional regulation in a cell type- and cell state- specific manner, and mapping this in health vs. disease in clinically relevant material is opening the door to new mechanistic insights and new targets for therapy. Assay for Transposase Accessible Chromatin Sequencing (ATAC-seq) allows chromatin accessibility profiling from low cell input, making it tractable on rare cell populations, such as regulatory T (Treg) cells. However, little is known about the compatibility of the assay with cryopreserved rare cell populations. Here we demonstrate the robustness of an ATAC-seq protocol comparing primary Treg cells recovered from fresh or cryopreserved PBMC samples, in the steady state and in response to stimulation. We extend this method to explore the feasibility of conducting simultaneous quantitation of chromatin accessibility and transcriptome from a single aliquot of 50,000 cryopreserved Treg cells. Profiling of chromatin accessibility and gene expression in parallel within the same pool of cells controls for cellular heterogeneity and is particularly beneficial when constrained by limited input material. Overall, we observed a high correlation of accessibility patterns and transcription factor dynamics between fresh and cryopreserved samples. Furthermore, highly similar transcriptomic profiles were obtained from whole cells and from the supernatants recovered from ATAC-seq reactions. We highlight the feasibility of applying these techniques to profile the epigenomic landscape of cells recovered from cryopreservation biorepositories.

An essential role for miR-15/16 in Treg suppression and restriction of proliferation

The miR-15/16 family is a highly expressed group of tumor suppressor miRNAs that target a large network of genes in T cells to restrict their cell cycle, memory formation and survival. Upon T cell activation, miR-15/16 are downregulated, allowing rapid expansion of differentiated effector T cells to mediate a sustained immune response. Here, using conditional deletion of miR-15/16 in immunosuppressive regulatory T cells (Tregs) that express FOXP3, we identify new functions of the miR-15/16 family in T cell immunity. miR-15/16 are indispensable to maintain peripheral tolerance by securing efficient suppression by a limited number of Tregs. miR-15/16-deficiency alters Treg expression of critical functional proteins including FOXP3, IL2Rα/CD25, CTLA4, PD-1 and IL7Rα/CD127, and results in accumulation of functionally impaired FOXP3loCD25loCD127hi Tregs. Excessive proliferation in the absence of miR-15/16 inhibition of cell cycle programs shifts Treg diversity and produces an effector Treg phenotype characterized by low expression of TCF1, CD25 and CD62L, and high expression of CD44. These Tregs fail to control immune activation of CD4+ effector T cells, leading to spontaneous multi-organ inflammation and increased allergic airway inflammation in a mouse model of asthma. Together, our results demonstrate that miR-15/16 expression in Tregs is essential to maintain immune tolerance.

Selective IL-27 production by intestinal regulatory T cells permits gut-specific regulation of Th17 immunity

Regulatory T (Treg) cells are instrumental in establishing immunological tolerance. However, the precise effector mechanisms by which Treg cells control a specific type of immune response in a given tissue remains unresolved. By simultaneously studying Treg cells from different tissue origins under systemic autoimmunity, here we show that IL-27 is specifically produced by intestinal Treg cells to regulate Th17 immunity. Selectively increased intestinal Th17 responses in mice with Treg cell-specific IL-27 ablation led to exacerbated intestinal inflammation and colitis-associated cancer, but also helped protect against enteric bacterial infection. Furthermore, single-cell transcriptomic analysis has identified a CD83+TCF1+ Treg cell subset that is distinct from previously characterized intestinal Treg cell populations as the main IL-27 producers. Collectively, our study uncovers a novel Treg cell suppression mechanism crucial for controlling a specific type of immune response in a particular tissue, and provides further mechanistic insights into tissue-specific Treg cell-mediated immune regulation.

Fasting Protocols Do Not Improve Intestinal Architecture and Immune Parameters in C57BL/6 Male Mice Fed a High Fat Diet

BACKGROUND

The intestinal ecosystem, including epithelium, immune cells, and microbiota, are influenced by diet and timing of food consumption. The purpose of this study was to evaluate various dietary protocols after ad libitum high fat diet (HFD) consumption on intestinal morphology and mucosal immunity.

METHODS

C57BL/6 male mice were fed a 45% high fat diet (HFD) for 6 weeks and then randomized to the following protocols; (1) chow, (2) a purified high fiber diet known as the Daniel Fast (DF), HFD consumed (3) ad libitum or in a restricted manner; (4) caloric-restricted, (5) time-restricted (six hours of fasting in each 24 h), or (6) alternate-day fasting (24 h fasting every other day). Intestinal morphology and gut-associated immune parameters were investigated after 2 months on respective protocols.

RESULTS

Consuming a HFD resulted in shortening of the intestine and reduction in villi and crypt size. Fasting, while consuming the HFD, did not restore these parameters to the extent seen with the chow and DF diet. Goblet cell number and regulatory T cells had improved recovery with high fiber diets, not seen with the HFD irrespective of fasting.

CONCLUSION

Nutritional content is a critical determinant of intestinal parameters associated with gut health.

Treg-selective IL-2 starvation synergizes with CD40 activation to sustain durable responses in lymphoma models

BACKGROUND

Roughly half of all diffuse large B-cell lymphomas (DLBCLs) are infiltrated by large numbers of regulatory T-cells (Tregs). Although the presence of 'effector' Tregs in particular is associated with an inferior prognosis in patients on standard rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) immunochemotherapy, the role of this cell type during lymphoma initiation and progression is poorly understood.

METHODS

Here, we use tissue microarrays containing prospectively collected DLBCL patient specimens, as well as data from publicly available cohorts to explore the mutational landscape of Treg-infiltrated DLBCL. We further take advantage of a model of MYC-driven lymphoma to mechanistically dissect the contribution of Tregs to lymphoma pathogenesis and to develop a strategy of Treg-selective interleukin-2 (IL-2) starvation to improve immune control of MYC-driven lymphoma.

RESULTS

We find that all genetic DLBCL subtypes, except for one characterized by co-occurring MYD88/CD79 mutations, are heavily infiltrated by Tregs. Spectral flow cytometry and scRNA-sequencing reveal the robust expression of functional and immunosuppressive markers on Tregs infiltrating MYC-driven lymphomas; notably, we find that intratumoral Tregs arise due to local conversion from naïve CD4+ precursors on tumor contact. Treg ablation in Foxp3iDTR mice, or by antibody-mediated Treg-selective blockade of IL-2 signaling, strongly reduces the lymphoma burden. We identify lymphoma B-cells as a major source of IL-2, and show that the effects of Treg depletion are reversed by the simultaneous depletion of Foxp3-negative CD4+ T-cells, but not CD8+ T-cells or natural killer (NK) cells. The inhibition of ATP hydrolyzation and adenosine production by Tregs at least partly phenocopies the effects of Treg depletion. Treg depletion further synergizes with pro-apoptotic CD40 activation to sustain durable responses.

CONCLUSION

The combined data implicate Tregs as a potential therapeutic target in DLBCL, especially in combination with other immunotherapies.

Regulatory T cell homeostasis: Requisite signals and implications for clinical development of biologics

Novel biologics are currently being tested in clinical trials for the treatment of autoimmune diseases and the prevention of transplant allograft rejection. Their premise is to deliver highly efficient immunosuppression while minimizing side-effects, as they specifically target inflammatory mediators involved in the dysregulation of the immune system. However, the pleiotropism of soluble mediators and cell-to-cell interactions with potential to exert both proinflammatory and regulatory influences on the outcome of the immune response can lead to unpredictable results. Predicting responses to biologic drugs requires mechanistic understanding of the cell type-specific effect of immune mediators. Elucidation of the central role of regulatory T cells (Treg), a small subset of T cells dedicated to immune homeostasis, in preventing the development of auto- and allo-immunity has provided a deeper understanding of the signaling pathways that govern immune tolerance. This review focuses on the requisite signals that promote Treg homeostasis and discusses the anticipated outcomes of biologics targeting these signals. Our goal is to inform and facilitate the design of cell-specific biologics that thwart T effector cells (Teff) while promoting Treg function for the treatment of autoimmune diseases and the prevention of transplant rejection.

Setd2 supports GATA3+ST2+ thymic-derived Treg cells and suppresses intestinal inflammation

Treg cells acquire distinct transcriptional properties to suppress specific inflammatory responses. Transcription characteristics of Treg cells are regulated by epigenetic modifications, the mechanism of which remains obscure. Here, we report that Setd2, a histone H3K36 methyltransferase, is important for the survival and suppressive function of Treg cells, especially those from the intestine. Setd2 supports GATA3⁺ST2⁺ intestinal thymic-derived Treg (tTreg) cells by facilitating the expression and reciprocal relationship of GATA3 and ST2 in tTreg cells. IL-33 preferentially boosts Th2 cells rather than GATA3⁺ Treg cells in Foxp3^Cre-YFPSetd2 ^flox/flox mice, corroborating the constraint of Th2 responses by Setd2 expression in Treg cells. SETD2 sustains GATA3 expression in human Treg cells, and SETD2 expression is increased in Treg cells from human colorectal cancer tissues. Epigenetically, Setd2 regulates the transcription of target genes (including Il1rl1) by modulating the activity of promoters and intragenic enhancers where H3K36me3 is typically deposited. Our findings provide mechanistic insights into the regulation of Treg cells and intestinal immunity by Setd2.

Regulatory T Cells Require CCR6 for Skin Migration and Local Suppression of Vitiligo

Vitiligo is an autoimmune skin disease caused by melanocyte-targeting autoreactive CD8+ T cells. Regulatory T cells (Tregs) have been implicated in restraining vitiligo severity in both mouse models and human patients; however, whether they must be present in the skin for their suppressive function is still unclear. We observed uneven distribution of Tregs within different anatomical locations of mouse skin, which correlated with reduced depigmentation after vitiligo induction. We specifically depleted Tregs in our mouse model of vitiligo and observed increased disease. Next, we found that Tregs contact CD8+ T effector cells in vitiligo lesional skin and that Treg recruitment to the skin inversely correlated with disease severity, suggesting a critical role for Treg suppression within the skin. When we investigated the signals facilitating Treg migration to the skin, we found that although CXCR3 was dispensable for Treg migration and function in vitiligo, Tregs lacking CCR6 exhibited a reduced capacity to migrate to the skin and suppress depigmentation, despite normal systemic numbers in the skin-draining lymph nodes. Our observations highlight a key role for cutaneous Tregs in disease suppression during vitiligo and identify CCR6 as a chemokine receptor that contributes to Treg migration to the skin.

The frequency of Treg subsets distinguishes disease activity in ANCA vasculitis

Objectives

T regulatory cells (Tregs) are a heterogeneous group of immunoregulatory cells that dampen self-harming immune responses and prevent the development of autoimmune diseases. In anti-neutrophil cytoplasmic autoantibody (ANCA) vasculitis, Tregs possess diminished suppressive capacity, which has been attributed to the expression of a FOXP3 splice-variant lacking exon 2 in T cells (FOXP3Δ2 CD4+ T cells). However, the suppressive capacity of Tregs varies between subsets. We evaluated the frequency of Treg subsets in ANCA vasculitis as a potential explanation for diminished suppressive capacity.

Methods

We developed a custom mass cytometry panel and performed deep immune profiling of Tregs in healthy controls, patients with active disease and in remission. Using these data, we performed multidimensional reduction and discriminant analysis to identify associations between Treg subsets and disease activity.

Results

Total Tregs were expanded in ANCA vasculitis, which was associated with remission and the administration of rituximab and/or prednisone. The frequency of FOXP3Δ2 CD4+ T cells did not distinguish disease activity and this population had high expression levels of CD127 and lacked both CD25 and Helios, suggesting that they are not conventional Tregs. The frequency of CXCR3+, CD103+ and CCR7+ Tregs distinguished disease activity, and the combination of the frequency of these three Treg subsets segregated active patients from patients in remission and healthy controls. From these three subsets, the frequency of CXCR3+ Tregs distinguished patients with active disease with renal involvement.

Conclusion

Treg heterogeneity can discriminate disease activity and should be explored as a biomarker of disease activity in ANCA vasculitis.

(Not) Home alone: Antigen presenting cell - T Cell communication in barrier tissues

Priming of T cells by antigen presenting cells (APCs) is essential for T cell fate decisions, enabling T cells to migrate to specific tissues to exert their effector functions. Previously, these interactions were mainly explored using blood-derived cells or animal models. With great advances in single cell RNA-sequencing techniques enabling analysis of tissue-derived cells, it has become clear that subsets of APCs are responsible for priming and modulating heterogeneous T cell effector responses in different tissues. This composition of APCs and T cells in tissues is essential for maintaining homeostasis and is known to be skewed in infection and inflammation, leading to pathological T cell responses. This review highlights the commonalities and differences of T cell priming and subsequent effector function in multiple barrier tissues such as the skin, intestine and female reproductive tract. Further, we provide an overview of how this process is altered during tissue-specific infections which are known to cause chronic inflammation and how this knowledge could be harnessed to modify T cell responses in barrier tissue.

PD-1 and ICOS counter-regulate tissue resident regulatory T cell development and IL-10 production during flu

Regulatory T cells that express the transcription factor Foxp3 (Treg cells) are a highly heterogenous population of immunoregulatory cells critical for maintaining immune homeostasis and preventing immunopathology during infections. Tissue resident Treg (TR-Treg) cells are maintained within nonlymphoid tissues and have been shown to suppress proinflammatory tissue resident T cell responses and promote tissue repair. Human populations are repetitively exposed to influenza infections and lung tissue resident effector T cell responses are associated with flu-induced long-term pulmonary sequelae. The kinetics of TR-Treg cell development and molecular features of TR-Treg cells during repeated and/or long-term flu infections are unclear. Utilizing a Foxp3^RFP/IL-10^GFP dual reporter mouse model along with intravascular fluorescent in vivo labeling, we characterized the TR-Treg cell responses to repetitive heterosubtypic influenza infections. We found lung tissue resident Treg cells accumulated and expressed high levels of co-inhibitory and co-stimulatory receptors post primary and secondary infections. Blockade of PD-1 or ICOS signaling reveals that PD-1 and ICOS signaling pathways counter-regulate TR-Treg cell expansion and IL-10 production, during secondary influenza infection. Furthermore, the virus-specific TR-Treg cell response displayed distinct kinetics, when compared to conventional CD4⁺ tissue resident memory T cells, during secondary flu infection. Our results provide insight into the tissue resident Foxp3⁺ regulatory T cell response during repetitive flu infections, which may be applicable to other respiratory infectious diseases such as tuberculosis and COVID.

Migration and homeostasis of regulatory T cells in rheumatoid arthritis

Regulatory T (T_reg) cells are garnering increased attention in research related to autoimmune diseases, including rheumatoid arthritis (RA). They play an essential role in the maintenance of immune homeostasis by restricting effector T cell activity. Reduced functions and frequencies of T_reg cells contribute to the pathogenesis of RA, a common autoimmune disease which leads to systemic inflammation and erosive joint destruction. T_reg cells from patients with RA are characterized by impaired functions and by an altered phenotype. They show increased plasticity towards Th17 cells and a reduced suppressive capacity. Besides the suppressive function of T_reg cells, their effectiveness is determined by their ability to migrate into inflamed tissues. In the past years, new mechanisms involved in T_reg cell migration have been identified. One example of such a mechanism is the phosphorylation of vasodilator-stimulated phosphoprotein (VASP). Efficient migration of T_reg cells requires the presence of VASP. IL-6, a cytokine which is abundantly present in the peripheral blood and in the synovial tissue of RA patients, induces posttranslational modifications of VASP. Recently, it has been shown in mice with collagen-induced arthritis (CIA) that this IL-6 mediated posttranslational modification leads to reduced T_reg cell trafficking. Another protein which facilitates T_reg cell migration is G-protein-signaling modulator 2 (GPSM2). It modulates G-protein coupled receptor functioning, thereby altering the cellular activity initiated by cell surface receptors in response to extracellular signals. The almost complete lack of GPSM2 in T_reg cells from RA patients contributes to their reduced ability to migrate towards inflammatory sites. In this review article, we highlight the newly identified mechanisms of T_reg cell migration and review the current knowledge about impaired T_reg cell homeostasis in RA.

BACH2 in TRegs Limits the Number of Adipose Tissue Regulatory T Cells and Restrains Type 2 Immunity to Fungal Allergens

FoxP3+ regulatory T cells (Tregs) are essential for self-tolerance and moderating tissue-damaging inflammation. Tregs that develop and mature in the thymus are classified as central Tregs or effector Tregs based on whether Tregs predominately inhabit secondary lymphoid organs (central Tregs) or tissues (effector Tregs). By generating mice that are conditionally deficient for Bach2 in peripheral Tregs, we have examined the role of Bach2 in regulating Treg homeostasis and effector functions. Unlike global and T cell-specific Bach2-deficient mice, Treg-specific Bach2 ablation did not result in unprovoked TH2 inflammation in the lungs. However, Bach2 deficiency in Tregs led to augmented expressions of IRF4, BATF, and GATA3 and a significant increase in the accumulation of ST2 (IL-33R)+ve effector Tregs in the spleen and visceral adipose tissue (VAT) but not in the lungs. Enhanced Bach2-deficient Treg numbers in VAT was not linked to hyperresponsiveness to exogenous IL-33 in vivo. Most strikingly, Treg-specific Bach2 deficiency resulted in enhanced fungal protease-induced Type 2 allergic inflammation in the lungs, with no detectable effects on Type 1 responses to systemic or respiratory viral infections. In summary, we ascribe vital roles for Bach2 in peripheral Tregs: as a transcriptional checkpoint to limit precocious differentiation into effector Tregs in lymphoid tissues and as a regulator of the functional program that restrains Type 2 but not Type 1 inflammation in lungs. Results presented in this manuscript implicate dysregulated Tregs in the pathogenesis of airway hypersensitivities, asthma, and other allergic disorders.

Implications of regulatory T cells in non-lymphoid tissue physiology and pathophysiology

Treg cells have been initially described as gatekeepers for the control of autoimmunity, as they can actively suppress the activity of other immune cells. However, their role goes beyond this as Treg cells further control immune responses during infections and tumor development. Furthermore, Treg cells can acquire additional properties for e.g., the control of tissue homeostasis. This is instructed by a specific differentiation program and the acquisition of effector properties unique to Treg cells in non-lymphoid tissues. These tissue Treg cells can further adapt to their tissue environment and acquire distinct functional properties through specific transcription factors activated by a combination of tissue derived factors, including tissue-specific antigens and cytokines. In this review, we will focus on recent findings extending our current understanding of the role and differentiation of these tissue Treg cells. As such we will highlight the importance of tissue Treg cells for tissue maintenance, regeneration, and repair in adipose tissue, muscle, CNS, liver, kidney, reproductive organs, and the lung.

Interleukin-37, vascular endothelial growth factor A, and transforming growth factor-β1: promising biomarkers in primary immune thrombocytopenia

BACKGROUND

Immune thrombocytopenic purpura (ITP) is an acquired autoimmune hematologic disorder with heterogeneous bleeding manifestations. Many biomarkers such as interleukin-37 (IL-37), vascular endothelial growth factor A (VEGFA), and transforming growth factor-β1 (TGFß1) have a role in immunity, inflammation, and megakaryopoiesis.

METHODS

In the present study, immunoassay of interleukin-37 as well as the gene expression of vascular endothelial growth factor A and transforming growth factor-β1 were done in 60 primary ITP patients, 60 thrombocytopenia patients, and 60 healthy volunteers.

RESULTS

Increased IL-37 level and down regulation of VEGFA and TGFß1gene expression were detected in primary ITP patients when compared with other groups. A negative correlation was observed between IL-37 and platelet count. However, a positive correlation was observed between VEGFA and TGFß1 levels and platelet count.

CONCLUSION

Current results suggested that interleukin-37, vascular endothelial growth factor A, and transforming growth factor-β may be promising indicators in the diagnosis of ITP and detection of disease severity with inexpensive and cost-effectiveness compared to the benefits.

Enhancing and stabilization of cord blood regulatory T-cell suppressive function by human mesenchymal stem cell (MSC)-derived exosomes

FOXP3+ regulatory T cells (Tregs) are central to maintaining peripheral tolerance and immune homeostasis. They have the potential to be developed as a cellular therapy to treat various clinical ailments such as autoimmune disorders, inflammatory diseases and to improve transplantation outcomes. However, a major question remains whether Tregs can persist and exert their function effectively in a disease state, where a broad spectrum of inflammatory mediators could inactivate Tregs. In this study, we investigated the potential of mesenchymal stem cell (MSC)-derived exosomes to promote and sustain Tregs function. MSC-conditioned media (MSC-CM) cultured Tregs were more suppressive in both polyclonal and allogeneic responses and were resistant to inflammatory stimulation in vitro compared with the controls. A similar enhancement of Treg function was also observed by culturing Tregs with MSC-derived exosomes alone. The enhanced suppressive activity and stability of Treg cultured in MSC-CM was reduced when exosomes were depleted from MSC-CM. We identified that MSC-derived exosomes could upregulate the expression of LC3(II/I), phosphorylate Jak3 and Stat5 to promote Treg survival, and regulate FOXP3 expression in Tregs. Overall, our study demonstrates that MSC-derived exosomes are capable of enhancing Hucb-Tregs function and stability by activating autophagy and Stat5 signalling pathways. Our findings provide a strong rationale for utilizing MSC-derived exosomes as an effective strategy to enhance Treg function, and improve the overall Tregs-based cell therapy landscape.

Recirculating Foxp3+ regulatory T cells are restimulated in the thymus under Aire control

Thymically-derived Foxp3+ regulatory T cells (Treg) critically control immunological tolerance. These cells are generated in the medulla through high affinity interactions with medullary thymic epithelial cells (mTEC) expressing the Autoimmune regulator (Aire). Recent advances have revealed that thymic Treg contain not only developing but also recirculating cells from the periphery. Although Aire is implicated in the generation of Foxp3+ Treg, its role in the biology of recirculating Treg remains elusive. Here, we show that Aire regulates the suppressive signature of recirculating Treg independently of the remodeling of the medullary 3D organization throughout life where Treg reside. Accordingly, the adoptive transfer of peripheral Foxp3+ Treg in AireKO recipients led to an impaired suppressive signature upon their entry into the thymus. Furthermore, recirculating Treg from AireKO mice failed to attenuate the severity of multiorgan autoimmunity, demonstrating that their suppressive function is altered. Using bone marrow chimeras, we reveal that mTEC-specific expression of Aire controls the suppressive signature of recirculating Treg. Finally, mature mTEC lacking Aire were inefficient in stimulating peripheral Treg both in polyclonal and antigen-specific co-culture assays. Overall, this study demonstrates that Aire confers to mTEC the ability to restimulate recirculating Treg, unravelling a novel function for this master regulator in Treg biology.

Analysis of selected polymorphisms in FOXP3 gene in a cohort of Egyptian patients with schizophrenia

BACKGROUND

Schizophrenia is a chronic mental disorder with different symptoms. The environmental and genetic factors are suggested to be the etiology of schizophrenia. However, the exact cause and pathogenesis of schizophrenia are still unclear. Different studies suggested that the immune system may have a role in schizophrenia. A genetic study found a relation between the disease and the HLA region on the sixth chromosome. Regulatory T cells (Treg) have a role in the regulation of immune response, especially the balance between TH1 and TH2 cells. The FOXP3 protein is a key regulator for Treg cell's functions. FOXP3 is a transcriptional factor, and its gene is present on the short arm of the X chromosome. The selected SNPs present in the promoter region which act as binding sites for transcriptional factors. This study investigated FOXP3 gene polymorphisms (rs3761548, rs3761549, and rs2232365) in Egyptian patients with schizophrenia. There are no previous studies about the association of FOXP3 gene polymorphisms with schizophrenia. The three selected single-nucleotide polymorphisms (SNPs) were investigated using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for 125 schizophrenia patients and 160 healthy controls. The Positive and Negative Syndrome Scale (PANSS) was used to evaluate patients with schizophrenia.

RESULTS

No significant associations were found between schizophrenia patients and healthy controls for the alleles and genotypes of the selected SNPs (P-value > 0.05). However, a significant association with ACC and ATC haplotypes was detected (P-value 0.001). No significant association was detected between the PANSS score and any of the studied SNPs.

CONCLUSION

The ATC haplotype of rs2232365, rs3761549, and rs3761548 could be considered a risk factor for schizophrenia in Egyptian patients.

The E-Id Axis Instructs Adaptive Versus Innate Lineage Cell Fate Choice and Instructs Regulatory T Cell Differentiation

Immune responses are primarily mediated by adaptive and innate immune cells. Adaptive immune cells, such as T and B cells, evoke antigen-specific responses through the recognition of specific antigens. This antigen-specific recognition relies on the V(D)J recombination of immunoglobulin (Ig) and T cell receptor (TCR) genes mediated by recombination-activating gene (Rag)1 and Rag2 (Rag1/2). In addition, T and B cells employ cell type-specific developmental pathways during their activation processes, and the regulation of these processes is strictly regulated by the transcription factor network. Among these factors, members of the basic helix-loop-helix (bHLH) transcription factor mammalian E protein family, including E12, E47, E2-2, and HEB, orchestrate multiple adaptive immune cell development, while their antagonists, Id proteins (Id1-4), function as negative regulators. It is well established that a majority of T and B cell developmental trajectories are regulated by the transcriptional balance between E and Id proteins (the E-Id axis). E2A is critically required not only for B cell but also for T cell lineage commitment, whereas Id2 and Id3 enforce the maintenance of naïve T cells and naïve regulatory T (Treg) cells. Here, we review the current knowledge of E- and Id-protein function in T cell lineage commitment and Treg cell differentiation.

Distinct molecular and immune hallmarks of inflammatory arthritis induced by immune checkpoint inhibitors for cancer therapy

Immune checkpoint inhibitors are associated with immune-related adverse events (irAEs), including arthritis (arthritis-irAE). Management of arthritis-irAE is challenging because immunomodulatory therapy for arthritis should not impede antitumor immunity. Understanding of the mechanisms of arthritis-irAE is critical to overcome this challenge, but the pathophysiology remains unknown. Here, we comprehensively analyze peripheral blood and/or synovial fluid samples from 20 patients with arthritis-irAE, and unmask a prominent Th1-CD8+ T cell axis in both blood and inflamed joints. CX3CR1hi CD8+ T cells in blood and CXCR3hi CD8+ T cells in synovial fluid, the most clonally expanded T cells, significantly share TCR repertoires. The migration of blood CX3CR1hi CD8+ T cells into joints is possibly mediated by CXCL9/10/11/16 expressed by myeloid cells. Furthermore, arthritis after combined CTLA-4 and PD-1 inhibitor therapy preferentially has enhanced Th17 and transient Th1/Th17 cell signatures. Our data provide insights into the mechanisms, predictive biomarkers, and therapeutic targets for arthritis-irAE.

Effects of Fisetin on Allergic Contact Dermatitis via Regulating the Balance of Th17/Treg in Mice

Background. Allergic contact dermatitis (ACD) is a form of chronic cutaneous inflammatory disease of immunological origin that has adverse impacts on patient quality of life, underscoring the need for the development of safe and effective therapeutic agents to treat affected individuals. Fisetin is a Chinese herbal preparation that reportedly exhibits antitumor, antioxidant, antimicrobial, anticoagulatory, and antimalarial activity. In the current report, the immunomodulatory activity of fisetin was appraised by assessing its impact on balance between regulatory T (Treg) and Th17 cells in an ACD model. Methods. BALB/c mice ( $n=60$ ) were randomized into control, ACD model, CTX positive control (20 mg/kg), and fisetin treatment groups (three dose levels: 2, 4, or 8 mg/kg). ACD induction was achieved by sensitizing mice on the shaved ventral abdomen via the application of 5% DNFB (50 μL) on days 1 and 2, followed by rechallenge in the right ear with 5% DNFB (20 μL) on day 5. Beginning on day 1, immunized mice were intraperitoneally injected with the appropriate fisetin dose (in saline) once per day for 7 days. On day 7, ear swelling, transcription factor expression, Th17/Treg cell populations, and cytokine production were assessed in vivo. Results. Fisetin treatment significantly suppressed ear swelling and associated inflammatory cell infiltration, besides reducing the production of Th17 cytokines (IL-17, TNF-α, and IL-6) and the expression of the Th17 lineage transcription factor RORγt while simultaneously enhancing Treg-specific cytokine production (TGF-β and IL-10) and the expression of the Treg lineage transcription factor Foxp3, thereby restoring the Th17/Treg cell in ACD mice. Conclusions. These data indicate that fisetin exhibits immunomodulatory activity and can alter the Th17/Treg cell balance, highlighting its potential value as a treatment drug for ACD.

Human umbilical cord-derived mesenchymal stem cells alleviate insulin resistance in diet-induced obese mice via an interaction with splenocytes

Background

Previous research has demonstrated that the spleen plays an important role in mesenchymal stem cell (MSC)-mediated alleviation of acute inflammation, as MSC infusion increases the spleen-derived anti-inflammatory cytokine interleukin 10 (IL-10) levels. However, studies on splenic involvement in MSC-induced protection against chronic inflammatory diseases are limited. Obesity is characterized by chronic low-grade inflammation, a key driver of insulin resistance. This study aims to evaluate the effects of MSCs on obesity-related insulin resistance and explore the underlying mechanism, particularly regarding splenic involvement.

Methods

We induced obesity in mice by feeding them high-fat diets for 20 weeks. Human umbilical cord-derived MSCs (UC-MSCs) were systemically infused into the obese mice once per week for 6 weeks. Systemic glucose metabolic homeostasis and insulin sensitivity in epididymal adipose tissue (EAT) were evaluated. Then, we conducted in vivo blockade of IL-10 during UC-MSC infusion by intraperitoneally administrating an IL-10-neutralizing antibody twice per week. We also investigated the therapeutic effects of UC-MSCs on obese mice after removal of the spleen by splenectomy.

Results

UC-MSC infusions improved systemic metabolic homeostasis and alleviated insulin resistance in EAT but elicited no change in weight. Despite rare engraftment of UC-MSCs in EAT, UC-MSC infusions attenuated insulin resistance in EAT by polarizing macrophages into the M2 phenotype, coupled with elevated serum IL-10 levels. In vivo blockade of IL-10 blunted the effects of UC-MSCs on obese mice. Furthermore, UC-MSCs overwhelmingly homed to the spleen, and the ability of UC-MSCs to elevate serum IL-10 levels and alleviate insulin resistance was impaired in the absence of the spleen. Further in vivo and in vitro studies revealed that UC-MSCs promoted the capacity of regulatory T cells (Treg cells) to produce IL-10 in the spleen.

Conclusions

Our results demonstrated that UC-MSCs elevated serum IL-10 levels and subsequently promoted macrophage polarization, leading to alleviation of insulin resistance in EAT. The underlying mechanism was that UC-MSCs improved the capacity of Treg cells to produce IL-10 in the spleen. Our findings indicated that the spleen played a critical role in amplifying MSC-mediated immunomodulatory effects, which may contribute to maximizing MSC efficacy in clinical applications in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02791-6.

microRNA-142 guards against autoimmunity by controlling Treg cell homeostasis and function

Regulatory T (Treg) cells are critical in preventing aberrant immune responses. Posttranscriptional control of gene expression by microRNA (miRNA) has recently emerged as an essential genetic element for Treg cell function. Here, we report that mice with Treg cell-specific ablation of miR-142 (hereafter Foxp3CremiR-142fl/fl mice) developed a fatal systemic autoimmune disorder due to a breakdown in peripheral T-cell tolerance. Foxp3CremiR-142fl/fl mice displayed a significant decrease in the abundance and suppressive capacity of Treg cells. Expression profiling of miR-142-deficient Treg cells revealed an up-regulation of multiple genes in the interferon gamma (IFNγ) signaling network. We identified several of these IFNγ-associated genes as direct miR-142-3p targets and observed excessive IFNγ production and signaling in miR-142-deficient Treg cells. Ifng ablation rescued the Treg cell homeostatic defect and alleviated development of autoimmunity in Foxp3CremiR-142fl/fl mice. Thus, our findings implicate miR-142 as an indispensable regulator of Treg cell homeostasis that exerts its function by attenuating IFNγ responses.