TGF-beta requires CTLA-4 early after T cell activation to induce FoxP3 and generate adaptive CD4+CD25+ regulatory cells

The clinical association of programmed death-1/PD-L1 axis, myeloid derived suppressor cells subsets and regulatory T cells in peripheral blood of stable COPD patients

Background

Myeloid-derived suppressor cells (MDSCs) have crucial immunosuppressive role in T cell dysfunction in various disease processes. However, the role of MDSCs and their impact on Tregs in COPD have not been fully understood. The aim of the present study is to investigate the immunomodulatory role of MDSCs and their potential impact on the expansion and function of Tregs in COPD patients.

Methods

Peripheral blood samples were collected to analyze circulating MDSCs, Tregs, PD-1/PD-L1 expression to assess the immunomodulatory role of MDSC and their potential impact on the expansion and function of Treg in COPD. A total of 54 COPD patients and 24 healthy individuals were enrolled in our study. Flow cytometric analyses were performed to identify granulocytic MDSCs (G-MDSCs), monocytic MDSCs (M-MDSCs), Tregs, and the expression of PD-1/PD-L1(L2) on MDSCs and Tregs in peripheral blood.

Results

Our results revealed a significantly higher percentage of G-MDSCs and M-MDSCs (p < 0.001) in COPD patients compared to the healthy controls. Additionally, a significantly higher proportion of peripheral blood Tregs was observed in COPD patients. Furthermore, an increased expression of cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) on Tregs (p < 0.01) was detected in COPD patients. The expression of PD-1 on CD4+ Tcells and Tregs, but not CD8+Tcells, was found to be increased in patients with COPD compared to controls. Furthermore, an elevated expression of PD-L1 on M-MDSCs (p < 0.01) was also observed in COPD patients. A positive correlation was observed between the accumulation of M-MDSCs and Tregs in COPD patients. Additionally, the percentage of circulating M-MDSCs is positively associated with the level of PD-1 (r = 0.51, p < 0.0001) and CTLA-4 (r = 0.42, p = 0.0014) on Tregs in COPD.

Conclusion

The recruitment of MDSCs, accumulation of Tregs, and up-regulation of CTLA-4 on Treg in COPD, accompanied by an increased level of PD-1/PD-L1, suggest PD-1/PD-L1 axis may be potentially involved in MDSCs-induced the expansion and activation of Treg at least partially in COPD.

Pulmonary toxicity of immune checkpoint immunotherapy

Cancer remains a leading cause of mortality on a global scale. Lung cancer, specifically non-small cell lung cancer (NSCLC), is a prominent contributor to this burden. The management of NSCLC has advanced substantially in recent years, with immunotherapeutic agents, such as immune checkpoint inhibitors (ICIs), leading to improved patient outcomes. Although generally well tolerated, the administration of ICIs can result in unique side effects known as immune-related adverse events (irAEs). The occurrence of irAEs involving the lungs, specifically checkpoint inhibitor pneumonitis (CIP), can have a profound effect on both future therapy options and overall survival. Despite CIP being one of the more common serious irAEs, limited treatment options are currently available, in part due to a lack of understanding of the underlying mechanisms involved in its development. In this Review, we aim to provide an overview of the epidemiology and clinical characteristics of CIP, followed by an examination of the emerging literature on the pathobiology of this condition.

Single-cell and genetic multi-omics analysis combined with experiments confirmed the signature and potential targets of cuproptosis in hepatocellular carcinoma

Background: Cuproptosis, as a recently discovered type of programmed cell death, occupies a very important role in hepatocellular carcinoma (HCC) and provides new methods for immunotherapy; however, the functions of cuproptosis in HCC are still unclear. Methods: We first analyzed the transcriptome data and clinical information of 526 HCC patients using multiple algorithms in R language and extensively described the copy number variation, prognostic and immune infiltration characteristics of cuproptosis related genes (CRGs). Then, the hub CRG related genes associated with prognosis through LASSO and Cox regression analyses and constructed a prognostic prediction model including multiple molecular markers and clinicopathological parameters through training cohorts, then this model was verified by test cohorts. On the basis of the model, the clinicopathological indicators, immune infiltration and tumor microenvironment characteristics of HCC patients were further explored via bioinformation analysis. Then, We further explored the key gene biological function by single-cell analysis, cell viability and transwell experiments. Meantime, we also explored the molecular docking of the hub genes. Results: We have screened 5 hub genes associated with HCC prognosis and constructed a prognosis prediction scoring model. And the model results showed that patients in the high-risk group had poor prognosis and the expression levels of multiple immune markers, including PD-L1, CD276 and CTLA4, were higher than those patients in the low-risk group. We found a significant correlation between risk score and M0 macrophages and memory CD4+ T cells. And the single-cell analysis and molecular experiments showed that BEX1 were higher expressed in HCC tissues and deletion inhibited the proliferation, invasion and migration and EMT pathway of HCC cells. Finally, it was observed that BEX1 could bind to sorafenib to form a stable conformation. Conclusion: The study not only revealed the multiomics characteristics of CRGs in HCC but also constructed a new high-accuracy prognostic prediction model. Meanwhile, BEX1 were also identified as hub genes that can mediate the cuproptosis of hepatocytes as potential therapeutic targets for HCC.

Current understanding of CTLA-4: from mechanism to autoimmune diseases

Autoimmune diseases (ADs) are characterized by the production of autoreactive lymphocytes, immune responses to self-antigens, and inflammation in related tissues and organs. Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is majorly expressed in activated T cells and works as a critical regulator in the inflammatory response. In this review, we first describe the structure, expression, and how the signaling pathways of CTLA-4 participate in reducing effector T-cell activity and enhancing the immunomodulatory ability of regulatory T (Treg) cells to reduce immune response, maintain immune homeostasis, and maintain autoimmune silence. We then focused on the correlation between CTLA-4 and different ADs and how this molecule regulates the immune activity of the diseases and inhibits the onset, progression, and pathology of various ADs. Finally, we summarized the current progress of CTLA-4 as a therapeutic target for various ADs.

Zinc Modulates the Priming of T Helper 1, T Helper 17, and T Regulatory Cells in Allogeneic and Autologous in vitro Models

Introduction

Zinc is essential for the growth and differentiation of immune cells. Zinc insufficiency affects immune system function, thereby increasing infection susceptibility, autoimmunity, and allergies. Here, we aimed to determine the effects of zinc supplementation on T cell subpopulations, regulatory T (Tregs), T helper 1 (Th1), and T helper 17 (Th17) cells, in mixed lymphocyte cultures (MLC).

Methods

Allogeneic immune reactions were imitative using mixed lymphocyte cultures, followed by incubation with zinc to further monitor their effects. Cells were analyzed by flow cytometry. Production of Interferon-gamma (IFNγ), Interleukin-17 A (IL17A), and IL10 were analyzed by enzyme-linked immunosorbent assay. Th1 cell-specific Tbet, Th17 cell-specific RORC2, and Tregs-specific Foxp3 expression levels were determined by quantitative real-time PCR.

Results

Zinc supplementation at a physiological dose significantly increased CD4+ Foxp3+ Tregs and CD25+ Foxp3+ Tregs numbers and slightly decreased CD4+ RORC2+ and CD25+ RORC2+ Th17 cell numbers. A significant reduction in IFNγ production was observed in both restimulated T cells with autologous peripheral blood mononuclear cell (PBMC) and allogeneic PBMC compared to that in untreated T cells. Zinc significantly reduced IL17 expression, but the increase in IL10 expression was insignificant. In zinc-supplemented MLC, a non-significant decrease in Th1 or Th17 cell-specific transcription factors expression was observed, whereas there was a significant increase in Tregs-specific transcription factor expression.

Conclusion

Zinc can stabilize Tregs participating in adverse immune reactions or in an in vitro transplantation model.

Current Understanding of Cytotoxic T Lymphocyte Antigen-4 (CTLA-4) Signaling in T-Cell Biology and Disease Therapy

Cytotoxic T lymphocyte antigen-4 (CTLA-4) is an immune checkpoint molecule that is mainly expressed on activated T cells and regulatory T (Treg) cells that inhibits T-cell activation and regulates immune homeostasis. Due to the crucial functions of CTLA-4 in T-cell biology, CTLA-4-targeted immunotherapies have been developed for autoimmune disease as well as cancers. CTLA-4 is known to compete with CD28 to interact with B7, but some studies have revealed that its downstream signaling is independent of its ligand interaction. As a signaling domain of CTLA-4, the tyrosine motif plays a role in inhibiting T-cell activation. Recently, the lysine motif has been shown to be required for the function of Treg cells, emphasizing the importance of CTLA-4 signaling. In this review, we summarize the current understanding of CTLA-4 biology and molecular signaling events and discuss strategies to target CTLA-4 signaling for immune modulation and disease therapy.

Small extracellular vesicles derived from PD-L1-modified mesenchymal stem cell promote Tregs differentiation and prolong allograft survival

We aimed to explore whether programmed cell death protein-1 ligand (PD-L1) modification on small extracellular vesicles (sEVs) could promote T regulatory cells (Tregs) differentiation. In this study, it was confirmed that under physiological conditions, PD-L1 expression was minimal in the MSCs and absent in the MSC-sEVs. A vector harboring the PD-L1 gene was constructed and transfected into bone marrow mesenchymal stem cells (BM-MSCs). By extracting the sEVs of these modified BM-MSCs and monitoring the expression of the PD-L1 protein, however, PD-L1 expression was substantially increased in the MSCs and concentrated in the sEVs. Then, the rat naïve CD4 + T cells were cocultured with the sEVs derived from the PD-L1-modified MSCs (sEVs^PD-L1). By flow cytometry, a higher percentage of Tregs and anti-inflammatory downstream cytokines (including IL-2, IFN-γ, TGF-β, IL-10) was detected in the sEVs^PD-L1 group than that in the control group treated by either sEVs in wild type, modified by empty vector, or blank control. Suppressive effect on CD4 + T cell proliferation serves as additional evidence to support the immunoregulation capacity of sEVs^PD-L1. The animal model of vascularized composite allograft further confirmed that PD-L1-modified sEVs induce an immune tolerance, by clinically observation, histopathology, T cell fate and cell product. In conclusion, sEVs^PD-L1 efficiently promotes Treg cell differentiation in vitro and in vivo, which suggests their therapeutic potential in the treatment of allograft rejection.

Neuropilin-1 Identifies a New Subpopulation of TGF-β-Induced Foxp3+ Regulatory T Cells With Potent Suppressive Function and Enhanced Stability During Inflammation

CD4⁺Foxp3⁺ regulatory T cells (Tregs) play a crucial role in preventing autoimmunity and inflammation. There are naturally-derived in the thymus (tTreg), generated extrathymically in the periphery (pTreg), and induced in vitro culture (iTreg) with different characteristics of suppressiveness, stability, and plasticity. There is an abundance of published data on neuropilin-1 (Nrp-1) as a tTreg marker, but little data exist on iTreg. The fidelity of Nrp-1 as a tTreg marker and its role in iTreg remains to be explored. This study found that Nrp-1 was expressed by a subset of Foxp3⁺CD4⁺T cells in the central and peripheral lymphoid organs in intact mice, as well as in iTreg. Nrp-1⁺iTreg and Nrp-1^-iTreg were adoptively transferred into a T cell-mediated colitis model to determine their ability to suppress inflammation. Differences in gene expression between Nrp-1⁺ and Nrp-1^-iTreg were analyzed by RNA sequencing. We demonstrated that the Nrp-1⁺ subset of the iTreg exhibited enhanced suppressive function and stability compared to the Nrp-1^- counterpart both in vivo and in vitro, partly depending on IL-10. We found that Nrp-1 is not an exclusive marker of tTreg, however, it is a biomarker identifying a new subset of iTreg with enhanced suppressive function, implicating a potential for Nrp-1⁺iTreg cell therapy for autoimmune and inflammatory diseases.

The Bright and the Dark Side of TGF-β Signaling in Hepatocellular Carcinoma: Mechanisms, Dysregulation, and Therapeutic Implications

Simple Summary

Transforming growth factor β (TGF-β) signaling is a preeminent regulator of diverse cellular and physiological processes. Frequent dysregulation of TGF-β signaling has been implicated in cancer. In hepatocellular carcinoma (HCC), the most prevalent form of primary liver cancer, the autocrine and paracrine effects of TGF-β have paradoxical implications. While acting as a potent tumor suppressor pathway in the early stages of malignancy, TGF-β diverts to a promoter of tumor progression in the late stages, reflecting its bright and dark natures, respectively. Within this context, targeting TGF-β represents a promising therapeutic option for HCC treatment. We discuss here the molecular properties of TGF-β signaling in HCC, attempting to provide an overview of its effects on tumor cells and the stroma. We also seek to evaluate the dysregulation mechanisms that mediate the functional switch of TGF-β from a tumor suppressor to a pro-tumorigenic signal. Finally, we reconcile its biphasic nature with the therapeutic implications.

Abstract

Hepatocellular carcinoma (HCC) is associated with genetic and nongenetic aberrations that impact multiple genes and pathways, including the frequently dysregulated transforming growth factor β (TGF-β) signaling pathway. The regulatory cytokine TGF-β and its signaling effectors govern a broad spectrum of spatiotemporally regulated molecular and cellular responses, yet paradoxically have dual and opposing roles in HCC progression. In the early stages of tumorigenesis, TGF-β signaling enforces profound tumor-suppressive effects, primarily by inducing cell cycle arrest, cellular senescence, autophagy, and apoptosis. However, as the tumor advances in malignant progression, TGF-β functionally switches to a pro-tumorigenic signal, eliciting aggressive tumor traits, such as epithelial–mesenchymal transition, tumor microenvironment remodeling, and immune evasion of cancer cells. On this account, the inhibition of TGF-β signaling is recognized as a promising therapeutic strategy for advanced HCC. In this review, we evaluate the functions and mechanisms of TGF-β signaling and relate its complex and pleiotropic biology to HCC pathophysiology, attempting to provide a detailed perspective on the molecular determinants underlying its functional diversion. We also address the therapeutic implications of the dichotomous nature of TGF-β signaling and highlight the rationale for targeting this pathway for HCC treatment, alone or in combination with other agents.

The foundations of immune checkpoint blockade and the ipilimumab approval decennial

Cancer immunity, and the potential for cancer immunotherapy, have been topics of scientific discussion and experimentation for over a hundred years. Several successful cancer immunotherapies - such as IL-2 and interferon-α (IFNα) - have appeared over the past 30 years. However, it is only in the past decade that immunotherapy has made a broad impact on patient survival in multiple high-incidence cancer indications. The emergence of immunotherapy as a new pillar of cancer treatment (adding to surgery, radiation, chemotherapy and targeted therapies) is due to the success of immune checkpoint blockade (ICB) drugs, the first of which - ipilimumab - was approved in 2011. ICB drugs block receptors and ligands involved in pathways that attenuate T cell activation - such as cytotoxic T lymphocyte antigen 4 (CTLA4), programmed cell death 1 (PD1) and its ligand, PDL1 - and prevent, or reverse, acquired peripheral tolerance to tumour antigens. In this Review we mark the tenth anniversary of the approval of ipilimumab and discuss the foundational scientific history of ICB, together with the history of the discovery, development and elucidation of the mechanism of action of the first generation of drugs targeting the CTLA4 and PD1 pathways.

Isoform specific anti-TGFβ therapy enhances antitumor efficacy in mouse models of cancer

TGFβ is a potential target in cancer treatment due to its dual role in tumorigenesis and homeostasis. However, the expression of TGFβ and its inhibition within the tumor microenvironment has mainly been investigated in stroma-heavy tumors. Using B16 mouse melanoma and CT26 colon carcinoma as models of stroma-poor tumors, we demonstrate that myeloid/dendritic cells are the main sources of TGFβ1 and TGFβ3. Depending on local expression of TGFβ isoforms, isoform specific inhibition of either TGFβ1 or TGFβ3 may be effective. The TGFβ signature of CT26 colon carcinoma is defined by TGFβ1 and TGFβ1 inhibition results in tumor delay; B16 melanoma has equal expression of both isoforms and inhibition of either TGFβ1 or TGFβ3 controls tumor growth. Using T cell functional assays, we show that the mechanism of tumor delay is through and dependent on enhanced CD8+ T cell function. To overcome the local immunosuppressive environment, we found that combining TGFβ inhibition with immune checkpoint blockade results in improved tumor control. Our data suggest that TGFβ inhibition in stroma poor tumors shifts the local immune environment to favor tumor suppression.

The Kynurenine Pathway-New Linkage between Innate and Adaptive Immunity in Autoimmune Endocrinopathies

The kynurenine pathway (KP) is highly regulated in the immune system, where it promotes immunosuppression in response to infection or inflammation. Indoleamine 2,3-dioxygenase 1 (IDO1), the main enzyme of KP, has a broad spectrum of activity on immune cells regulation, controlling the balance between stimulation and suppression of the immune system at sites of local inflammation, relevant to a wide range of autoimmune and inflammatory diseases. Various autoimmune diseases, among them endocrinopathies, have been identified to date, but despite significant progress in their diagnosis and treatment, they are still associated with significant complications, morbidity, and mortality. The precise cellular and molecular mechanisms leading to the onset and development of autoimmune disease remain poorly clarified so far. In breaking of tolerance, the cells of the innate immunity provide a decisive microenvironment that regulates immune cells’ differentiation, leading to activation of adaptive immunity. The current review provided a comprehensive presentation of the known role of IDO1 and KP activation in the regulation of the innate and adaptive arms of the immune system. Significant attention has been paid to the immunoregulatory role of IDO1 in the most prevalent, organ-specific autoimmune endocrinopathies—type 1 diabetes mellitus (T1DM) and autoimmune thyroiditis.

In vitro Immunomodulatory Effects of Human Umbilical Cord-Derived Mesenchymal Stem Cells on Peripheral Blood Cells from Warm Autoimmune Hemolytic Anemia Patients

INTRODUCTION

Autoimmune hemolytic anemia is a potentially lethal disease characterized by autoimmune hemolysis. Although human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) have been reported as a promising therapy, there is limited evidence regarding warm autoimmune hemolytic anemia (wAIHA) patients. This study aimed to investigate the potential therapeutic effects of hUC-MSCs via immune regulation in wAIHA patients.

METHODS

Peripheral blood mononuclear cells (PBMCs) from 10 wAIHA patients and 8 healthy controls were isolated from peripheral blood and cultured for 3 days with or without the presence of hUC-MSCs; PBMCs were co-cultured with hUC-MSCs using Transwell assays. The supernatant cytokine levels were measured after culture through AimPlex Multiple Immunoassays for Flow, including IL-2, IL-4, IL-10, IFN-γ, TNF-α, and IL-17A. The percentages of regulatory T cells, regulatory B cells, and Th1/Th2 in PBMCs were also assessed before and after culturing.

RESULTS

In the wAIHA group, hUC-MSCs could upregulate the Treg and Breg proportions after culturing for 3 days, and the Treg and Breg percentages increased after co-culturing with hUC-MSCs in the wAIHA group compared with PBMC cultured alone for 3 days (8.29 ± 8.59 vs. 6.82 ± 1.32, 3.82 ± 1.87 vs. 1.75 ± 1.20, respectively). Compared with the PBMC wAIHA group, the levels of TNF-α (2.13 ± 2.07 vs. 16.20 ± 21.13 pg/mL, p = 0.019) and IL-10 (10.51 ± 18.42 vs. 37.78 ± 44.20 pg/mL, p = 0.012) were significantly elevated in the PBMC + hUC-MSCs wAIHA group.

CONCLUSION

The hUC-MSCs contributed to the increasing proportion of regulatory cell populations in PBMCs of wAIHA patients, thereby potentially regulating autoimmune response; thus, hUC-MSCs may be a promising approach for wAIHA treatment.

Recruitment and Expansion of Tregs Cells in the Tumor Environment-How to Target Them?

Simple Summary

The immune response against cancer is generated by effector T cells, among them cytotoxic CD8⁺ T cells that destroy cancer cells and helper CD4⁺ T cells that mediate and support the immune response. This antitumor function of T cells is tightly regulated by a particular subset of CD4⁺ T cells, named regulatory T cells (Tregs), through different mechanisms. Even if the complete inhibition of Tregs would be extremely harmful due to their tolerogenic role in impeding autoimmune diseases in the periphery, the targeted blockade of their accumulation at tumor sites or their targeted depletion represent a major therapeutic challenge. This review focuses on the mechanisms favoring Treg recruitment, expansion and stabilization in the tumor microenvironment and the therapeutic strategies developed to block these mechanisms.

Abstract

Regulatory T cells (Tregs) are present in a large majority of solid tumors and are mainly associated with a poor prognosis, as their major function is to inhibit the antitumor immune response contributing to immunosuppression. In this review, we will investigate the mechanisms involved in the recruitment, amplification and stability of Tregs in the tumor microenvironment (TME). We will also review the strategies currently developed to inhibit Tregs’ deleterious impact in the TME by either inhibiting their recruitment, blocking their expansion, favoring their plastic transformation into other CD4⁺ T-cell subsets, blocking their suppressive function or depleting them specifically in the TME to avoid severe deleterious effects associated with Treg neutralization/depletion in the periphery and normal tissues.

Post-Translational Regulations of Foxp3 in Treg Cells and Their Therapeutic Applications

Regulatory T (Treg) cells are indispensable for immune homeostasis due to their roles in peripheral tolerance. As the master transcription factor of Treg cells, Forkhead box P3 (Foxp3) strongly regulates Treg function and plasticity. Because of this, considerable research efforts have been directed at elucidating the mechanisms controlling Foxp3 and its co-regulators. Such work is not only advancing our understanding on Treg cell biology, but also uncovering novel targets for clinical manipulation in autoimmune diseases, organ transplantation, and tumor therapies. Recently, many studies have explored the post-translational regulation of Foxp3, which have shown that acetylation, phosphorylation, glycosylation, methylation, and ubiquitination are important for determining Foxp3 function and plasticity. Additionally, some of these targets have been implicated to have great therapeutic values. In this review, we will discuss emerging evidence of post-translational regulations on Foxp3 in Treg cells and their exciting therapeutic applications.

Adipose Tissue T Regulatory Cells: Implications for Health and Disease

Obesity dramatically increases the risk of numerous conditions, including type 2 diabetes mellitus and other components of the metabolic syndrome. Pro-inflammatory changes that occur in adipose tissue are critical to the pathogenesis of these obesity-induced complications. Adipose tissue is one of the body's largest endocrine organs, and the cells that comprise the adipose tissue immunoenvironment secrete multiple factors (including adipokines and cytokines) that impact systemic metabolism. In particular, immunosuppressive regulatory T cells (Tregs) decline in obesity, partly in response to its complex interaction with adipocytes, and this decline contributes to disruption of the typical homeostasis observed in lean adipose tissue. Although the regulation of Treg differentiation, function, and enrichment is incompletely understood, factors including various cell-surface co-stimulatory molecules, certain lipid species, and cytokines such as PPARγ, adiponectin, and leptin are important mediators. It is also clear that there may be depot-specific differences in Tregs, rendering adipose tissue Tregs distinct from lymphoid or circulating Tregs, with implications on maintenance and functionality. While most of these findings are derived from studies in murine models, comparatively little is known about the human adipose tissue Treg signature, which requires further investigation.

Ubiquitin-Dependent Regulation of Treg Function and Plasticity

As an indispensable part of peripheral tolerance, regulatory T (Treg) cells play an important role in immune homeostasis by suppressing other immune cells. Behind this function is a complex network of transcription factors and signaling cascades that regulates the function and plasticity of regulatory T cells. Among these, Forkhead box P3 (Foxp3) is considered as the master transcription factor, and its stability will influence the function and viability of Treg cells. Because of this, understanding the mechanisms that regulate Foxp3 and its co-regulators will provide more understanding to Treg cells and uncover more targets to manipulate Treg cells in treating autoimmune diseases, organ transplantation, and tumor. Interestingly, several recent studies show that ubiquitin-dependent pathways are important regulators of Foxp3, which suggest both great scientific and therapeutic values. In this chapter, we cover emerging evidence of ubiquitin-dependent, posttranslational regulation of Treg function and plasticity.

Tregs in Autoimmune Uveitis

Uveitis is a chronic disease with relapsing and remitting ocular attack, which requires corticosteroids and systemic immunosuppression to prevent severe vision loss. Classically, uveitis is referred to an autoimmune disease, mediated by pro-inflammatory Th17 cells and immunosuppressive CD4+CD25+FoxP3+ T-regulatory cells (Tregs). More and more evidence indicates that Tregs are involved in development, resolution, and remission of uveitis. Clinically, many researchers have conducted quantitative and functional analyses of peripheral blood from patients with different subtypes of uveitis, in an attempt to find the changing rules of Tregs. Consistently, using the experimental autoimmune uveitis (EAU) model, researchers have explored the development and resolution mechanism of uveitis in many aspects. In addition, many drug and Tregs therapy investigations have yielded encouraging results. In this chapter, we introduced the current understanding of Tregs, summarized the clinical changes in the number and function of patients with uveitis and the immune mechanism of Tregs involved in EAU model, as well as discussed the progress and shortcomings of Tregs-related drug therapy and Tregs therapy. Although the exact mechanism of Tregs-mediated uveitis protection remains to be elucidated, the strategy of Tregs regulation may provide a specific and meaningful way for the prevention and treatment of uveitis.

TNF-TNFR2 Signal Plays a Decisive Role in the Activation of CD4+Foxp3+ Regulatory T Cells: Implications in the Treatment of Autoimmune Diseases and Cancer

The puzzling biphasic or dual roles of tumor necrosis factor α (TNF) in the inflammatory and immune responses are likely to be mediated by distinct signaling pathways transduced by one of its two receptors, e.g., TNF receptor type I (TNFR1) and TNF receptor type II (TNFR2). Unlike TNFR1 that is ubiquitously expressed on almost all types of cells, the expression of TNFR2 is rather restricted to certain types of cells, such as T lymphocytes. There is now compelling evidence that TNFR2 is preferentially expressed by CD4⁺Foxp3⁺ regulatory T cells (Tregs), and TNFR2 plays a decisive role in the activation, expansion, in vivo function, and phenotypical stability of Tregs. In this chapter, the current understanding of the molecular basis and signaling pathway of TNF-TNFRs signal is introduced. Latest studies that have further supported and substantiated the pivotal role of TNF-TNFR2 interaction in Tregs biology and its molecular basis are discussed. The research progress regarding TNFR2-targeting treatment for autoimmune diseases and cancer is analyzed. Future study should focus on the further understanding of molecular mechanism underlying Treg-stimulatory effect of TNFR2 signal, as well as on the translation of research findings into therapeutic benefits of human patients with autoimmune diseases, allergy, allograft rejection, and cancer.

Regulation of Treg Functions by the Ubiquitin Pathway

Regulatory T (Tregs) cells, required to maintain immune homeostasis, have significant power in disease outcomes. Treg dysfunction, predominantly characterized by the loss of the master transcription factor FoxP3 and the acquisition of T_eff-like phenotypes, can promote autoimmunity as well as enhance anti-tumor immunity. As FoxP3 expression and stability are pinnacle for Treg suppressive functions, understanding the pathways that regulate FoxP3 is crucial to ascertain Treg-mediated therapies for autoimmune diseases and cancer. Mechanisms controlling FoxP3 expression and stability range from transcriptional to posttranslational, revealing multiple therapeutic opportunities. While many of the transcriptional pathways have been explored in detail, a recent surge in interest on the posttranslational mechanisms regulating FoxP3 has arisen. Particularly, the role of ubiquitination on Tregs both directly and indirectly involving FoxP3 has gained interest. Here, we summarize the current knowledge on ubiquitin-dependent, FoxP3-mediated control of Treg function as it pertains to human diseases.

Understanding and Targeting Human Cancer Regulatory T Cells to Improve Therapy

Regulatory T cells (Tregs) are critical in maintaining immune homeostasis under various pathophysiological conditions. A growing body of evidence demonstrates that Tregs play an important role in cancer progression and that they do so by suppressing cancer-directed immune responses. Tregs have been targeted for destruction by exploiting antibodies against and small-molecule inhibitors of several molecules that are highly expressed in Tregs-including immune checkpoint molecules, chemokine receptors, and metabolites. To date, these strategies have had only limited antitumor efficacy, yet they have also created significant risk of autoimmunity because most of them do not differentiate Tregs in tumors from those in normal tissues. Currently, immune checkpoint inhibitor (ICI)-based cancer immunotherapies have revolutionized cancer treatment, but the resistance to ICI is common and the elevation of Tregs is one of the most important mechanisms. Therapeutic strategies that can selectively eliminate Tregs in the tumor (i.e. therapies that do not run the risk of causing autoimmunity by affecting normal tissue), are urgently needed for the development of cancer immunotherapies. This chapter discusses specific properties of human Tregs under the context of cancer and the various ways to target Treg for cancer immunotherapy.

Treg Cells and Epigenetic Regulation

The discovery of the epigenetic regulation of Treg cells, a cell population with fundamental immunoregulatory properties, has shed considerable insights into an understanding of the role of these cells in health and disease. Research over the past several years has shown that the interaction of Treg cells with the gut microbiota are critical not only for the development of Treg function in health but also for abnormalities of Treg function that play a critical role in the pathogenesis of human diseases such as the allergic diseases, the autoimmune disorders, and cancer. The equilibrium between phenotypic plasticity and stability of Treg cells is defined by the fine-tuned transcriptional and epigenetic events required to ensure stable expression of Foxp3 in Treg cells. In this chapter, we discuss the molecular events that control Foxp3 gene expression and address the importance of DNA methylation as an important molecular switch that regulates the genetic expression of Treg induction and the possible implications of these findings for the treatment of human diseases characterized by abnormalities of Treg cell function.

CXCR4 inhibition modulates the tumor microenvironment and retards the growth of B16-OVA melanoma and Renca tumors

To determine whether blockade of the chemokine receptor CXCR4 might alter the tumor microenvironment and inhibit tumor growth, we tested the efficacy of the CXCR4 antagonist X4-136 as a single agent and in combination with various immune checkpoint inhibitors in the syngeneic murine melanoma model B16-OVA. We also tested its activity alone and in combination with axitinib in the renal cancer model Renca. We found that X4-136 exhibited potent single agent antitumor activity in the B16-OVA model that was additive to that of an anti-PDL1 antibody. The antitumor activities were associated with a reduction in the number of immunosuppressive regulatory T cells and myeloid-derived suppressor cells and an increase in the number of tumor-specific CD8/perforin cells in the tumor-microenvironment. Apart from these immune effects, X4-136 alone and in combination with checkpoint inhibitors inhibited the Akt/FOXO-3a cell survival pathway in vitro and in vivo, suggesting that it might have antitumor activity independent of its effects on immune cell trafficking. Similar effects on tumor growth and cytotoxic T lymphocytes infiltration were observed in the Renca model. These studies show that the effects of CXCR4 blockade on immune cell trafficking might serve as a useful adjunct to immune checkpoint inhibitors and other therapies in the treatment of cancer.

Immune Checkpoint Inhibitors for the Treatment of Cancer: Clinical Impact and Mechanisms of Response and Resistance

Immune checkpoint inhibitors (ICIs) have made an indelible mark in the field of cancer immunotherapy. Starting with the approval of anti-cytotoxic T lymphocyte-associated protein 4 (anti-CTLA-4) for advanced-stage melanoma in 2011, ICIs-which now also include antibodies against programmed cell death 1 (PD-1) and its ligand (PD-L1)-quickly gained US Food and Drug Administration approval for the treatment of a wide array of cancer types, demonstrating unprecedented extension of patient survival. However, despite the success of ICIs, resistance to these agents restricts the number of patients able to achieve durable responses, and immune-related adverse events complicate treatment. Thus, a better understanding of the requirements for an effective and safe antitumor immune response following ICI therapy is needed. Studies of both tumoral and systemic changes in the immune system following ICI therapy have yielded insight into the basis for both efficacy and resistance. Ultimately, by building on these insights, researchers should be able to combine ICIs with other agents, or design new immunotherapies, to achieve broader and more durable efficacy as well as greater safety. Here, we review the history and clinical utility of ICIs, the mechanisms of resistance to therapy, and local and systemic immune cell changes associated with outcome.

Changes in peripheral immune populations during pregnancy and modulation by probiotics and ω-3 fatty acids

Allergic diseases have become a major health problem, partly due to reduced microbial stimulation and a decreased dietary ω-3/ω-6 long-chain polyunsaturated fatty acid ratio. Prenatal exposures have been reported to influence allergy development, possibly induced via changes in maternal immune regulation. In a randomized double-blind placebo-controlled multicenter allergy prevention trial (PROOM-3), pregnant women were recruited at gestational week 20, and randomized to four study groups, one receiving both L. reuteri oil drops and ω-3 PUFA capsules (n = 22), the second receiving ω-3 PUFA supplementation and placebo regarding L. reuteri (n = 21), the third receiving L. reuteri and placebo regarding ω-3 PUFA (n = 22) and the fourth group receiving placebo capsules and placebo oil drops (n = 23). In this substudy, supplemental and pregnancy-related effects on maternal peripheral immune cell populations during pregnancy were assessed by flow cytometry immune phenotyping at gestational week 20, 32 and 4 days after delivery. The numbers of activated and regulatory T (Treg) cells (CD45RA⁻ Foxp3⁺⁺/CD45RA⁺Foxp3⁺) were reduced after delivery, with the lowest count in the L. reuteri supplemented group compared with the placebo group 4 days after delivery, while the ω-3 PUFA group did not differ from the placebo group. Several treatment-independent changes were observed during and after pregnancy in lymphocytes (CD4⁺/8⁺/19⁺/56⁺/45RA^+/−), CD14⁺16^+/− monocytes, and in subpopulations of T helper cells (Th) CD4⁺CD45RA⁻Tbet⁺ (Th1) and CD4⁺CD45RA⁻RORC⁺ (Th17) cells. In conclusion, probiotic supplementation to the mother during the second half of pregnancy resulted in immunomodulatory effects among activated and resting Treg cells. Furthermore, several systemic immune modifying effects of pregnancy were observed.

The role of B7 family members in the generation of Immunoglobulin

Ig is a Y-shaped protein produced by plasma cells and exerts multiple functions in humoral immunity. There are five groups of Igs including IgA, IgD, IgE, IgG, and IgM, which differ in their heavy chain class. The primary function of Igs includes the neutralization of extrinsic pathogens, agglutination of foreign cells for phagocytosis, precipitation of soluble antigens in serum, and complement fixation. The B cells activated by antigen(s) can differentiate into antibody-producing cells that are called plasma cells and usually matured in the germinal center (GC). Follicular T helper (Tfh) cells crosstalk with antigen-presenting cells and play a crucial role in the development of the GC. Moreover, Tfh cells regulate trafficking through the GC to allow formative interaction with GC B cells that ultimately results in affinity maturation, B-cell memory, and Ig class switching. The B7 family is a series of number of structurally related membrane proteins that bind with a specific receptor to deliver costimulatory or co-inhibitory signals that regulate the activation of T cells in GC. Here, we review and summarize the recent advance of the effects of B7 family members on Ig production and relative diseases.

Destructive Roles of Fibroblast-like Synoviocytes in Chronic Inflammation and Joint Damage in Rheumatoid Arthritis

Fibroblast-like synoviocytes (FLSs) are important non-immune cells located mostly in the inner layer of the synovium. Indeed, these cells are specialized mesenchymal cells, implicated in collagen homeostasis of the articular joint and provide extracellular matrix (ECM) materials for cartilage and contribute to joint destruction via multiple mechanisms. RA FLS interactions with immune and non-immune cells lead to the development and organization of tertiary structures such as ectopic lymphoid-like structures (ELSs), tertiary lymphoid organs (TLOs), and secretion of proinflammatory cytokines. The interaction of RA FLS cells with immune and non-immune cells leads to stimulation and activation of effector immune cells. Pathological role of RA FLS cells has been reported for many years, while molecular and cellular mechanisms are not completely understood yet. In this review, we tried to summarize the latest findings about the role of FLS cells in ELS formation, joint destruction, interactions with immune and non-immune cells, as well as potential therapeutic options in rheumatoid arthritis (RA) treatment. Our study revealed data about interactions between RA FLS and immune/non-immune cells as well as the role of RA FLS cells in joint damage, ELS formation, and neoangiogenesis, which provide useful information for developing new approaches for RA treatment.

Induced, but not natural, regulatory T cells retain phenotype and function following exposure to inflamed synovial fibroblasts

Aberrant number and/or dysfunction of CD4⁺Foxp3⁺ Regulatory T cells (T_regs) are associated with the pathogenesis of rheumatoid arthritis (RA). A previous study has demonstrated that thymus-derived, natural T_regs (nT_regs) prefer to accumulate in inflamed joints and transdifferentiate to T_H17 cells under the stimulation of inflamed synovial fibroblasts (SFs). In this study, we made a head-to-head comparison of both T_reg subsets and demonstrated that induced T_regs (iT_regs), but not nT_regs, retained Foxp3 expression and regulatory function on T effector cells (T_effs) after being primed with inflamed SFs. In addition, iT_regs inhibited proliferation, inflammatory cytokine production, migration, and invasion ability of collagen-induced arthritis (CIA)-SFs in vitro and in vivo. Moreover, we noted that iT_regs directly targeted inflamed SFs to treat autoimmune arthritis, while nT_regs failed to do this. Thus, manipulation of the iT_reg subset may have a greater potential for prevention or treatment of patients with RA.

Regulatory T cells: A potential weapon to combat COVID-19?

Since the end of December 2019, a novel coronavirus SARS-CoV-2 began to spread, an infection disease termed COVID-19. The virus has spread throughout the world in a short period of time, resulting in a pandemic. The number of reported cases in global reached 5 695 596 including 352 460 deaths, as of May 27, 2020. Due to the lack of effective treatment options for COVID-19, various strategies are being tested. Recently, pathologic studies conducted by two teams in China revealed immunopathologic abnormalities in lung tissue. These results have implications for immunotherapy that could offer a novel therapy strategy for combating lethal viral pneumonia. This review discusses the clinical and pathological features of COVID-19, the roles of immune cells in pathological processes, and the possible avenues for induction of immunosuppressive T regulatory cells attenuating lung inflammation due to viral infection. It is our hope that these proposals may both be helpful in understanding the novel features of SARS-CoV-2 pneumonia as well as providing new immunological strategies for treating the severe sequelae of disease manifestations seen in people infected with SARS-CoV-2.

Inducers, Attractors and Modulators of CD4+ Treg Cells in Non-Small-Cell Lung Cancer

Lung cancer is the leading cause of cancer-associated deaths worldwide, with non-small cell-lung cancer (NSCLC) accounting for approximately 80% of cases. Immune escape has been demonstrated to play a key role in the initiation and progression of NSCLC, although the underlying mechanisms are diverse and their puzzling nature is far from being understood. As a critical participant in immune escape, the CD4⁺ T cell subset of regulatory T (Treg) cells, with their immunosuppressive functions, has been implicated in the occurrence of many types of cancers. Additionally, therapies based on Treg blockade have benefited a portion of cancer patients, including those with NSCLC. Accumulating literature has noted high Treg infiltration in NSCLC tumor tissues, bone marrow, lymph nodes and/or blood; moreover, the tumor milieu is involved in regulating the proliferation, differentiation, recruitment and suppressive functions of Treg cells. Multifarious mechanisms by which CD4⁺ Treg cells are generated, attracted and modulated in the NSCLC milieu will be discussed in this review.

Negligible Effect of Sodium Chloride on the Development and Function of TGF-β-Induced CD4+ Foxp3+ Regulatory T Cells

High-salt diets inhibit the suppressive function of thymus-derived natural regulatory T cells (tTreg). Transforming growth factor β (TGF-β)-induced ex vivo regulatory T cells (iTreg) comprise another Treg subset that exhibits similarities and differences with tTreg. Here, we demonstrate that iTregs are completely stable and fully functional under high salt conditions. High salt does not influence the development, differentiation, and functional activities of iTreg but affects Foxp3 stability and function of tTreg in vitro and in vivo. In addition, high salt does not significantly change the transcription profiles of the iTreg signature or pro-inflammatory genes. Therefore, we conclude that iTreg, unlike tTreg, are stable and functional in the presence of high salt. Our findings provide additional evidence that iTreg may have different biological features from tTreg and suggest a greater potential for clinical utility in patients with autoimmune diseases, in which the complicated role of environmental factors, including diet, must be considered.

Traitor or warrior-Treg cells sneaking into the lesions of psoriatic arthritis

Regulatory T (Treg) cells have been recognized to maintain immune tolerance, which contributes to prevention of autoimmune diseases. However, recent evidence has demonstrated different characteristics of these cells between those that are in circulation compared to those in various local tissues. In addition, the ability of Treg cells to have plasticity in certain disease settings and in inflammatory lesions has been increasingly recognized. Herein we summarize updated knowledge of Treg biology and discuss the current understanding of tissue-resident Treg cells in psoriatic arthritis (PsA), attempting to provide new insights into precise role of Treg cells in the immune response and as a possible therapeutic intervention in patients with PsA.

The progress and prospect of regulatory T cells in autoimmune diseases

Regulatory T cells (Treg) are an important immune cell population, playing a crucial role in regulating immune tolerance and preventing autoimmune diseases. These cells consist of various cell sub-populations and generally have an immunoregulatory or suppressive role against immune responses. They also have a different cell heterogeneity and each populations has own biological characteristics. Treg deficiency, reduction, instability, reduced vitality and dysfunction all account for multiple autoimmune diseases. In this review, we have systemically reviewed Treg classification, phenotypic features, regulation of Foxp3 expression, plasticity and stability of Treg as well as their relationship with several important autoimmune diseases. We particularly focus on why and how inflammatory and diet environments affect the functional capacity and underlying mechanisms of Treg cell populations. We also summarize new advances in technologies which help to analyze and dissect these cells in molecular levels in-depth. We also clarify the possible clinical relevance on application of these cells in patients with autoimmune diseases. The advantages and weaknesses have been carefully discussed as well. We also propose the possible approaches to overcome these weaknesses of Treg cells in complicate environments. Thus, we have displayed the updated knowledge of Treg cells, which provides an overall insight into the role and mechanisms of Treg cells in autoimmune diseases.

Dynamic changes in the regulatory T-cell heterogeneity and function by murine IL-2 mutein

Single-cell RNA-seq analysis reveals that IL-2 mutein treatment expands multiple sub-states of regulatory T cells with superior suppressive function in mice.

The therapeutic expansion of Foxp3⁺ regulatory T cells (Tregs) shows promise for treating autoimmune and inflammatory disorders. Yet, how this treatment affects the heterogeneity and function of Tregs is not clear. Using single-cell RNA-seq analysis, we characterized 31,908 Tregs from the mice treated with a half-life extended mutant form of murine IL-2 (IL-2 mutein, IL-2M) that preferentially expanded Tregs, or mouse IgG Fc as a control. Cell clustering analysis revealed that IL-2M specifically expands multiple sub-states of Tregs with distinct expression profiles. TCR profiling with single-cell analysis uncovered Treg migration across tissues and transcriptional changes between clonally related Tregs after IL-2M treatment. Finally, we identified IL-2M–expanded Tnfrsf9⁺Il1rl1⁺ Tregs with superior suppressive function, highlighting the potential of IL-2M to expand highly suppressive Foxp3⁺ Tregs.

The Role of MicroRNAs in Regulatory T Cells

MicroRNAs are a class of conserved, 20 nt-23 nt long, noncoding small RNAs that inhibit expression of their respective target genes in different cell types. Regulatory T cells (Tregs) are a subpopulation of T cells that negatively regulate immune responses, which is essential to immune homeostasis. Recent studies have indicated that microRNAs play an important role in the proliferation, differentiation, and functions of Treg. Here, we review the recent progress in understanding the roles of microRNAs in Treg and their dysregulation in immune-related diseases. This ongoing research continues to expand the understanding of Treg regulation and the mechanisms of immune disorders.

Reduced activated regulatory T cells and imbalance of Th17/activated Treg cells marks renal involvement in ANCA-associated vasculitis

The role of naturally occurring regulatory T cells (Treg) in the control of the immune tolerance of ANCA-associated vasculitis (AAV) has not been well defined. Therefore, we separate the phenotypically heterogeneous Treg cells into different subsets based on the expression of FOXP3 and CD45RA during AAV pathogenesis. Fifty-four AAV patients (38 patients with renal involvement) and 19 healthy controls (HCs) were enrolled in this study. Levels of CD4⁺T cell subsets and cytokines were detected by flow cytometry. Treg immunesuppression capacity was measured in co-culture experiments. The diagnostic value for Treg subsets was evaluated by the areas under the receiver operating characteristic curves (AUC). Patients with AAV had lower percentages and numbers of activated Treg cells (aTreg, P = 0.044, P = 0.002), while higher levels of total Treg cells (P = 0.001, P = 0.026) with diminished immunosuppression capacity. The proportions of effector memory T-cell subpopulation (P < 0.001) were increased in AAV patients. Interestingly, the AUC of the aTreg improved significantly the diagnostic potential of AAV. Furthermore, the ratio of Th17/aTreg was significantly increased in active and renal vasculitis patient and positive correlation between Th17/Treg subset ratio and creatinine or BUN. In addition, we found that cytokine IL-2 and IL-4 exhibited a downward while IL-6, IL-10, TNF-α, IFN-γ and IL-17A trend upward in AAV patients. Increase in total Treg levels, along with functional deficiency, and decrease in aTreg cells constitute potential novel biomarkers for AAV. And the ratio of Th17/aTreg might serve as an important tool to recognize and monitor AAV patients with renal involvement and disease remission.

Umbilical cord blood transplantation and the impact of the CTLA4 genotype on outcomes

Background: Umbilical cord blood transplantation is an effective method of curing multiple diseases when there is no donor available for allogeneic hematopoietic stem cell transplantation (AHSCT). It has been recently suggested that polymorphisms in genes affecting antigen presentation could potentially affect cord blood transplantation (CBT) outcomes.Areas covered: In this review, we present the results of the latest studies investigating the link between CTLA4 gene variability and umbilical cord blood transplantation outcomes.Expert opinion: The search for genetic variants that influence the immune response, both innate and adaptive immunity, may lead to more optimal therapies. Promising candidate genes are those that regulate the expression of proteins associated with T-cell activation. Many genetic variants could be therapeutically important, including those related to innate and adaptive immunity, cytokines, chemokines, drug-metabolizing enzymes, drug transporters, and inflammatory enzymes. The development of an algorithm that includes the determination of selected genetic variants could be helpful for an appropriate donor-recipient CBT matching.

Prognostic Factors and Biomarkers of Responses to Immune Checkpoint Inhibitors in Lung Cancer

Manipulation of the immune response is a game changer in lung cancer treatment, revolutionizing management. PD1 and CTLA4 are dynamically expressed on different T cell subsets that can either disrupt or sustain tumor growth. Monoclonal antibodies (MoAbs) against PD1/PDL1 and CTLA4 have shown that inhibitory signals can be impaired, blocking T cell activation and function. MoAbs, used as both single-agents or in combination with standard therapy for the treatment of advanced non-small cell lung cancer (NSCLC), have exhibited advantages in terms of overall survival and response rate; nivolumab, pembrolizumab, atezolizumab and more recently, durvalumab, have already been approved for lung cancer treatment and more compounds are in the pipeline. A better understanding of signaling elicited by these antibodies on T cell subsets, as well as identification of biological determinants of sensitivity, resistance and correlates of efficacy, will help to define the mechanisms of antitumor responses. In addition, the relevance of T regulatory cells (Treg) involved in immune responses in cancer is attracting increasing interest. A major challenge for future research is to understand why a durable response to immune checkpoint inhibitors (ICIs) occurs only in subsets of patients and the mechanisms of resistance after an initial response. This review will explore current understanding and future direction of research on ICI treatment in lung cancer and the impact of tumor immune microenvironment n influencing clinical responses.

Engineered Dendritic Cell-Directed Concurrent Activation of Multiple T cell Inhibitory Pathways Induces Robust Immune Tolerance

Inhibitory/repressor-receptors are upregulated significantly on activated T cells, and have been the molecules of attention as targets for inducing immune tolerance. Induction of effective antigen specific tolerance depends on concurrent engagement of the TCR and one or more of these inhibitory receptors. Here, we show, for the first time that dendritic cells (DCs) can be efficiently engineered to express multiple T cell inhibitory ligands, and enhanced engagement of T cell inhibitory receptors, upon antigen presentation, by these DCs can induce effective CD4+ T cell tolerance and suppress autoimmunity. Compared to control DCs, antigen presentation by DCs that ectopically express CTLA4, PD1 and BTLA selective ligands (B7.1wa, PD-L1, and HVEM-CRD1 respectively) individually (mono-ligand DCs) or in combination (multi-ligand DCs) causes an inhibition of CD4+ T cell proliferation and pro-inflammatory cytokine response, as well as increase in Foxp3+ Treg frequency and immune regulatory cytokine production. Administration of self-antigen (mouse thyroglobulin; mTg) loaded multi-ligand DCs caused hyporesponsiveness to mTg challenge, suppression of autoantibody production, and amelioration of experimental autoimmune thyroiditis. Overall, this study shows that engineered DC-directed enhanced concurrent activation of multiple T cell coinhibitory pathways is an effective way to induce self-antigen specific T cell tolerance to suppress ongoing autoimmunity.

The cAMP-Adenosine Feedback Loop Maintains the Suppressive Function of Regulatory T Cells

Therapeutic manipulation of regulatory T cells (Tregs) has been regarded as a promising approach for the treatment of immune disorders. However, a better understanding of the immunomodulatory mechanisms of Tregs and new safe and effective methods to improve the therapeutic effects of Tregs are highly desired. In this study, we have identified the key roles of a cAMP-adenosine positive feedback loop in the immunomodulatory function of Tregs. Adult male C57BL/6J mice were used for an experimental autoimmune uveitis (EAU) model, Tregs, and uveitogenic T cells (UTs). In established EAU, induced Tregs (iTregs) administration alleviated the inflammatory response. In vitro, iTregs inhibited UTs proliferation and inflammatory cytokine production. Mechanistically, cAMP is partially responsible for iTreg-mediated inhibition on UTs. Importantly, intracellular cAMP regulates CD39 expression and CD39-dependent adenosine production in iTregs, and cAMP directly participates in iTreg-derived adenosine production by a CD39 signaling-independent extracellular cAMP-adenosine pathway. Moreover, extracellular adenosine increases the intracellular cAMP level in Tregs. More importantly, increasing the cAMP level in iTregs before transfer improves their therapeutic efficacy in established EAU. Notably, the cAMP-adenosine loop exists in both iTregs and naturally occurring Tregs. These findings provide new insights into the immunosuppressive mechanisms of Tregs and suggest a new strategy for improving the therapeutic efficacy of Tregs in established autoimmune disease.

Immune inhibitory proteins and their pathogenic and therapeutic implications in autoimmunity and autoimmune hepatitis

Key inhibitory proteins can blunt immune responses to self-antigens, and deficiencies in this repertoire may promote autoimmunity. The goals of this review are to describe the key immune inhibitory proteins, indicate their possible impact on the development of autoimmune disease, especially autoimmune hepatitis, and encourage studies to clarify their pathogenic role and candidacy as therapeutic targets. English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed. Cytotoxic T lymphocyte antigen-4 impairs ligation of CD28 to B7 ligands on antigen presenting cells and inhibits the adaptive immune response by increasing anti-inflammatory cytokines, generating regulatory T cells, and reducing T cell activation and proliferation. Programed cell death antigen-1 inhibits T cell selection, activation, and proliferation by binding with two ligands at different phases and locations of the immune response. A soluble alternatively spliced variant of this protein can dampen the inhibitory signal. Autoimmune hepatitis has been associated with polymorphisms of the cytotoxic T lymphocyte antigen-4 gene, reduced hepatic expression of a ligand of programed cell death antigen-1, an interfering soluble variant of this key inhibitory protein, and antibodies against it. Findings have been associated with laboratory indices of liver injury and suboptimal treatment response. Abatacept, belatacept, CD28 blockade, and induction of T cell exhaustion are management considerations that require scrutiny. In conclusion, deficiencies in key immune inhibitory proteins may promote the occurrence of autoimmune diseases, such as autoimmune hepatitis, and emerging interventions may overcome these deficiencies. Investigations should define the nature, impact and management of these inhibitory disturbances in autoimmune hepatitis.

Regulation of Immune Responses and Chronic Inflammation by Fibroblast-Like Synoviocytes

Synovial tissue is a membranous non-immune organ lining joint cavities where it supports local immune responses, and functions directly and indirectly in joint destruction due to chronic inflammatory diseases such as rheumatoid arthritis (RA). Fibroblast-like synoviocytes (FLS), the dominant non-immune cells of synovial tissues, mainly contribute to joint destruction via multiple mechanisms. In RA, FLS respond to endogenous ligands of pattern recognition receptors (PRRs) and inflammatory cytokines as non-immune cells. In addition, FLS aid in the activation of immune responses by interacting with immune cells and by supporting ectopic lymphoid-like structure (ELS) formation in synovial tissues. Moreover, FLS directly cause the pathogenicity of RA i.e., joint deformities. Here, we describe new findings and review the mechanisms underlying the regulation of immune reactions by non-immune FLS and their roles in inflammatory diseases such as RA.

Autologous Hematopoietic Stem Cells Are a Preferred Source to Generate Dendritic Cells for Immunotherapy in Multiple Myeloma Patients

In multiple myeloma (MM), dendritic cells (DCs), and their precursors are prone to malignant cell-mediated regulation of function leading to low efficacy of DC vaccine. DCs taken directly from MM patient's body or derived from monocytes are fewer in numbers and are also dysfunctional. Here, we investigated the functionality of Hematopoietic stem cell-derived DCs (SC-DCs) from MM patients. Mature-MM-SC-DCs showed all essential functions like antigen uptake, allogenic T cells simulation and migration comparable to those derived from healthy donor (HD) samples. A comparison of Mo-DCs and SC-DCs obtained from the same MM patients' samples revealed that the expression of IL-6 was higher in the precursors of Mo-DCs leading to their impaired migration. In addition, expression of CCR7 which is responsible for DCs migration was found to be lower in MM-Mo-DCs. The chromatin permissiveness as observed by H3K4me³ histone modification at the Ccr7 promoter in MM-Mo-DCs was significantly lower than those in MM-SC-DCs. Levels of Zbtb46- a hall mark DC transcription factor mRNA was also found to be reduced in MM-Mo-DCs. Cytotoxic T cells generated from MM-SC-DCs from autologous naïve T cells exhibited reduced antitumor activity because the T cells were exhausted. Blocking of CTLA-4 on autologous T cells could partially restore T cell proliferation and activation. Thus, a combination of MM-SC-DC vaccine and anti-CTLA-4 antibody may serve as a better candidate for immunotherapy of MM. This study has implications in increasing the efficacy of cancer immunotherapy in MM.

Helios but not CD226, TIGIT and Foxp3 is a Potential Marker for CD4+ Treg Cells in Patients with Rheumatoid Arthritis

BACKGROUND/AIMS

Rheumatoid arthritis (RA) is a progressive, chronic, even disabling systemic autoimmune disease. Imbalance between pathogenic immune cells and immunosuppressive cells is associated with the pathogenesis and development of RA and other autoimmune diseases. As Foxp3 is also expressed on activated CD4⁺ cells in the presence of inflammation, the identification of Treg cells in patients with RA remains a challenge.

METHODS

Comprehensive analyses were carried out by Flow cytometry. Expression of Helios, CD226, T cell immunoreceptor with Ig and ITIM domains clinical samples and healthy controls.

RESULTS

We have systemically examined three potential markers, Helios, CD226 and TIGIT, that are possibly related to Treg identification, and found that Helios expression on CD4⁺Foxp3⁺cells was decreased and negatively correlated with the disease activity of RA patients, while CD226 and TIGIT both showed elevated expression levels in CD4⁺Foxp3⁺cells in RA patients and they were not associated with disease activity of RA patients.

CONCLUSION

Taken together, our findings indicate that CD4⁺CD25^hiCD127^low/-Foxp3⁺Helios⁺ may represent the real Treg cell population in patients with RA.

The essential role of costimulatory molecules in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic inflammatory disease with immune system disorder mediated through complex autoimmune pathways that involve immune cells, nonimmune cells, cytokines, chemokines, as well as costimulatory molecules. Costimulatory signals play a critical role in initiating, maintaining and regulating immune reactions, and these include ligands and receptors and their interactions involving multiple types of signal information. Dysfunction of costimulatory factors results in complicated abnormal immune responses, with biological effects and eventually, clinical autoimmune diseases. Here we outline what is known about various roles that costimulatory families including the B7 family and tumor necrosis factor super family play in SLE. The aim of this review is to understand the possible association of costimulation with autoimmune diseases, especially SLE, and to explore possible therapeutic target(s) of costimulatory molecules and pathways that might be used to develop therapeutic approaches for patients with these conditions.

Aquaporin-4 deficiency reduces TGF-β1 in mouse midbrains and exacerbates pathology in experimental Parkinson's disease

Aquaporin-4 (AQP4), the main water-selective membrane transport protein in the brain, is localized to the astrocyte plasma membrane. Following the establishment of a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease (PD) model, AQP4-deficient (AQP4^-/- ) mice displayed significantly stronger microglial inflammatory responses and remarkably greater losses of tyrosine hydroxylase (TH⁺ )-positive neurons than did wild-type AQP4 (AQP4^+/+ ) controls. Microglia are the most important immune cells that mediate immune inflammation in PD. However, recently, few studies have reported why AQP4 deficiency results in more severe hypermicrogliosis and neuronal damage after MPTP treatment. In this study, transforming growth factor-β1 (TGF-β1), a key suppressive cytokine in PD onset and development, failed to increase in the midbrain and peripheral blood of AQP4^-/- mice after MPTP treatment. Furthermore, the lower level of TGF-β1 in AQP4^-/- mice partially resulted from impairment of its generation by astrocytes; reduced TGF-β1 may partially contribute to the uncontrolled microglial inflammatory responses and subsequent severe loss of TH⁺ neurons in AQP4^-/- mice after MPTP treatment. Our study provides not only a better understanding of both aetiological and pathogenical factors implicated in the neurodegenerative mechanism of PD but also a possible approach to developing new treatments for PD via intervention in AQP4-mediated immune regulation.

CD71+VISTA+ erythroid cells promote the development and function of regulatory T cells through TGF-β

Cell-surface transferrin receptor (CD71⁺) erythroid cells are abundant in newborns with immunomodulatory properties. Here, we show that neonatal CD71⁺ erythroid cells express significant levels of V-domain Immunoglobulin (Ig) Suppressor of T Cell Activation (VISTA) and, via constitutive production of transforming growth factor (TGF)- β, play a pivotal role in promotion of naïve CD4⁺ T cells into regulatory T cells (Tregs). Interestingly, we discovered that CD71⁺VISTA⁺ erythroid cells produce significantly higher levels of TGF-β compared to CD71⁺VISTA⁻ erythroid cells and CD71⁺ erythroid cells from the VISTA knock-out (KO) mice. As a result, CD71⁺VISTA⁺ erythroid cells—compared to CD71⁺VISTA⁻ and CD71⁺ erythroid cells from the VISTA KO mice—significantly exceed promotion of naïve CD4⁺ T cells into induced Tregs (iTreg) via TGF-β in vitro. However, depletion of CD71⁺ erythroid cells had no significant effects on the frequency of Tregs in vivo. Surprisingly, we observed that the remaining and/or newly generated CD71⁺ erythroid cells following anti-CD71 antibody administration exhibit a different gene expression profile, evidenced by the up-regulation of VISTA, TGF-β1, TGF-β2, and program death ligand-1 (PDL-1), which may account as a compensatory mechanism for the maintenance of Treg population. We also observed that iTreg development by CD71⁺ erythroid cells is mediated through the inhibition of key signaling molecules phosphorylated protein kinase B (phospho-Akt) and phosphorylated mechanistic target of rapamycin (phospho-mTOR). Finally, we found that elimination of Tregs using forkhead box P3 (FOXP3)-diptheria toxin receptor (DTR) mice resulted in a significant expansion in the frequency of CD71⁺ erythroid cells in vivo. Collectively, these studies provide a novel, to our knowledge, insight into the cross-talk between CD71⁺ erythroid cells and Tregs in newborns. Our results highlight the biological role of CD71⁺ erythroid cells in the neonatal period and possibly beyond.

The primary role of the red blood cells is to transport oxygen, but we know relatively little about the other functions they perform. Following maturation, red blood cells exit the bone marrow and enter blood circulation. Their immature counterparts are normally absent or in very low frequency in the blood of healthy adults. However, we showed previously that immature red blood cells are abundant in the spleens of neonatal mice and in human umbilical cord blood and that these cells possess immunological properties. In this report, we studied a subset of neonatal immature red blood cells that express a protein called V-domain Immunoglobulin (Ig) Suppressor of T Cell Activation (VISTA) on their surface. We found that the presence of VISTA enables the cells to repeatedly produce the regulatory cytokine TGF-β. TGF-β induces a subset of naïve lymphocytes—the CD4⁺ T cells—and converts them into regulatory T cells, also known as Tregs. Tregs modulate and suppress other immune cells. Our studies provide novel insights, to our knowledge, into the immunological role of immature red blood cells in newborns.