Natural and TGF-β–induced Foxp3+CD4+ CD25+ regulatory T cells are not mirror images of each other

Role of regulatory T cells in inflammatory liver diseases

The liver is the human body's largest digestive gland, which can participate in digestion, metabolism, excretion, detoxification and immunity. Chronic liver diseases such as metabolic dysfunction-associated fatty liver disease (MAFLD) or viral hepatitis involve ongoing inflammation and resulting liver fibrosis may ultimately lead to the development of hepatobiliary cancers (HCC). Inflammation is the coordinated reaction of different liver cell types to cell signals and death of inflammation, which are linked to injury pathways within the liver or external agents from the gut-liver axis and the circulation. Regulatory T (Treg) cells play a crucial role in controlling inflammation and are essential for maintaining immune tolerance and balance. In this review, we highlight the recent discoveries related to the function of immune systems in liver inflammation and discuss the role of Treg cells in the different liver diseases (including MAFLD, autoimmune hepatitis and others).

Autoimmune effector mechanisms associated with a defective immunosuppressive axis in immune thrombocytopenia (ITP)

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by an isolated thrombocytopenia and variable phenotype as some patients suffer no bleeding whilst others have bleeding from mild to severe, which may be fatal. This variability probably reflects the disease's complex pathophysiology; a dysregulated hyperreactive immune effector cell response involving the entire adaptive immune system (e.g. B and T cell subsets) that leads to platelet and megakaryocyte (MK) destruction. It appears that these effector responses are due to a breakdown in immune tolerance, and this is characterized by defects in several immunosuppressive cell types. These include defective T regulatory cells (Tregs), B regulatory cells (Bregs) and Myeloid-derived suppressor cells (MDSC), all of which are all intimately associated with antigen presenting cells (APC) such as dendritic cells (DC). The loss of this immunosuppressive axis allows for the activation of unchecked autoreactive T cells and B cells, leading to the development of autoantibodies and cytotoxic T cells (CTL), which can directly destroy platelets in the periphery and inhibit MK platelet production in the bone marrow (BM). This review will focus on the effector cell mechanisms in ITP and highlight the defective immunosuppressive axis that appears responsible for this platelet-specific immune hyperreactivity.

Treg Cell Therapeutic Strategies for Breast Cancer: Holistic to Local Aspects

Regulatory T cells (Tregs) play a key role in maintaining immune homeostasis and preventing autoimmunity through their immunosuppressive function. There have been numerous reports confirming that high levels of Tregs in the tumor microenvironment (TME) are associated with a poor prognosis, highlighting their role in promoting an immunosuppressive environment. In breast cancer (BC), Tregs interact with cancer cells, ultimately leading to the suppression of immune surveillance and promoting tumor progression. This review discusses the dual role of Tregs in breast cancer, and explores the controversies and therapeutic potential associated with targeting these cells. Researchers are investigating various strategies to deplete or inhibit Tregs, such as immune checkpoint inhibitors, cytokine antagonists, and metabolic inhibition. However, the heterogeneity of Tregs and the variable precision of treatments pose significant challenges. Understanding the functional diversity of Tregs and the latest advances in targeted therapies is critical for the development of effective therapies. This review highlights the latest approaches to Tregs for BC treatment that both attenuate Treg-mediated immunosuppression in tumors and maintain immune tolerance, and advocates precise combination therapy strategies to optimize breast cancer outcomes.

Controlled WASp activity regulates the proliferative response for Treg cell differentiation in the thymus

The Wiskott-Aldrich syndrome protein (WASp) regulates actin cytoskeletal dynamics and function of hematopoietic cells. Mutations in the WAS gene lead to two different syndromes; Wiskott-Aldrich syndrome (WAS) caused by loss-of-function mutations, and X-linked neutropenia (XLN) caused by gain-of-function mutations. We previously showed that WASp-deficient mice have a decreased number of regulatory T (Treg) cells in the thymus and the periphery. We here evaluated the impact of WASp mutations on Treg cells in the thymus of WAS and XLN mouse models. Using in vitro Treg differentiation assays, WAS CD4 single-positive thymocytes have decreased differentiation to Treg cells, despite normal early signaling upon IL-2 and TGF-β stimulation. They failed to proliferate and express CD25 at high levels, leading to poor survival and a lower number of Foxp3+ Treg cells. Conversely, XLN CD4 single-positive thymocytes efficiently differentiate into Foxp3+ Treg cells following a high proliferative response to IL-2 and TGF-β, associated with high CD25 expression when compared with WT cells. Altogether, these results show that specific mutations of WASp affect Treg cell development differently, demonstrating a critical role of WASp activity in supporting Treg cell development and expansion.

Targeting tumor-infiltrating tregs for improved antitumor responses

Immunotherapies have revolutionized the landscape of cancer treatment. Regulatory T cells (Tregs), as crucial components of the tumor immune environment, has great therapeutic potential. However, nonspecific inhibition of Tregs in therapies may not lead to enhanced antitumor responses, but could also trigger autoimmune reactions in patients, resulting in intolerable treatment side effects. Hence, the precision targeting and inhibition of tumor-infiltrating Tregs is of paramount importance. In this overview, we summarize the characteristics and subpopulations of Tregs within tumor microenvironment and their inhibitory mechanisms in antitumor responses. Furthermore, we discuss the current major strategies targeting regulatory T cells, weighing their advantages and limitations, and summarize representative clinical trials targeting Tregs in cancer treatment. We believe that developing therapies that specifically target and suppress tumor-infiltrating Tregs holds great promise for advancing immune-based therapies.

Classification of regulatory T cells and their role in myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MIRI) is closely related to the final infarct size in acute myocardial infarction (AMI). Therefore, reducing MIRI can effectively improve the prognosis of AMI patients. At the same time, the healing process after AMI is closely related to the local inflammatory microenvironment. Regulatory T cells (Tregs) can regulate various physiological and pathological immune inflammatory responses and play an important role in regulating the immune inflammatory response after AMI. However, different subtypes of Tregs have different effects on MIRI, and the same subtype of Tregs may also have different effects at different stages of MIRI. This article systematically reviews the classification and function of Tregs, as well as the role of various subtypes of Tregs in MIRI. A comprehensive understanding of the role of each subtype of Tregs can help design effective methods to control immune reactions, reduce MIRI, and provide new potential therapeutic options for AMI.

Immunomodulatory effects of canine mesenchymal stem cells in an experimental atopic dermatitis model

Mesenchymal stem cells (MSCs) have the potential to differentiate into multi-lineage cells, suggesting their future applicability in regenerative medicine and biotechnology. The immunomodulatory properties of MSCs make them a promising replacement therapy in various fields of animal research including in canine atopic dermatitis (AD), a skin disease with 10-15% prevalence. We investigated the immunomodulatory effects of MSCs in an experimental canine AD model induced by Dermatophagoides farinae extract ointment. Canine adipose tissue-derived MSCs (cAT-MSCs) were differentiated into mesodermal cell lineages at the third passage. Alterations in immunomodulatory factors in control, AD, and MSC-treated AD groups were evaluated using flow cytometric analysis, enzyme-linked immunosorbent assay, and quantitative reverse transcription PCR. In the MSC-treated AD group, the number of eosinophils decreased, and the number of regulatory T cells (Tregs) increased compared to those in the AD group. In addition, the immunoglobulin E (IgE) and prostaglandin E₂ levels were reduced in the MSC-treated AD group compared to those in the AD group. Furthermore, the filaggrin, vascular endothelial growth factor, and interleukin-5 gene expression levels were relatively higher in the MSC-treated AD group than in the AD group, however, not significantly. cAT-MSCs exerted immunomodulatory effects in an AD canine model via a rebalancing of type-1 and -2 T helper cells that correlated with increased levels of Tregs, IgE, and various cytokines.

Immune Response and Molecular Mechanisms of Cardiovascular Adverse Effects of Spike Proteins from SARS-CoV-2 and mRNA Vaccines

The SARS-CoV-2 (severe acute respiratory syndrome coronavirus responsible for the COVID-19 disease) uses the Spike proteins of its envelope for infecting target cells expressing on the membrane the angiotensin converting enzyme 2 (ACE2) enzyme that acts as a receptor. To control the pandemic, genetically engineered vaccines have been designed for inducing neutralizing antibodies against the Spike proteins. These vaccines do not act like traditional protein-based vaccines, as they deliver the message in the form of mRNA or DNA to host cells that then produce and expose the Spike protein on the membrane (from which it can be shed in soluble form) to alert the immune system. Mass vaccination has brought to light various adverse effects associated with these genetically based vaccines, mainly affecting the circulatory and cardiovascular system. ACE2 is present as membrane-bound on several cell types, including the mucosa of the upper respiratory and of the gastrointestinal tracts, the endothelium, the platelets, and in soluble form in the plasma. The ACE2 enzyme converts the vasoconstrictor angiotensin II into peptides with vasodilator properties. Here we review the pathways for immunization and the molecular mechanisms through which the Spike protein, either from SARS-CoV-2 or encoded by the mRNA-based vaccines, interferes with the Renin-Angiotensin-System governed by ACE2, thus altering the homeostasis of the circulation and of the cardiovascular system. Understanding the molecular interactions of the Spike protein with ACE2 and the consequent impact on cardiovascular system homeostasis will direct the diagnosis and therapy of the vaccine-related adverse effects and provide information for development of a personalized vaccination that considers pathophysiological conditions predisposing to such adverse events.

COVID-19 immunotherapy: Treatment based on the immune cell-mediated approaches

Multiple efforts are currently underway to control and treat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus disease 2019 (COVID-19) worldwide. Despite all efforts, the virus that emerged in Wuhan city has rapidly spread globally and led to a public health emergency of international concern (PHEIC) due to the lack of approved antiviral therapy. Nevertheless, SARS-CoV-2 has had a significant influence on the evolution of cellular therapeutic approaches. Adoptive immune cell therapy is innovative and offers either promising prophylactic or therapy for patients with moderate-to-severe COVID-19. This approach is aimed at developing safety and providing secure and effective therapy in combination with standard therapy for all COVID-19 infected individuals. Based on the effective results of previous studies on both inflammatory and autoimmune diseases, various immune cell therapies against COVID-19 have been reviewed and discussed. It must be considered that the application of cell therapy for treatment and to eliminate infected respiratory cells could result in excessive inflammation, so this treatment must be used in combination with other treatments, despite its many beneficial efforts.

Regulatory T-Cells and Multiple Myeloma: Implications in Tumor Immune Biology and Treatment

Multiple myeloma (MM) is associated with both cellular and humoral immune deficiencies and, despite significant advances in treatment, remains an incurable disease. Regulatory T-cells (Tregs) represent a critical subset of CD4 T-cells, characterized by CD4 + CD25+ Forkhead box P3+ (FoxP3+) phenotype, able to control peripheral tolerance and responses to foreign and tumor antigens. Tregs are elevated in various types of cancer, including hematological malignancies; in MM, data regarding Tregs function and numbers and their correlation with survival parameters are controversial. Advances in cancer biology have shown that the tumor microenvironment plays an important role in tumor progression. In MM, the highly immunosuppressive nature of the bone marrow microenvironment has been significantly elucidated in the past decade and it is now well acknowledged that targeting only the tumor clone may not be able to cure MM. Tregs within the tumor microenvironment might play a significant role in the suppression of antitumor immune responses against cancer cells and are considered to predict poor outcome in cancer patients; nonetheless the exact prognostic significance of this cell subpopulation in malignancies is still a matter of debate. In this review, we discuss the role of Tregs as an essential cell population of the MM immune microenvironment.

Multiply restimulated human thymic regulatory T cells express distinct signature regulatory T-cell transcription factors without evidence of exhaustion

BACKGROUND AIMS

Adoptive transfer of suppressive CD4+CD25+ thymic regulatory T cells (tTregs) can control auto- and alloimmune responses but typically requires in vitro expansion to reach the target cell number for efficacy. Although the adoptive transfer of expanded tTregs purified from umbilical cord blood ameliorates graft-versus-host disease in patients receiving hematopoietic stem cell transplantation for lymphohematopoietic malignancy, individual Treg products of 100 × 106 cells/kg are manufactured over an extended 19-day time period using a process that yields variable products and is both laborious and costly. These limitations could be overcome with the availability of 'off the shelf' Treg.

RESULTS

Previously, the authors reported a repetitive restimulation expansion protocol that maintains Treg phenotype (CD4+25++127-Foxp3+), potentially providing hundreds to thousands of patient infusions. However, repetitive stimulation of effector T cells induces a well-defined program of exhaustion that leads to reduced T-cell survival and function. Unexpectedly, the authors found that multiply stimulated human tTregs do not develop an exhaustion signature and instead maintain their Treg gene expression pattern. The authors also found that tTregs expanded with one or two rounds of stimulation and tTregs expanded with three or five rounds of stimulation preferentially express distinct subsets of a group of five transcription factors that lock in Treg Foxp3expression, Treg stability and suppressor function. Multiply restimulated Tregs also had increased transcripts characteristic of T follicular regulatory cells, a Treg subset.

DISCUSSION

These data demonstrate that repetitively expanded human tTregs have a Treg-locking transcription factor with stable FoxP3 and without the classical T-cell exhaustion gene expression profile-desirable properties that support the possibility of off-the-shelf Treg therapeutics.

Comparison of clinical outcomes and FOXP3, IL-17A responses in Helicobacter pylori infection in children versus adults

BACKGROUND

The purpose of this study was to compare the clinical symptoms and pathological consequences of Helicobacter pylori (H. pylori) infection between children and adults and determine the levels of expression of FOX3P and IL-17A to examine the Th17/Treg balance.

METHODS

Forty pediatric and 40 adult patients who were followed up at the Pediatric Gastroenterology and Internal Medicine Gastroenterology Departments were enrolled in the study. In our case-control study, gastric tissue specimens were evaluated using the updated Sydney system, and the number of cells expressing FOXP3/IL-17A (T_reg and Th17 cell markers) was analyzed immunohistochemically. In addition, each case was evaluated using a clinical follow-up questionnaire.

RESULTS

Clinical signs and symptoms of children and adults were similar. IL-17A and FOXP3 levels were significantly higher in children and adults with H. pylori (+) than in those without H. pylori (-) (p < .001). In patients with H. pylori (+), the mean FOXP3 level was significantly higher, whereas the mean IL-17A level was significantly lower in children than in adults (p < 0001 for both groups). In children with H. pylori (+), bacterial density was negatively correlated with IL-17A level and positively correlated with FOXP3 level. In adults with H. pylori (+), there was a statistically significant, highly positive correlation between bacterial density and levels of IL-17A and FOXP3.

CONCLUSIONS

T_reg cells are suggested to more predominant in children than in adults, IL-17A levels decrease as H. pylori bacterial density increases. In conclusion, immune responses incline toward T_reg , which increases the susceptibility to persistent infections.

Immunosuppression as a Hallmark of Critical COVID-19: Prospective Study

The dysregulation of both the innate and adaptive responses to SARS-CoV-2 have an impact on the course of COVID-19, and play a role in the clinical outcome of the disease. Here, we performed a comprehensive analysis of peripheral blood lymphocyte subpopulations in 82 patients with COVID-19, including 31 patients with a critical course of the disease. In COVID-19 patients who required hospitalization we analyzed T cell subsets, including Treg cells, as well as TCRα/β and γ/δ, NK cells, and B cells, during the first two weeks after admission to hospital due to the SARS-CoV-2 infection, with marked reductions in leukocytes subpopulations, especially in critically ill COVID-19 patients. We showed decreased levels of Th, Ts cells, Treg cells (both naïve and induced), TCRα/β and γ/δ cells, as well as CD16+CD56+NK cells in ICU compared to non-ICU COVID-19 patients. We observed impaired function of T and NK cells in critically ill COVID-19 patients with extremely low levels of secreted cytokines. We found that the IL-2/INFγ ratio was the strongest indicator of a critical course of COVID-19, and was associated with fatal outcomes. Our findings showed markedly impaired innate and adaptive responses in critically ill COVID-19 patients, and suggest that the immunosuppressive state in the case of a critical course of SARS-CoV-2 infection might reflect subsequent clinical deterioration and predict a fatal outcome.

Association of CTLA-4 (+49 A/G) polymorphism with susceptibility to autoimmune diseases: A meta-analysis with trial sequential analysis

OBJECTIVES

In recent years, more and more studies have been focusing on the association between Cytotoxic T lymphocyte antigen-4 (CTLA-4) (+49 A/G) gene polymorphism and autoimmune diseases. However, the results of previous studies are still controversial. The meta-analysis is aiming at determining the association in CTLA-4 (+49 A/G) gene rs231775 polymorphism and ankylosing spondylitis (AS), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE).

METHODS

We searched PubMed, Web of Science, Chinese National Knowledge Infrastructure (CNKI) and Chinese Biomedical Database (CBM) up to November 2020, use random or fixed-effect models to perform meta-analysis to compare alleles and other genetic models, including homozygous, heterozygous, recessive and dominant models. The odds ratio (OR) with a 95% confidence interval (95% CI) was used to assess the correlation between CTLA-4 (+49 A/G) gene polymorphism and the genetic affectability of AS, RA, and SLE. Meanwhile, we used sequential trial analysis (TSA) to analyze the reliability of the results. Finally, we searched the relevant data of genome-wide association studies (GWAS) to further verify the accuracy of the experimental results.

RESULTS

47 studies with 11,893 cases and 12,032 healthy controls were included. The rs231775 G allele was relevant to high risk of autoimmune disease over all people (P < 0.05). The G allele of rs231775 was significantly related to RA susceptibility (P < 0.05), but not with AS or SLE. Subgroup analysis by ethnicity indicated that rs231775 G allele was closely related to RA in Caucasian populations and Mongolian populations (P < 0.05). A strong connection within rs231775 G allele and AS affectability was uncovered in Caucasian populations (P < 0.05). The analysis of the TSA shows that the meta-analysis can draw the conclusion.

CONCLUSION

CTLA-4 (+49 A/G) gene rs231775 G allele increases the risk of autoimmune diseases in Caucasian populations. And it also increases the risk of RA in Caucasian and Mongolian populations. More sample size and more elaborately designed studies are needed to elucidate the relationship in CTLA-4 (+49 A/G) gene rs231775 G allele and autoimmune diseases, especially AS, SLE.

Immunomodulatory Function of Vitamin D and Its Role in Autoimmune Thyroid Disease

Vitamin D is one of the most important nutrients required by the human body. It is a steroid hormone that plays an important role in regulating calcium and phosphorus metabolism, and bone health. Epidemiological studies have revealed a close correlation between vitamin D and many common chronic diseases. Additionally, vitamin D has recently been shown to act as an immunomodulatory hormone, and, accordingly, vitamin D deficiency was uncovered as a risk factor for autoimmune thyroid diseases, although the underlying mechanisms are still unknown. It is therefore necessary to disclose the role and mechanism of action of vitamin D in the occurrence and development of autoimmune thyroid diseases. This knowledge will help design intervention and early treatment strategies for patients with autoimmune thyroid diseases who present with low levels of vitamin D.

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.

Induced regulatory T cells suppress Tc1 cells through TGF-β signaling to ameliorate STZ-induced type 1 diabetes mellitus

Type 1 diabetes mellitus (T1D) is a chronic autoimmune condition in which the immune system destroys insulin-producing pancreatic β cells. In addition to well-established pathogenic effector T cells, regulatory T cells (Tregs) have also been shown to be defective in T1D. Thus, an increasing number of therapeutic approaches are being developed to target Tregs. However, the role and mechanisms of TGF-β-induced Tregs (iTregs) in T1D remain poorly understood. Here, using a streptozotocin (STZ)-induced preclinical T1D mouse model, we found that iTregs could ameliorate the development of T1D and preserve β cell function. The preventive effect was associated with the inhibition of type 1 cytotoxic T (Tc1) cell function and rebalancing the Treg/Tc1 cell ratio in recipients. Furthermore, we showed that the underlying mechanisms were due to the TGF-β-mediated combinatorial actions of mTOR and TCF1. In addition to the preventive role, the therapeutic effects of iTregs on the established STZ-T1D and nonobese diabetic (NOD) mouse models were tested, which revealed improved β cell function. Our findings therefore provide key new insights into the basic mechanisms involved in the therapeutic role of iTregs in T1D.

CELL THERAPY IN INFLAMMATORY BOWEL DISEASE

In recent years, cell-based therapies have been explored in various immune-mediated inflammatory diseases, including inflammatory bowel disease (IBD). Cell therapy is the process of introducing new cells into an organism or tissue in order to treat a disease. The most studied cellular treatment in IBD was "stem cells-based therapy", which was explored according to different protocols in terms of type of donors, stem cells sources, study design and clinical endpoints. More recently, preliminary studies have also described the clinical use of "regulatory cells", which include T-reg and Tr1 cells, and "tolerogenic" dendritic cells. Finally, induced pluripotent stem cells are the subject of an intensive preclinical research program on animal models, including those related to colitis.

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.

Role of regulatory T cells in psoriasis pathogenesis and treatment

Psoriasis is a chronic inflammatory disease with a strong genetic component that can be triggered by environmental factors. Disease pathogenesis is mainly driven by type 1 and type 17 cytokine-producing cells which, in healthy individuals, are modulated by regulatory T cells (Tregs). Tregs play a fundamental role in immune homeostasis and contribute to the prevention of autoimmune disease by suppressing immune responses. In psoriasis, Tregs are impaired in their suppressive function leading to an altered T-helper 17/Treg balance. Although Treg dysfunction in patients with psoriasis is associated with disease exacerbation, it is unknown how they are functionally regulated. In this review, we discuss recent insights into Tregs in the setting of psoriasis with an emphasis on the effect of current treatments on Tregs and how already available therapeutics that modulate Treg frequency or functionality could be exploited for treatment of psoriasis.

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.

The Association of Gut Microbiota and Treg Dysfunction in Autoimmune Diseases

Autoimmune conditions affect 23 million Americans or 7% of the US population. There are more than 100 autoimmune disorders, affecting every major organ system in humans. This chapter aims to further explain Treg dysfunction autoimmune disorders, including monogenic primary immune deficiency such as immune dysregulation polyendocrinopathy, enteropathy, X-linked inheritance (IPEX) syndrome, and polygenic autoimmune diseases with Treg dysfunction such as multiple sclerosis (MS), inflammatory bowel disease (IBD), and food allergy. These conditions are associated with an abnormal small intestinal and colonic microbiome. Some disorders clearly improve with therapies aimed at microbial modification, including probiotics and fecal microbiota transplantation (FMT). Approaches to prevent and treat these disorders will need to focus on the acquisition and maintenance of a healthy colonic microbiota, in addition to more focused approaches at immune suppression during acute disease exacerbations.

Regulatory T Cells: Concept, Classification, Phenotype, and Biological Characteristics

Regulatory T cells (Treg) play an indispensable role in maintaining the body's immune nonresponse to self-antigens and suppressing the body's unwarranted and potentially harmful immune responses. Their absence, reduction, dysfunction, transformation, and instability can lead to numerous autoimmune diseases. There are several distinct subtypes of the Treg cells, although they share certain biological characteristics and have unique phenotypes with different regulatory functions, as well as mechanistic abilities. In this book chapter, we introduce the latest advances in Treg cell subtypes pertaining to classification, phenotype, biological characteristics, and mechanisms. We also highlight the relationship between Treg cells and various diseases, including autoimmune, infectious, as well as tumors and organ transplants.

An updated advance of autoantibodies in autoimmune diseases

Autoantibodies are abnormal antibodies which are generated by pathogenic B cells when targeting an individual's own tissue. Autoantibodies have been identified as a symbol of autoimmune disorders and are frequently considered a clinical marker of these disorders. Autoimmune diseases, including system lupus erythematosus and rheumatoid arthritis, consist of a series of disorders that share some similarities and differences. They are characterized by chronic, systemic, excessive immune activation and inflammation and involve in almost all body tissues. Autoimmune diseases occur more frequently in women than men due to hormonal impacts. In this review we systemically introduce and summarize the latest advances of various autoantibodies in multiple autoimmune diseases.

Activin A Promotes Regulatory T-cell-Mediated Immunosuppression in Irradiated Breast Cancer

Increased regulatory T cells (Treg) after radiotherapy have been reported, but the mechanisms of their induction remain incompletely understood. TGFβ is known to foster Treg differentiation within tumors and is activated following radiotherapy. Thus, we hypothesized that TGFβ blockade would result in decreased Tregs within the irradiated tumor microenvironment. We found increased Tregs in the tumors of mice treated with focal radiotherapy and TGFβ blockade. This increase was mediated by upregulation of another TGFβ family member, activin A. In vitro, activin A secretion was increased following irradiation of mouse and human breast cancer cells, and its expression was further enhanced upon TGFβ blockade. In vivo, dual blockade of activin A and TGFβ was required to decrease intratumoral Tregs in the context of radiotherapy. This resulted in an increase in CD8⁺ T-cell priming and was associated with a reduced tumor recurrence rate. Combination of immune checkpoint inhibitors with the dual blockade of activin A and TGFβ led to the development of tumor-specific memory responses in irradiated breast cancer. Supporting the translational value of activin A targeting to reduce Treg-mediated immunosuppression, retrospective analysis of a public dataset of patients with breast cancer revealed a positive correlation between activin A gene expression and Treg abundance. Overall, these results shed light on an immune escape mechanism driven by activin A and suggest that dual targeting of activin A and TGFβ may be required to optimally unleash radiation-induced antitumor immunity against breast cancer.

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.

CD4+CD126low/- Foxp3+ Cell Population Represents a Superior Subset of Regulatory T Cells in Treating Autoimmune Diseases

CD4⁺Foxp3⁺ regulatory T (Treg) cells are crucial for maintaining homeostasis and preventing autoimmune diseases. Nonetheless, we and others have previously reported that natural Treg cells are unstable and dysfunctional in the inflamed environment with a high-salt diet, limiting the Treg function in disease control. In this study, we made an innovative observation showing a high degree of heterogeneity within the Treg pool. We identified that CD126, interleukin (IL)-6 receptor alpha chain, contributed to Treg cell instability. Using a series of in vitro and in vivo experimental approaches, we demonstrated that CD126^Lo/- Treg cells presented greater function and were more stable than CD126^Hi nTreg cells, even in the presence of IL-6 and inflammation. Blockade of programmed death-1 (PD-1) interrupted CD126^Lo/- nTreg cell stability. Additionally, CD126^Lo/- Treg cells can treat colitis and established collagen-induced arthritis, while the CD126^Hi cell population failed to do this. Moreover, we noted that CD126 expression of Treg cells had a positive correlation to rheumatoid arthritis (RA) severity and the stability of Treg cells. Our results strongly suggest that the manipulation of CD126^Lo/- nTreg cells could be a novel strategy for the treatment of autoimmune diseases and for other conditions associated with a deficit of Treg cells.

Type 2 inflammation suppression by T-regulatory cells attenuates the eosinophil recruitment in mucosa of chronic sinusitis

Type 2 inflammation and eosinophilic infiltration are prominent pathologic features of chronic rhinosinusitis with nasal polyps (CRSwNP). The purpose of the present study was to determine the roles of Tregs in controlling type 2 inflammation and inhibiting eosinophilic infiltration in CRSwNP. A total of 134 nasal polyps, 67 ostiomeatal complex from chronic rhinosinusitis (CRS) and 62 normal nasal tissues from controls were collected to study the enumeration and function of Tregs cells and the expressions of cytokine profiles via immunofluorescence staining, flow cytometry, qRT-PCR, ELISA, and/or H&E staining. The effects of Tregs on type2 and type3 inflammations were determined in an eosinophilic chronic sinusitis (ECRS) mice model. It was confirmed that the CRSwNP displayed the features of Th2 and Th17 cells-mediated inflammation, accompanying by an increased level of eosinophilic infiltration and the eosinophil cationic protein (ECP), with a decreased frequency of Treg cells. Furthermore, the percentages of CD4+CD25+CD127lowTreg and CD4+CD25+Foxp3+Treg were only decreased in the polyps of CRSwNP but not in the paired peripheral blood. The CRSwNP possessed the decreased Nrp1+Tregs, Helios+Treg, and low TGF-β and interleukin (IL)-10 expressions in Tregs. The ECRS mice showed similar inflammatory characteristics to CRSwNP patients. The adoptive transfer of CD4+CD25+Foxp3+ Treg cells significantly decreased the inflammatory cytokines, eosinophilic chemotactic factors in the mucosa of the ECRS mice without alteration of the immune balance in the peripheral blood and spleen. In conclusion, CRSwNP showed high type 2 and type3 inflammation and defective Tregs. The induced regulatory T cell (iTreg) may correct the imbalance between immune tolerance and effect via limiting the eosinophil recruitment of mucosa in CRSwNP.

Comparative Study of Immunomodulatory Agents to Induce Human T Regulatory (Treg) Cells: Preferential Treg-Stimulatory Effect of Prednisolone and Rapamycin

T regulatory (Treg) cells play a critical role in the maintenance of self-tolerance, as well as in inhibition of inflammation and exaggerated immune response against exogenous antigens. They develop in the thymus (tTreg cells) but also may be generated at the peripheral tissues, including tumor microenvironment (pTreg cells), or induced in vitro in the presence of transforming growth factor (TGF)-β (iTreg cells). Since tTreg cells constitute a minor fraction of peripheral blood lymphocytes in physiological conditions, an alternative way to obtain high number of functional Treg cells for therapeutic purposes is their generation in vitro from conventional T cells. In our studies, we compared effectiveness of several pharmacological agents with suggested immunomodulatory effects on Treg development (rapamycin, prednisolone, inosine pranobex, glatiramer acetate, sodium butyrate, and atorvastatin) to optimize Treg-inducing protocols. All but one (atorvastatin) immunomodulators augmented induction of polyclonal Treg cells in cultures. They were effective both in increasing the number of CD4⁺CD25^highFoxp3^high cells and Foxp3 expression. Rapamycin and prednisolone were found the most effective. Both drugs prolonged also phenotypic stability of Treg cells and induced fully active Treg cells in a functional assay. In the assay, prednisolone appeared superior versus rapamycin. The results, on the one hand, may be helpful in planning optimal protocols for generation of Treg cells for clinical application and, on the other hand, shed some light on mechanisms of the immunomodulatory activity of some tested agents observed in vivo.

Prospects of the Use of Cell Therapy to Induce Immune Tolerance

Conditions in which abnormal or excessive immune responses exist, such as autoimmune diseases (ADs), graft-versus-host disease, transplant rejection, and hypersensitivity reactions, are serious hazards to human health and well-being. The traditional immunosuppressive drugs used to treat these conditions can lead to decreased immune function, a higher risk of infection, and increased tumor susceptibility. As an alternative therapeutic approach, cell therapy, in which generally intact and living cells are injected, grafted, or implanted into a patient, has the potential to overcome the limitations of traditional drug treatment and to alleviate the symptoms of many refractory diseases. Cell therapy could be a powerful approach to induce immune tolerance and restore immune homeostasis with a deeper understanding of immune tolerance mechanisms and the development of new techniques. The purpose of this review is to describe the current panoramic scope of cell therapy for immune-mediated disorders, discuss the advantages and disadvantages of different types of cell therapy, and explore novel directions and future prospects for these tolerogenic therapies.

Advances on the role of the deleted in breast cancer (DBC1) in cancer and autoimmune diseases

DBC1 (deleted in breast cancer 1) is a human nuclear protein that modulates the activities of various proteins. Most of the research on DBC1 has focused on metabolism and epigenetics because it is a crucial endogenic inhibitor of deacetylase Sirtuin1 (SIRT1). In this review, we have discussed and summarized the new advances in DBC1 research, mostly focusing on its structure, regulatory function, and significance in cancer and autoimmune diseases.

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.

Can we prevent or treat graft-versus-host disease with cellular-therapy?

Acute and chronic graft-versus-host disease (GvHD) are the most important causes of treatment-related morbidity and mortality after allogeneic hematopoietic cell transplants for various diseases. Corticosteroids are an effective therapy in only about one-half of affected individuals and new therapy options are needed. We discuss novel strategies to treat GvHD using cellular-therapy including adoptive transfer of regulatory T-cells (T_regs), mesenchymal stromal cells (MSCs), cells derived from placental tissues, invariant natural killer T-cells (iNKTs), and myeloid-derived suppressor cells (MDSCs).These strategies may be more selective than drugs in modulating GvHD pathophysiology, and may be safer and more effective than conventional pharmacologic therapies. Additionally, these therapies have not been observed to substantially compromise the graft-versus-tumor effect associated with allotransplants. Many of these strategies are effective in animal models but substantial data in humans are lacking.

Rebalancing Immune Homeostasis to Treat Autoimmune Diseases

During homeostasis, interactions between tolerogenic dendritic cells (DCs), self-reactive T cells, and T regulatory cells (Tregs) contribute to maintaining mammalian immune tolerance. In response to infection, immunogenic DCs promote the generation of proinflammatory effector T cell subsets. When complex homeostatic mechanisms maintaining the balance between regulatory and effector functions become impaired, autoimmune diseases can develop. We discuss some of the newest advances on the mechanisms of physiopathologic homeostasis that can be employed to develop strategies to restore a dysregulated immune equilibrium. Some of these designs are based on selectively activating regulators of immunity and inflammation instead of broadly suppressing these processes. Promising approaches include the use of nanoparticles (NPs) to restore Treg control over self-reactive cells, aiming to achieve long-term disease remission, and potentially to prevent autoimmunity in susceptible individuals.

Effects of Xinjiaxiangruyin on the TLR7 pathway in influenza virus-infected lungs of mice housed in a hygrothermal environment

Background

To investigate the effects and immunological mechanisms of the traditional Chinese medicine Xinjiaxiangruyin on controlling influenza virus (FM1 strain) infection in mice housed in a hygrothermal environment.

Methods

Mice were housed in normal and hygrothermal environments, and intranasally infected with influenza virus (FM1). A high-performance liquid chromatography fingerprint of Xinjiaxiangruyin was used to provide an analytical method for quality control. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to measure messenger RNA expression of Toll-like receptor 7 (TLR7), myeloid differentiation primary response 88 (MyD88), and nuclear factor-kappa B (NF-κB) p65 in the TLR7 signaling pathway and virus replication in the lungs. Western blotting was used to measure the expression levels of TLR7, MyD88, and NF-κB p65 proteins. Flow cytometry was used to detect the proportion of Th17/T-regulatory cells.

Results

Xinjiaxiangruyin effectively alleviated lung inflammation in C57BL/6 mice in hot and humid environments. Guizhimahuanggebantang significantly reduced lung inflammation in C57BL/6 mice. The expression of TLR7, MyD88, and NF-κB p65 mRNA in lung tissue of WT mice in the normal environment, GZMHGBT group was significantly lower than that in the model group (P < 0.05). In WT mice exposed to the hot and humid environment, the expression levels of TLR7, MyD88, and NF-κB p65 mRNA in the XJXRY group were significantly different from those in the virus group. The expression levels of TLR7, MyD88, and NF-κB p65 protein in lung tissue of WT mice exposed to the normal environment, GZMHGBT group was significantly lower than those in the model group. In WT mice exposed to hot and humid environments, the expression levels of TLR7, MyD88, and NF-κB p65 protein in XJXRY group were significantly different from those in the virus group.

Conclusion

Guizhimahuanggebantang demonstrated a satisfactory therapeutic effect on mice infected with the influenza A virus (FM1 strain) in a normal environment, and Xinjiaxiangruyin demonstrated a clear therapeutic effect in damp and hot environments and may play a protective role against influenza through downregulation of the TLR7 signal pathway.

Horses with equine recurrent uveitis have an activated CD4+ T-cell phenotype that can be modulated by mesenchymal stem cells in vitro

Equine recurrent uveitis (ERU) is an immune‐mediated disease causing repeated or persistent inflammatory episodes which can lead to blindness. Currently, there is no cure for horses with this disease. Mesenchymal stem cells (MSCs) are effective at reducing immune cell activation in vitro in many species, making them a potential therapeutic option for ERU. The objectives of this study were to define the lymphocyte phenotype of horses with ERU and to determine how MSCs alter T‐cell phenotype in vitro. Whole blood was taken from 7 horses with ERU and 10 healthy horses and peripheral blood mononuclear cells were isolated. The markers CD21, CD3, CD4, and CD8 were used to identify lymphocyte subsets while CD25, CD62L, Foxp3, IFNγ, and IL10 were used to identify T‐cell phenotype. Adipose‐derived MSCs were expanded, irradiated (to control proliferation), and incubated with CD4⁺ T‐cells from healthy horses, after which lymphocytes were collected and analyzed via flow cytometry. The percentages of T‐cells and B‐cells in horses with ERU were similar to normal horses. However, CD4⁺ T‐cells from horses with ERU expressed higher amounts of IFNγ indicating a pro‐inflammatory Th1 phenotype. When co‐incubated with MSCs, activated CD4⁺ T‐cells reduced expression of CD25, CD62L, Foxp3, and IFNγ. MSCs had a lesser ability to decrease activation when cell‐cell contact or prostaglandin signaling was blocked. MSCs continue to show promise as a treatment for ERU as they decreased the CD4⁺ T‐cell activation phenotype through a combination of cell‐cell contact and prostaglandin signaling.

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.

Phenotypic Analysis of CD4+ Treg, CD8+ Treg, and Breg Cells in Adult Common Variable Immunodeficiency Patients

INTRODUCTION

Regulatory lymphocytes (CD4+ T regulatory cells [Treg], CD8+ Treg, and B regulatory cells [Breg]) play a critical role in immune homeostasis and tolerance. Common variable immunodeficiency (CVID) is associated with increased susceptibility to infections and increased frequency of inflammatory and autoimmune diseases. CD4+ Treg cell abnormalities have been reported in CVID; however, CD8+ Treg cells have not been reported in CVID. The objective of this study was to evaluate CD4+ Treg and CD8+ Treg cells in CVID patients.

METHODS

In 25 patients with CVID and age-matched healthy controls, Treg cells, evaluated in freshly isolated peripheral blood mononuclear cells (natural; nCD4+ Treg and nCD8+ Treg) and following in vitro activation with anti-CD3/CD28 monoclonal antibodies (induced; iCD4+ Treg and iCD8+ Treg) as well as Breg cells were analyzed with specific monoclonal antibodies and isotype controls using flow cytometry.

RESULTS

The proportions of nCD4+ Treg (CD4+ CD127low CD25high FoxP3+), iCD4+ Treg (CD4+ CD127low CD25high FoxP3+), iCD8+ Treg (CD8+ CD25high CD183+ FoxP3+), and Breg (CD19+ CD24high CD38high) lymphocytes were significantly lower in patients with CVID than in controls.

CONCLUSIONS

Altered regulatory lymphocytes may play a role in the pathogenesis and autoimmunity and inflammation associated with CVID.

Essential Kinases and Transcriptional Regulators and Their Roles in Autoimmunity

Kinases and transcriptional regulators are fundamental components of cell signaling that are expressed on many types of immune cells which are involved in secretion of cytokines, cell proliferation, differentiation, and apoptosis. Both play important roles in biological responses in health as well as in illnesses such as the autoimmune diseases which comprise at least 80 disorders. These diseases are caused by complex genetic and environmental interactions that lead to a breakage of immunologic tolerance and a disruption of the balance between self-reactive cells and regulatory cells. Kinases or transcriptional regulatory factors often have an abnormal expression in the autoimmune cells that participate in the pathogenesis of autoimmune disease. These abnormally expressed kinases or transcriptional regulators can over-activate the function of self-reactive cells to produce inflammatory cytokines or down-regulate the activity of regulatory cells, thus causing autoimmune diseases. In this review we introduce five kinds of kinase and transcriptional regulator related to autoimmune diseases, namely, members of the Janus kinase (JAK) family (JAK3 and/or tyrosine kinase 2 (TYK2)), fork head box protein 3 (Foxp3), the retinoic acid-related orphan receptor gamma t (RORγt), and T-box expressed in T cells (T-bet) factors. We also provide a mechanistic insight into how these kinases and transcriptional regulators affect the function of the immune cells related to autoimmune diseases, as well as a description of a current drug design targeting these kinases and transcriptional regulators. Understanding their exact role helps offer new therapies for control of the inflammatory responses that could lead to clinical improvement of the autoimmune diseases.

1,25-Dihydroxyvitamin D3 Ameliorates Collagen-Induced Arthritis via Suppression of Th17 Cells Through miR-124 Mediated Inhibition of IL-6 Signaling

Objectives: To explore the molecular mechanisms in which vitamin D (VD) regulates T cells, especially Th17 cells in collagen-induced arthritis (CIA). Methods: DBA1/J mice induced for CIA were intraperitoneally treated with VD. CIA clinical symptoms and inflammatory responses including Th1/Th17/Tregs percentages were determined and compared. Mouse naïve CD4⁺ T cells transduced with miR-124 inhibitor or not were polarized to Th17 cells with or without VD. Subsequently, cellular differentiation and IL-6 signaling moleculars were analyzed. Results: VD treatment significantly delayed CIA onset, decreased incidence and clinical scores of arthritis, downregulated serum IgG levels and ameliorated bone erosion. VD downregulated IL-17A production in CD4⁺ T cells while increased CD4⁺Foxp3⁺Nrp-1⁺ cells both in draining lymph nodes and synovial fluid in arthritic mice. VD inhibited Th17 cells differentiation in vivo and in vitro and potentially functioning directly on T cells to restrain Th17 cells through limiting IL-6R expression and its downstream signaling including STAT3 phosphorylation, while these effects were blocked when naïve CD4⁺ T cells were transduced with miR-124 inhibitor. Conclusions: VD treatment ameliorates CIA via suppression of Th17 cells and enhancement of Tregs. miR-124-mediated inhibition of IL-6 signaling, provides a novel explanation for VD's role on T cells in CIA mice or RA patients and suggests that VD may have treatment implications in rheumatoid arthritis.

Immunoregulatory role of acid sphingomyelinase in allergic asthma

Acid sphingomyelinase (ASM) is one of the enzymes that catalyzes the breakdown of sphingomyelin to ceramide and phosphorylcholine. In this study, we aimed at elucidating the role of ASM in allergic asthma. We used an ovalbumin-induced murine model of asthma where we compared wild-type and ASM-deficient mice. In wild-type mice, secretory ASM activity in the bronchoalveolar lavage fluid was increased in the acute ovalbumin model, but not in a tolerogenic model. Furthermore, in the absence of ASM, the serum IgE level was reduced, compared with wild-type mice, while an accumulation of interstitial macrophages and foreign antigen-induced regulatory T cells along with exhausted CD4⁺ PD1⁺ T cells was observed in the lungs of ASM^-/- mice. In conclusion, in the absence of ASM, we observed an accumulation of immunosuppressive antigen-induced regulatory T cells expressing Foxp3 and CTLA4 in the lung as well as multinucleated interstitial macrophages and exhausted CD4⁺ PD1⁺ T cells associated with inhibition of serum IgE in asthma.

Notch and NF-κB: Coach and Players of Regulatory T-Cell Response in Cancer

The Notch signaling pathway plays multiple roles in driving T-cell fate decisions, proliferation, and aberrant growth. NF-κB is a cell-context key player interconnected with Notch signaling either in physiological or in pathological conditions. This review focuses on how the multilayered crosstalk between different Notches and NF-κB subunits may converge on Foxp3 gene regulation and orchestrate CD4⁺ regulatory T (Treg) cell function, particularly in a tumor microenvironment. Notably, Treg cells may play a pivotal role in the inhibition of antitumor immune responses, possibly promoting tumor growth. A future challenge is represented by further dissection of both Notch and NF-κB pathways and consequences of their intersection in tumor-associated Treg biology. This may shed light on the molecular mechanisms regulating Treg cell expansion and migration to peripheral lymphoid organs thought to facilitate tumor development and still to be explored. In so doing, new opportunities for combined and/or more selective therapeutic approaches to improve anticancer immunity may be found.