Increased numbers of CD5+CD19+CD1dhighIL-10+ Bregs, CD4+Foxp3+ Tregs, CD4+CXCR5+Foxp3+ follicular regulatory T (TFR) cells in CHB or CHC patients

Methylprednisolone Modulates the Tfr/Tfh ratio in EAE-Induced Neuroinflammation through the PI3K/AKT/FoxO1 and PI3K/AKT/mTOR Signalling Pathways

Methylprednisolone (MP) is a potent glucocorticoid that can effectively inhibit immune system inflammation and brain tissue damage in Multiple sclerosis (MS) patients. T follicular helper (Tfh) cells are a subpopulation of activated CD4 + T cells, while T follicular regulatory (Tfr) cells, a novel subset of Treg cells, possess specialized abilities to suppress the Tfh-GC response and inhibit antibody production. Dysregulation of either Tfh or Tfr cells has been implicated in the pathogenesis of MS. However, the molecular mechanism underlying the anti-inflammatory effects of MP therapy on experimental autoimmune encephalomyelitis (EAE), a representative model for MS, remains unclear. This study aimed to investigate the effects of MP treatment on EAE and elucidate the possible underlying molecular mechanisms involed. We evaluated the effects of MP on disease progression, CNS inflammatory cell infiltration and myelination, microglia and astrocyte activation, as well as Tfr/Tfh ratio and related molecules/inflammatory factors in EAE mice. Additionally, Western blotting was used to assess the expression of proteins associated with the PI3K/AKT pathway. Our findings demonstrated that MP treatment ameliorated clinical symptoms, inflammatory cell infiltration, and myelination. Furthermore, it reduced microglial and astrocytic activation. MP may increase the number of Tfr cells and the levels of cytokine TGF-β1, while reducing the number of Tfh cells and the levels of cytokine IL-21, as well as regulate the imbalanced Tfr/Tfh ratio in EAE mice. The PI3K/AKT/FoxO1 and PI3K/AKT/mTOR pathways were found to be involved in EAE development. However, MP treatment inhibited their activation. MP reduced neuroinflammation in EAE by regulating the balance between Tfr/Tfh cells via inhibition of the PI3K/AKT/FoxO1 and PI3K/AKT/mTOR signalling pathways.

Stability and plasticity of regulatory T cells in health and disease

The mechanisms that negatively regulate inflammation upon a pathogenic stimulus are crucial for the maintenance of tissue integrity and organ function. T regulatory cells are one of the main drivers in controlling inflammation. The ability of T regulatory cells to adapt to different inflammatory cues and suppress inflammation is one of the relevant features of T regulatory cells. During this process, T regulatory cells express different transcription factors associated with their counterparts, Th helper cells, including Tbx21, GATA-3, Bcl6, and Rorc. The acquisition of this transcription factor helps the T regulatory cells to suppress and migrate to the different inflamed tissues. Additionally, the T regulatory cells have different mechanisms that preserve stability while acquiring a particular T regulatory cell subtype. This review focuses on describing T regulatory cell subtypes and the mechanisms that maintain their identity in health and diseases.

The Multiple Facets and Disorders of B Cell Functions in Hepatitis B Virus Infection

Chronic hepatitis B virus (HBV) infection continues to be a global public health burden. B cells play a pivotal role in mediating HBV clearance and can participate in the development of anti-HBV adaptive immune responses through multiple mechanisms, such as antibody production, antigen presentation, and immune regulation. However, B cell phenotypic and functional disorders are frequently observed during chronic HBV infection, suggesting the necessity of targeting the disordered anti-HBV B cell responses to design and test new immune therapeutic strategies for the treatment of chronic HBV infection. In this review, we provide a comprehensive summary of the multiple roles of B cells in mediating HBV clearance and pathogenesis as well as the latest developments in understanding the immune dysfunction of B cells in chronic HBV infection. Additionally, we discuss novel immune therapeutic strategies that aim to enhance anti-HBV B cell responses for curing chronic HBV infection.

Standard immunosuppressive treatment reduces regulatory B cells in children with autoimmune liver disease

Introduction

Autoimmune hepatitis (AIH) is a chronic liver disease caused by a perturbed immune system. The scarcity of short- and long-term immune monitoring of AIH hampered us to comprehend the interaction between immunosuppressive medication and immune homeostasis.

Methods and patients

We recruited children with AIH at the time of diagnosis and at the 1st, 3rd, 6th, 12th, 18th, and 24th months of immunosuppression (IS). We also enrolled children with AIH being on IS for >2 years. Children with drug-induced liver injury (DILI), and those receiving tacrolimus after liver transplantation (LT), were enrolled as disease/IS control subjects. Healthy children (HC) were also recruited. Peripheral blood mononuclear cells (PBMCs) were isolated from all participants. Healthy liver tissue from adult donors and from livers without inflammation were obtained from children with hepatoblastoma. By using flow cytometry, we performed multi-parametric immune profiling of PBMCs and intrahepatic lymphocytes. Additionally, after IS with prednisolone, tacrolimus, rapamycin, or 6-mercaptopurine, we carried out an in vitro cytokine stimulation assay. Finally, a Lifecodes SSO typing kit was used to type HLA-DRB1 and Luminex was used to analyze the results.

Results

Untreated AIH patients had lower total CD8 T-cell frequencies than HC, but these cells were more naïve. While the percentage of naïve regulatory T cells (Tregs) (CD4⁺FOXP3^lowCD45RA⁺) and regulatory B cells (Bregs, CD20⁺CD24⁺CD38⁺) was similar, AIH patients had fewer activated Tregs (CD4⁺FOXP3^highCD45RA ^- ) compared to HC. Mucosal-associated-invariant-T-cells (MAIT) were also lower in these patients. Following the initiation of IS, the immune profiles demonstrated fluctuations. Bregs frequency decreased substantially at 1 month and did not recover anymore. Additionally, the frequency of intrahepatic Bregs in treated AIH patients was lower, compared to control livers, DILI, and LT patients. Following in vitro IS drugs incubation, only the frequency of IL-10-producing total B-cells increased with tacrolimus and 6MP. Lastly, 70% of AIH patients possessed HLA-DR11, whereas HLA-DR03/DR07/DR13 was present in only some patients.

Conclusion

HLA-DR11 was prominent in our AIH cohort. Activated Tregs and MAIT cell frequencies were lower before IS. Importantly, we discovered a previously unrecognized and long-lasting Bregs scarcity in AIH patients after IS. Tacrolimus and 6MP increased IL-10+ B-cells in vitro.

Hepatocytes infected with hepatitis C virus change immunological features in the liver microenvironment

Hepatitis C virus (HCV) infection is remarkably efficient in establishing viral persistence, leading to the development of liver cirrhosis and hepatocellular carcinoma (HCC). Direct-acting antiviral agents (DAAs) are promising HCV therapies to clear the virus. However, recent reports indicate potential increased risk of HCC development among HCV patients with cirrhosis following DAA therapy. CD8+ T-cells participate in controlling HCV infection. However, in chronic hepatitis C patients, severe CD4+ and CD8+ T-cell dysfunctions have been observed. This suggests that HCV may employ mechanisms to counteract or suppress the host T-cell responses. The primary site of viral replication is within hepatocytes where infection can trigger the expression of costimulatory molecules and the secretion of immunoregulatory cytokines. Numerous studies indicate that HCV infection in hepatocytes impairs antiviral host immunity by modulating the expression of immunoregulatory molecules. Hepatocytes expressing whole HCV proteins upregulate the ligands of programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), and transforming growth factor β (TGF-β) synthesis compared to those in hepatocytes in the absence of the HCV genome. Importantly, HCV-infected hepatocytes are capable of inducing regulatory CD4+ T-cells, releasing exosomes displaying TGF-β on exosome surfaces, and generating follicular regulatory T-cells. Recent studies report that the expression profile of exosome microRNAs provides biomarkers of HCV infection and HCV-related chronic liver diseases. A better understanding of the immunoregulatory mechanisms and identification of biomarkers associated with HCV infection will provide insight into designing vaccine against HCV to bypass HCV-induced immune dysregulation and prevent development of HCV-associated chronic liver diseases.

Exosome-mediated effects and applications in inflammatory diseases of the digestive system

Exosomes are membranous vesicles containing RNA and proteins that are specifically secreted in vivo. Exosomes have many functions, such as material transport and signal transduction between cells. Many studies have proven that exosomes can not only be used as biomarkers for disease diagnosis but also as carriers to transmit information between cells. Exosomes participate in a variety of physiological and pathological processes, including the immune response, antigen presentation, cell migration, cell differentiation, and tumour development. Differences in exosome functions depend on cell type. In recent years, exosome origin, cargo composition, and precise regulatory mechanisms have been the focus of research. Although exosomes have been extensively reported in digestive tumours, few articles have reviewed their roles in inflammatory diseases of the digestive system, especially inflammatory-related diseases (such as reflux oesophagitis, gastritis, inflammatory bowel disease, hepatitis, and pancreatitis). This paper briefly summarizes the roles of exosomes in inflammatory diseases of the digestive system to provide a basis for research on the mechanism of inflammatory diseases of the digestive system targeted by exosomes.

Changes in circulating TCF1- and GARP-associated regulatory T cell subsets reflect the clinical status of patients with chronic HBV infection

This study aimed to clarify the expression changes and clinical significance of regulatory T (Treg) cells and follicular regulatory T (TFR) cell subsets divided by glycoprotein A repetitions predominant protein (GARP) and T cell factor 1(TCF1) in peripheral blood of patients with chronic HBV infection. The peripheral blood of 26 chronic hepatitis B (CHB) patients, 27 inactive HBsAg carriers and 32 healthy controls were collected and GARP + percentages in Treg and TFR cells were analyzed by flow cytometry. In addition, Treg and TFR cell subsets sorted by CD62L and TCF1 were analyzed and compared. Correlation analyses were performed between Treg and TFR cell subpopulations and clinical parameters as well as cytokine concentrations, including IL-21, IL-10 and TGF-β1 in plasma. Circulating Treg and TFR levels were elevated in CHB patients. Moreover, GARP and TCF1 were up-regulated in circulating Treg and TFR cells of CHB patients. TCF1 + CD62L- Treg cells were increased while TCF1-CD62L + Treg cells were decreased in CHB patients. TCF1 + CD62L- and TCF1-CD62L- TFR cells were increased while TCF1 + CD62L + TFR cells were decreased in CHB patients. TCF1 + CD62L- Treg cells were positively correlated with HBV DNA, ALT and plasma IL-10, while TCF1 + CD62L + TFR cells were negatively correlated with HBV DNA, HBeAg, HBsAg, ALT, AST, T-BIL and positively correlated with plasma IL-21. Treg and TFR subsets sorted by TCF1, CD62L and GARP were changed in CHB patients. Changes in Treg and TFR functional subsets are associated with antiviral immunity in CHB patients.

The interaction between the soluble programmed death ligand-1 (sPD-L1) and PD-1+ regulator B cells mediates immunosuppression in triple-negative breast cancer

Accumulating evidence suggests that regulatory B cells (Bregs) play important roles in inhibiting the immune response in tumors. Programmed death 1 (PD-1) and programmed death ligand 1 (PD-L1) are important molecules that maintain the balance of the immune response and immune tolerance. This study aims to evaluate the soluble form of PD-L1 and its function in inducing the differentiation of B lymphocytes, investigate the relationship between soluble PD-L1 (sPD-L1) and B-cell subsets, and explore the antitumor activity of T lymphocytes after PD-L1 blockade in coculture systems. In an effort to explore the role of sPD-L1 in human breast cancer etiology, we examined the levels of sPD-L1 and interleukin-10 (IL-10) in the serum of breast tumor patients and the proportions of B cells, PD-1⁺ B cells, Bregs, and PD-1⁺ Bregs in the peripheral blood of patients with breast tumors and assessed their relationship among sPD-L1, IL-10, and B-cell subsets. The levels of sPD-L1 and IL-10 in serum were found to be significantly higher in invasive breast cancer (IBCa) patients than in breast fibroadenoma (FIBma) patients. Meanwhile, the proportions and absolute numbers of Bregs and PD-1⁺ Bregs in the peripheral blood of IBCa patients were significantly higher than those of FIBma patients. Notably, they were the highest in triple-negative breast cancer (TNBC) among other subtypes of IBCa. Positive correlations of sPD-L1 and IL-10, IL-10 and PD-1⁺ Bregs, and also sPD-L1 and PD-1⁺ Bregs were observed in IBCa. We further demonstrated that sPD-L1 could induce Breg differentiation, IL-10 secretion, and IL-10 mRNA expression in a dose-dependent manner in vitro. Finally, the induction of regulatory T cells (T_regs) by Bregs was further shown to suppress the antitumor response and that PD-L1 blockade therapies could promote the apoptosis of tumor cells. Together, these results indicated that sPD-L1 could mediate the differentiation of Bregs, expand CD4⁺ T_regs and weaken the antitumor activity of CD4⁺ T cells. PD-L1/PD-1 blockade therapies might be a powerful therapeutic strategy for IBCa patients, particularly for TNBC patients with high level of PD-1⁺ Bregs.

Hepatitis B Flare in Hepatitis B e Antigen-Negative Patients: A Complicated Cascade of Innate and Adaptive Immune Responses

Chronic hepatitis B virus (HBV) infection is a dynamic process involving interactions among HBV, hepatocytes, and the host immune system. The natural course of chronic hepatitis B (CHB) is divided into four chronological phases, including the hepatitis B e antigen (HBeAg)-positive and HBeAg-negative phases. During HBV flare, alanine aminotransferase (ALT) levels abruptly rise to >5× the upper limit of normal; this is thought to occur due to the immune response against an upsurge in serum HBV DNA and antigen levels. Hepatitis flares may occur spontaneously, during or after antiviral therapy, or upon immunosuppression or chemotherapy in both HBeAg-positive and HBeAg-negative patients. The clinical spectrum of HBV flares varies from asymptomatic to hepatic decompensation or failure. HBeAg seroconversion with ≥ 1 year of consolidation therapy is accepted as an endpoint of oral antiviral therapy in HBeAg-positive patients, but recommendations for treating HBeAg-negative patients differ. Thus, the management of HBeAg-negative patients has attracted increasing interest. In the current review, we summarize various types of HBV flares and the associated complex cascade of innate and adaptive immune responses, with a focus on HBeAg-negative CHB patients. Hopefully, this review will provide insight into immunopathogenesis to improve the management of HBV flares in HBeAg-negative CHB patients.

Cytokines and Chemokines in HBV Infection

Chronic hepatitis B virus (HBV) infection remains a leading cause of hepatic inflammation and damage. The pathogenesis of chronic hepatitis B (CHB) infection is predominantly mediated by persistent intrahepatic immunopathology. With the characterization of unique anatomical and immunological structure, the liver is also deemed an immunological organ, which gives rise to massive cytokines and chemokines under pathogenesis conditions, having significant implications for the progression of HBV infection. The intrahepatic innate immune system is responsible for the formidable source of cytokines and chemokines, with the latter also derived from hepatic parenchymal cells. In addition, systemic cytokines and chemokines are disturbed along with the disease course. Since HBV is a stealth virus, persistent exposure to HBV-related antigens confers to immune exhaustion, whereby regulatory cells are recruited by intrahepatic chemokines and cytokines, including interleukin-10 and transforming growth factor β, are involved in such series of causal events. Although the considerable value of two types of available approved treatment, interferons and nucleos(t)ide analogues, effectively suppress HBV replication, neither of them is sufficient for optimal restoration of the immunological attrition state to win the battle of the functional or virological cure of CHB infection. Notably, cytokines and chemokines play a crucial role in regulating the immune response. They exert effects by directly acting on HBV or indirectly manipulating target immune cells. As such, specific cytokines and chemokines, with a potential possibility to serve as novel immunological interventions, combined with those that target the virus itself, seem to be promising prospects in curative CHB infection. Here, we systematically review the recent literature that elucidates cytokine and chemokine-mediated pathogenesis and immune exhaustion of HBV infection and their dynamics triggered by current mainstream anti-HBV therapy. The predictive value of disease progression or control and the immunotherapies target of specific major cytokines and chemokines in CHB infection will also be delineated.

B Cell-mediated Humoral Immunity in Chronic Hepatitis B Infection

B cell-mediated humoral immunity plays a vital role in viral infections, including chronic hepatitis B virus (HBV) infection, which remains a critical global public health issue. Despite hepatitis B surface antigen-specific antibodies are essential to eliminate viral infections, the reduced immune functional capacity of B cells was identified, which was also correlated with chronic hepatitis B (CHB) progression. In addition to B cells, T follicular helper (Tfh) cells, which assist B cells to produce antibodies, might also be involved in the process of anti-HBV-specific antibody production. Here, we provide a comprehensive review of the role of various subsets of B cells and Tfh cells during CHB progression and discuss current novel treatment strategies aimed at restoring humoral immunity. Understanding the mechanism of dysregulated B cells and Tfh cells will facilitate the ultimate functional cure of CHB patients.

Immunopathology of Chronic Hepatitis B Infection: Role of Innate and Adaptive Immune Response in Disease Progression

More than 250 million people are living with chronic hepatitis B despite the availability of highly effective vaccines and oral antivirals. Although innate and adaptive immune cells play crucial roles in controlling hepatitis B virus (HBV) infection, they are also accountable for inflammation and subsequently cause liver pathologies. During the initial phase of HBV infection, innate immunity is triggered leading to antiviral cytokines production, followed by activation and intrahepatic recruitment of the adaptive immune system resulting in successful virus elimination. In chronic HBV infection, significant alterations in both innate and adaptive immunity including expansion of regulatory cells, overexpression of co-inhibitory receptors, presence of abundant inflammatory mediators, and modifications in immune cell derived exosome release and function occurs, which overpower antiviral response leading to persistent viral infection and subsequent immune pathologies associated with disease progression towards fibrosis, cirrhosis, and hepatocellular carcinoma. In this review, we discuss the current knowledge of innate and adaptive immune cells transformations that are associated with immunopathogenesis and disease outcome in CHB patients.

Potential Application of T-Follicular Regulatory Cell Therapy in Transplantation

Regulatory T cells (Tregs) constitute a small proportion of circulating CD4⁺ T cells that function to maintain homeostasis and prevent autoimmunity. In light of their powerful immunosuppressive and tolerance-promoting properties, Tregs have become an interesting potential candidate for therapeutic use in conditions such as solid organ transplant or to treat autoimmune and inflammatory conditions. Clinical studies have demonstrated the safety of polyclonally expanded Tregs in graft-versus-host disease, type 1 diabetes, and more recently in renal and liver transplantation. However, Tregs are heterogenous. Recent insights indicate that only a small proportion of Tregs, called T follicular regulatory cells (Tfr) regulate interactions between B cells and T follicular helper (Tfh) cells within the germinal center. Tfr have been mainly described in mouse models due to the challenges of sampling secondary lymphoid organs in humans. However, emerging human studies, characterize Tfr as being CD4⁺CD25⁺FOXP3⁺CXCR5⁺ cells with different levels of PD-1 and ICOS expression depending on their localization, in the blood or the germinal center. The exact role they play in transplantation remains to be elucidated. However, given the potential ability of these cells to modulate antibody responses to allo-antigens, there is great interest in exploring translational applications in situations where B cell responses need to be regulated. Here, we review the current knowledge of Tfr and the role they play focusing on human diseases and transplantation. We also discuss the potential future applications of Tfr therapy in transplantation and examine the evidence for a role of Tfr in antibody production, acute and chronic rejection and tertiary lymphoid organs. Furthermore, the potential impact of immunosuppression on Tfr will be explored. Based on preclinical research, we will analyse the rationale of Tfr therapy in solid organ transplantation and summarize the different challenges to be overcome before Tfr therapy can be implemented into clinical practice.

The Multiple Functions of B Cells in Chronic HBV Infection

Chronic hepatitis B virus (HBV) infection is one of the main causes of liver diseases, of which the natural history and clinical outcomes are associated with the role of B cells. As humoral immune cells, B cells play a critical role in the process of anti-HBV antibody production. In addition, some studies have also characterized other B cell subsets involved in antigen presentation and regulating the immune response beyond antibody secretion. However, not all B cell subsets play a positive role in the immune response to chronic HBV infection, and various B cell subsets jointly mediate persistent HBV infection, tolerance, and liver damage. Thus, we further sought to elucidate the multiple functions of B cells to gain novel insight into the understanding of chronic hepatitis B (CHB) pathogenesis. We also reviewed the current immunotherapies targeting B cells to explore novel therapeutic interventions for the treatment of chronic HBV infection.

Impact of deranged B cell subsets distribution in the development of HCV-related cirrhosis and HCC in type two diabetes mellitus

Type II diabetes (T2D) may worsen the course of hepatitis C virus infection with a greater risk of liver cirrhosis (LC) and hepatocellular carcinoma (HCC). In chronic viral infections, the deranged B cell subset signifies uncontrolled disease. The study aimed to verify the relation between B cell subsets' distribution and liver disease progression in chronic hepatitis C (CHC) patients with T2D. A total of 67 CHC patients were divided into two groups; 33 non-diabetic and 34 with T2D. Each group was subdivided into CHC-without LC or HCC (N-CHC), CHC-with LC (CHC-LC), and CHC-with HCC (CHC-HCC). Twenty-seven healthy individuals also participated as controls. Flow cytometry was used to analyze CD19+ B cell subsets based on the expression of CD24 and CD38. CD19+CD24hiCD38hi Immature/transitional B cells elevated in diabetic than non-diabetic patients. In diabetic patients, while CD19+CD24+CD38- primarily memory B cells were higher in CHC-N and CHC-HCC groups than LC with a good predictive accuracy of LC, the opposite was observed for CD19+CD24-CD38- new memory B cells. Only in diabetic patients, the CD19+CD24intCD38int naïve mature B cells were high in CHC-HCC patients with good prognostic accuracy of HCC. Merely in diabetic patients, several correlations were observed between B cell subsets and liver function. Immature/transitional B cells increase remarkably in diabetic CHCpatients and might have a role in liver disease progression. Memory and Naïve B cells are good potential predictors of LC and HCCin diabetic CHCpatients, respectively. Further studies are needed to investigate the role of the CD19+CD24-CD38- new memory B cells in disease progression in CHC patients.

Tfr-Tfh index: A new predicator for recurrence of hepatocellular carcinoma patients with HBV infection after curative resection

BACKGROUND

T follicular helper (Tfh) cells and T follicular regulatory (Tfr) cells were newly identified as the subsets of cluster of CD4+ T cells. As major components of human immune system, they were found in tumor microenvironment and reported to play vital roles in the progression of cancer. But their clinical significance in Hepatocellular carcinoma (HCC) was not elucidated. Thus, this research aimed to investigate their prognostic value in HCC.

MATERIALS AND METHODS

A total of 210 subjects (including 110 HCC patients, 50 chronic hepatitis patients and 50 healthy individuals) were enrolled in the research. Tfh, Tfr cells and Treg cells from peripheral blood were measured by flow cytometry. Receiver operating characteristic (ROC) curves were used to evaluate the diagnostic performance of Tfr-Tfh Index (TTI) in early HCC and relapse status. Its further prognostic valve was assessed by Kaplan-Meier survival estimate and log rank tests.

RESULTS

Tfh cells, Tfr cells, Treg cells and TTI were all higher in HCC patients than in chronic hepatitis patients and healthy control. TTI was found to have positive correlation with the load of HBV. The AUC of TTI for early HCC and relapse status was better than other clinical indices in HBV positive patients. An optimal cutoff point for the TTI stratified the HCC patients into high (>21.96) and low index (≤21.96) groups. High TTI was significantly correlated with recurrence. Univariate and multivariate analyses revealed TTI could be a predictor for recurrence. Moreover, it retained prognostic performance for patients with lower recurrence risk.

CONCLUSION

Our research showed that TTI could be a promising indicator for early recurrence in HCC patients with HBV infection.

Lymphocyte Landscape after Chronic Hepatitis C Virus (HCV) Cure: The New Normal

Chronic HCV (CHC) infection is the only chronic viral infection for which curative treatments have been discovered. These direct acting antiviral (DAA) agents target specific steps in the viral replication cycle with remarkable efficacy and result in sustained virologic response (SVR) or cure in high (>95%) proportions of patients. These treatments became available 6–7 years ago and it is estimated that their real impact on HCV related morbidity, including outcomes such as cirrhosis and hepatocellular carcinoma (HCC), will not be known for the next decade or so. The immune system of a chronically infected patient is severely dysregulated and questions remain regarding the immune system’s capacity in limiting liver pathology in a cured individual. Another important consequence of impaired immunity in patients cleared of HCV with DAA will be the inability to generate protective immunity against possible re-infection, necessitating retreatments or developing a prophylactic vaccine. Thus, the impact of viral clearance on restoring immune homeostasis is being investigated by many groups. Among the important questions that need to be answered are how much the immune system normalizes with cure, how long after viral clearance this recalibration occurs, what are the consequences of persisting immune defects for protection from re-infection in vulnerable populations, and does viral clearance reduce liver pathology and the risk of developing hepatocellular carcinoma in individuals cured with these agents. Here, we review the recent literature that describes the defects present in various lymphocyte populations in a CHC patient and their status after viral clearance using DAA treatments.

T Cells in Fibrosis and Fibrotic Diseases

Fibrosis is the extensive deposition of fibrous connective tissue, and it is characterized by the accumulation of collagen and other extracellular matrix (ECM) components. Fibrosis is essential for wound healing and tissue repair in response to a variety of triggers, which include infection, inflammation, autoimmune disorder, degenerative disease, tumor, and injury. Fibrotic remodeling in various diseases, such as liver cirrhosis, pulmonary fibrosis, renal interstitial fibrosis, myocardial infarction, systemic sclerosis (SSc), and graft-versus-host disease (GVHD), can impair organ function, causing high morbidity and mortality. Both innate and adaptive immunity are involved in fibrogenesis. Although the roles of macrophages in fibrogenesis have been studied for many years, the underlying mechanisms concerning the manner in which T cells regulate fibrosis are not completely understood. The T cell receptor (TCR) engages the antigen and shapes the repertoire of antigen-specific T cells. Based on the divergent expression of surface molecules and cell functions, T cells are subdivided into natural killer T (NKT) cells, γδ T cells, CD8⁺ cytotoxic T lymphocytes (CTL), regulatory T (Treg) cells, T follicular regulatory (Tfr) cells, and T helper cells, including Th1, Th2, Th9, Th17, Th22, and T follicular helper (Tfh) cells. In this review, we summarize the pro-fibrotic or anti-fibrotic roles and distinct mechanisms of different T cell subsets. On reviewing the literature, we conclude that the T cell regulations are commonly disease-specific and tissue-specific. Finally, we provide perspectives on microbiota, viral infection, and metabolism, and discuss the current advancements of technologies for identifying novel targets and developing immunotherapies for intervention in fibrosis and fibrotic diseases.

Control of foreign Ag-specific Ab responses by Treg and Tfr

Regulatory T cells (Tregs) expressing the transcription factor Foxp3 play a critical role in the control of immune homeostasis including the regulation of humoral immunity. Recently, it has become clear that a specialized subset of Tregs, T-follicular regulatory cells (Tfr), have a particular role in the control of T-follicular helper (Tfh) cell-driven germinal center (GC) responses. Following similar differentiation signals as received by Tfh, Tfr gain expression of characteristic chemokine receptors and transcription factors such as CXCR5 and BCL6 allowing them to travel to the B-cell follicle and deliver in situ suppression. It seems clear that Tfr are critical for the prevention of autoimmune antibody induction. However, their role in the control of foreign antigen-specific antibody responses appears more complex with various reports demonstrating either increased or decreased antigen-specific antibody responses following inhibition of Tfr function. Due to their recent discovery, our understanding of Tfr formation and function still has many gaps. In this review, we discuss our current knowledge of both Tregs and Tfr in the context of humoral immunity and how these cells might be manipulated in order to better control vaccine responses.

Neutralization of IL-10 produced by B cells promotes protective immunity during persistent HCV infection in humanized mice

Chronic HCV infection can lead to cirrhosis and is associated with increased mortality. Interleukin (IL)-10-producing B cells (B10 cells) are regulatory cells that suppress cellular immune responses. Here, we aimed to determine whether HCV induces B10 cells and assess the roles of the B10 cells during HCV infection. HCV-induced B10 cells were enriched in CD19^hi and CD1d^hi CD5⁺ cell populations. HCV predominantly triggered the TLR2-MyD88-NF-κB and AP-1 signaling pathways to drive IL-10 production by B cells. In a humanized murine model of persistent HCV infection, to neutralize IL-10 produced by B10 cells, mice were treated with pcCD19scFv-IL-10R, which contains the genes coding the anti-CD19 single-chain variable fragment (CD19scFv) and the extracellular domain of IL-10 receptor alpha chain (sIL-10Ra). This treatment resulted in significant reduction of B10 cells in spleen and liver, increase of cytotoxic CD8⁺ T-cell responses against HCV, and low viral loads in infected humanized mice. Our results indicate that targeting B10 cells via neutralization of IL-10 may offer a novel strategy to enhance anti-HCV immunotherapy.

Altered ratio of circulating follicular regulatory T cells and follicular helper T cells during primary EBV infection

Follicular help T cells (Tfh) play an important role in the activation and differentiation of B cells, while follicular regulatory T cells (Tfr) control Tfh and resulting humoral immune responses. Accumulating evidence has demonstrated that the dysregulation of Tfr contributed to the pathogenesis of infectious diseases. However, the role of Tfr in Epstein-Barr virus (EBV) infection remains lacking. Fifty-five EBV-infected infectious mononucleosis (IM) patients and 21 healthy individuals (HIs) were recruited in the study. We investigated the number of Tfr (FoxP3⁺CXCR5⁺PD-1⁺CD4⁺) and Tfh (FoxP3^-CXCR5⁺PD-1⁺CD4⁺) of peripheral blood in IM patients at diagnosis (D0) and day 15 after diagnosis (D15) via multicolor flow cytometry. Results revealed that circulating Tfh (cTfh) and Tfr (cTfr) of IM at D0 were both increased compared to HIs, and cTfr began to decline and return to normal at D15, while cTfh was still higher than those of HIs. More interestingly, the cTfr/cTfh ratio of IM at D0 and D15 was lower than that of HIs, suggesting that the balance between cTfh and cTfr was disturbed during primary EBV infection. Correlation analysis showed a positive correlation between cTfr with CD19⁺IgD⁺CD27^- naive B cells, CD19⁺IgD^-CD27^hi plasmablasts or CD19⁺CD24^hiCD27^hi B cells. Moreover, both cTfr and the cTfr/cTfh ratio of IM at D0 were negatively correlated with EBV DNA virus load. These results indicate that an imbalance of cTfr and cTfh cells may be involved in the immunopathogenesis of EBV-infected IM patients and may provide novel strategies for controlling EBV-related disease.

CD19+CD24hiCD38hi regulatory B cells: a potential immune predictive marker of severity and therapeutic responsiveness of hepatitis C

OBJECTIVES

Hepatitis C virus (HCV) infection is associated with abnormal immune responses. Since regulatory T (Tregs) and B (Bregs) cells modulate the progression of infectious diseases, this study aimed at examining how these cells are involved with the development of HCV infection.

METHODS

The frequencies of circulating Bregs and Tregs were characterized using flow cytometry. Both the association and dynamic changes of these cells with related clinical parameters were analyzed after Direct-Acting Antiviral (DAA) agent treatments. Additionally, both regulatory B and T and naïve B and T cells were sorted and stimulated with healthy or HCV sera in vitro.

RESULTS

Bregs frequency in HCV-infected patients increased significantly and were positively correlated with levels of sera HCV RNA load, Alanine aminotransferase (AST) and total bilirubin (TBILI). Additionally, the increased Bregs returned to normal levels after DAA treatment. However, Tregs increased markedly in patients with HCV-cirrhosis and were significantly associated with Aspartate aminotransferase to Platelet Ratio Index (APRI) and Fibrosis 4 (FIB-4) scores. Furthermore, HCV sera doesn't expand either Tregs or Bregs, however, it does induce the IL-10 expression in B cells although it fails to induce FOXP3 expression in CD4+ T cells.

CONCLUSIONS

Increased Bregs not only may be associated with poor viral eradication and liver injury but also may provide a predictive marker of HCV disease therapeutic efficacy following DAA-treatment. HCV sera may selectively induce Bregs. Tregs probably do not control disease status in the early stages but may contribute to the progression of liver fibrosis in the late stages of HCV infection.

Follicular regulatory T cells: a novel target for immunotherapy?

High‐affinity antibodies are produced during multiple processes in germinal centres (GCs), where follicular helper T (Tfh) cells interact closely with B cells to support B‐cell survival, differentiation and proliferation. Recent studies have revealed that a specialised subset of regulatory T cells, follicular regulatory T (Tfr) cells, especially fine‐tune Tfh cells and GC B cells, ultimately regulating GC reactions. Alterations in frequencies or function of Tfr cells may result in multiple autoantibody‐mediated or autoantibody‐associated diseases. This review discusses recent insights into the physiology and pathology of Tfr cells, with a special emphasis on their potential roles in human diseases. Discrepancies are common among studies, reflecting the limited understanding of Tfr cells. Further exploration of the mechanisms of Tfr cells in these diseases and thus targeting Tfr cells may help reinstate immune homeostasis and provide novel immunotherapy.

Phenotypic identification of CD19+CD5+CD1d+ regulatory B cells that produce interleukin 10 and transforming growth factor β1 in human peripheral blood

INTRODUCTION

Regulatory B cells (Bregs), a novel subpopulation of B cells, are a significant area of research due to their immune regulatory function in the immunological response. Bregs have been reported to regulate acute inflammation and immunity through the production of anti-inflammatory cytokines.

MATERIAL AND METHODS

A B cell subpopulation was identified using flow cytometric analysis in two different processes: 1) after preparation and storage of peripheral blood mononuclear cells (PBMCs) using Ficoll density gradient centrifugation from a human blood sample, 2) followed by isolation and storage of B cells through magnetic separation using a B cell isolation kit and MS column. ELISA assays were performed to observe the cytokine production of interkleukin 10 (IL-10) and transforming growth factor β₁ (TGF-β₁) by this novel B cell subpopulation.

RESULTS

Double positive staining of CD5+CD1d+ Bregs represents (19.27 ±1.52) from PBMCs, (33.32 ±2.95) from B cells accordingly (n = 40). Through ELISA assays, it has been found that B cell subpopulation produces IL-10 (0.56 ±0.08) and TGF-β₁ (0.90 ±0.12) (n = 40).

CONCLUSIONS

These methods should be able to facilitate progress in research on Bregs through the following steps: 1) the regulatory role may be observed in comparison with particular autoimmune diseases, inflammation, cancer, and immunologic responses to find out whether Breg alteration and/or cytokine production is altered as well in these disorders or conditions. 2) If the alteration of Bregs and cytokine production is significant along with the clinical correlation, a further in vitro study can be initiated with exposure of certain drugs to overcome the alteration of the cytokine production; then, an in vivo study can be initiated.

HBV-Induced Immune Imbalance in the Development of HCC

Chronic hepatitis B virus (HBV) infection is one of the high-risk factors for human HCC. Despite the integration of virus DNA and the oncoprotein HBx, chronic necroinflammation and hepatocellular regeneration account for hepatocarcinogenesis. As a non-cytopathic virus, HBV is extensively recognized to mediate chronic liver damage through abnormal immune attack. However, the mechanisms driving HBV infection to HCC are poorly understood. During chronic HBV infection in humans, the adaptive immunity changes from immune tolerance to progressive immune activation, inactivation, reactivation and exhaustion, all of which may be the immune pathogenic factors for the development of HCC. Recently, the immunopathogenic mechanisms were described in mouse HBV-induced HCC models, which is absolutely dependent on the presence of HBV-specific T cell response and NK cell-derived IFN-γ, findings which are consistent with the observations from CHB and HCC patients. In this review, we summarize recent research progression on the HBV-specific CD8⁺ T cells, and also CD4⁺ T cells, B cells and non-specific immune cells and molecules underlying chronic HBV infection and eventual HCC development to demonstrate the pathogenesis of HBV-induced immune imbalance. Based on the progression, we discussed the potential of immune-based therapies and their challenges in the treatment of HBV-related HCC, including the checkpoint inhibition, genetically modified T cell transfer, therapeutic vaccines and metabolic modulation.

Increased killer B cells in chronic HCV infection may lead to autoimmunity and increased viral load

Regulatory B (B_reg ) cells are characterized by various membrane markers and the secretion of different inhibitory cytokines. A new subset of B_reg cells was identified as CD5^hi Fas-ligand (FasL)^hi . Their main reported role is to suppress anti-viral and anti-tumour immune responses, and, hence they have been dubbed 'killer' B cells. In this study, we aim to assess the role of these cells in chronic hepatitis C virus (HCV) infection, and determine if they contribute to the increased viral load and persistence of HCV and its related autoimmunity. (i) FasL expression on CD5^hi B cells is increased significantly in HCV-infected patients compared to healthy individuals [28·06 ± 6·71 mean fluorescence intensity (MFI) ± standard error of the mean (s.e.m.), median = 27·9 versus 10·87 ± 3·97 MFI ± s.e.m., median = 10·3, respectively, P <  0·0001]. (ii) Killer B cells from HCV patients increased autologous CD4⁺ T cell apoptosis compared to the apoptosis in healthy individuals [39·17% ± 7·18% mean ± standard deviation (s.d.), median = 39·6 versus 25·92 ± 8·65%, mean ± s.d., median = 24·1%, P <  0·0001, respectively]. A similar increase was observed in CD8⁺ T cell apoptosis (54·67 ± 15·49% mean ± s.d., median = 57·3 versus 21·07% ± 7·4%, mean ± s.d., median = 20%, P = 0·0006, respectively). (iii) By neutralizing FasL with monoclonal anti-FasL antibodies, we have shown that the induction of apoptosis by killer B cells is FasL-dependent. (iv) Increased expression of FasL on CD5^hi B cells is correlated positively with an increased viral load and the presence of anti-nuclear antibodies and rheumatoid factor in HCV. This is the first study in which killer B cells have been suggested to play a pathogenic role in HCV. They seem to be involved in HCV's ability to escape efficient immune responses.

T follicular regulatory cells infiltrate the human airways during the onset of acute respiratory distress syndrome and regulate the development of B regulatory cells

T follicular regulatory (Tfr) cell is a CXCR5⁺Foxp3⁺ subset of T regulatory (Treg) cell with critical roles in regulating germinal center responses and modulating the immune environment in the lymph nodes. Studies have shown that the proportion of Tfr cells may increase during acute inflammation. In this study, we investigated the role of Tfr cells in acute respiratory distress syndrome (ARDS). We found that Tfr cells were significantly enriched in peripheral blood and in mini-bronchoalveolar lavage (BAL) during the onset of ARDS. Notably, Tfr cells represented the majority of Treg cells in the mini-BAL samples. Tfr cells also showed CTLA-4, IL-10, and TGF-β expression, but compared to the non-Tfr Treg cells, the CTLA-4 and IL-10 expression by Tfr cells were slightly reduced. Both Tfr cells and non-Tfr Treg cells suppressed the proliferation of autologous CD4⁺CD25⁻ T cells; however, the Tfr cells displayed slightly reduced suppression capacity. Subsequently, B cells were co-incubated with autologous Tfr cells or non-Tfr Treg cells. Interestingly, we found that the frequency of IL-10⁺ Breg cells was significantly higher following incubation with Tfr cells than with non-Tfr Treg cells, which suggested that Tfr cells were more potent at inducing IL-10⁺ Breg cells. Together, these results demonstrated that Tfr cells were a similar but distinctive subset of Treg cells. Given that Tfr cells were strongly enriched in ARDS patients, especially in the lung infiltrates, they may exert critical ameliorating effects in ARDS.

Elevated LAG-3 on CD4+ T cells negatively correlates with neutralizing antibody response during HCV infection

Lymphocyte activation gene-3 (LAG-3), an inhibitory molecule, which has been shown co-expressed with multiple inhibitory receptors on CD8⁺ T and natural killer (NK) cells and negatively regulates T and NK cell responses during hepatitis C virus (HCV) infection. However, whether LAG-3 is involved in the regulation of the antibody response remains unclear. This study aims to investigate the relationship of LAG-3 with neutralizing antibody (nAb) response during HCV infection. A total of 66 HCV-infected individuals and 36 sex- and age-matched healthy controls from a population of intravenous drug users were recruited. Circulating follicular helper T (cTfh) cells and LAG-3-expressing CD4⁺ T cells, type 1 regulatory T (Tr1) cells, and regulatory T (Treg) cells were characterized by flow cytometry. Serum nAb response of HCV-infected individuals was determined using pseudoparticle neutralization assays. We found that HCV infection enhanced LAG-3 expression on CD4⁺ T cells and exhibited regulatory T cell-like phenotype and inversely associated with the HCV nAb response. Further analysis showed that frequency of CXCR3⁺ cTfh cells positively correlated with nAb response, however LAG-3⁺ CD4⁺ T cells inversely associated with CXCR3⁺ cTfh cells. This study observed that LAG-3⁺ CD4⁺ T cells exhibit a regulatory cell phenotype and negatively associate with the HCV nAb response, implying that LAG-3 may be involved in the negative regulation of humoral immunity during HCV infection.

Research Progress on Regulatory B Cells in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic, systemic, autoimmune inflammatory disease characterized by the production of numerous autoantibodies and cytokines, as well as multiple organ damage. Specific B cell subsets negatively regulate immune responses and have been termed regulatory B cells (Bregs). Bregs are characterized by the production of the immunoregulatory cytokines interleukin (IL)-10, IL-35, and transforming growth factor (TGF)-β. Bregs suppress other immune cells through the secretion of these immunosuppressive cytokines and have thus been studied extensively for their potential role in the treatment of various autoimmune diseases. The progress of the research on Bregs and SLE in recent years is reviewed in this paper.

T Follicular Regulatory Cells and Antibody Responses in Transplantation

De novo donor-specific antibody (DSA) formation is a major problem in transplantation, and associated with long-term graft decline and loss as well as sensitization, limiting future transplant options. Forming high-affinity, long-lived antibody responses involves a process called the germinal center (GC) reaction, and requires interaction between several cell types, including GC B cells, T follicular helper (Tfh) and T follicular regulatory (Tfr) cells. T follicular regulatory cells are an essential component of the GC reaction, limiting its size and reducing nonspecific or self-reactive responses.An imbalance between helper function and regulatory function can lead to excessive antibody production. High proportions of Tfh cells have been associated with DSA formation in transplantation; therefore, Tfr cells are likely to play an important role in limiting DSA production. Understanding the signals that govern Tfr cell development and the balance between helper and regulatory function within the GC is key to understanding how these cells might be manipulated to reduce the risk of DSA development.This review discusses the development and function of Tfr cells and their relevance to transplantation. In particular how current and future immunosuppressive strategies might allow us to skew the ratio between Tfr and Tfh cells to increase or decrease the risk of de novo DSA formation.

Low Expression of IL-10 in Circulating Bregs and Inverted IL-10/TNF-α Ratio in Tears of Patients with Perennial Allergic Conjunctivitis: A Preliminary Study

Allergic conjunctivitis (AC) is one of the most common ophthalmological disorders seen in clinical practice. Growing evidence from recent years suggests that a subset of IL-10-expressing B cells is involved in inflammatory allergic diseases. In this study, we aimed to evaluate the potential involvement of blood Bregs cells in perennial allergic conjunctivitis (PAC), and interleukins (IL)-1β, IL-6, IL-8, IL-10, and IL-12, and tumor necrosis factor (TNF)-α, were measured in tear samples and compared with healthy controls (HC) using flow cytometry. Non-significant differences in CD19⁺IL-10⁺ cell frequency between PAC patients and healthy controls (HC) were observed. Nevertheless, when we analyzed the mean fluorescence intensity (MFI) of IL-10 on CD19⁺CD38^Lo/Med/Hi-gated cells, we observed a significant decrease in MFI in all Bregs subsets in PAC patients. Additionally, tear cytokines showed 2.8 times lower levels of IL-10 than TNF-α in PAC patients when compared to HC. Our findings demonstrate an immunological dysregulation in patients with allergic conjunctivitis, characterized by the low expression of IL-10 in circulating CD19⁺CD38⁺ Bregs subsets and an inverted tear IL-10/TNF-α ratio, promoting a local pro-inflammatory microenvironment. These findings highlight the novel pathologic changes involved in ocular allergic diseases. Understanding systemic and local mechanisms will aid the design of immunomodulating therapeutics at different levels.

Baicalin ameliorates lupus autoimmunity by inhibiting differentiation of Tfh cells and inducing expansion of Tfr cells

Baicalin is a natural compound isolated from Chinese herb, which has been reported as an anti-inflammatory drug. Here, we demonstrated that Baicalin treatment could reduce urine protein, inhibit anti-ds-DNA antibody titers, and ameliorate lupus nephritis in MRL/lpr lupus-prone mice. Baicalin inhibited Tfh cell differentiation and IL-21 production, but promoted Foxp3⁺ regulatory T cell differentiation including part of follicular regulatory T (Tfr) cells. Intravenous injection of Baicalin-induced Foxp3⁺ regulatory T cells could relieve nephritis, inhibit Tfh cell differentiation and IL-21 production. Baicalin inhibited mTOR activation, reduced mTOR agonist-mediated Tfh cell expansion and increased Tfr cells. These data suggest that Baicalin attenuates lupus autoimmunity by up- and downregulating the differentiation of Tfr cells and Tfh cells, respectively. Baicalin and ex vivo expanded Foxp3⁺ regulatory T cells are promising therapeutics for the treatment of lupus.

Follicular regulatory T cells infiltrated the ovarian carcinoma and resulted in CD8 T cell dysfunction dependent on IL-10 pathway

A high Treg/CD8 T cell ratio in ovarian carcinoma was negatively associated with the prognosis of the patients. The human follicular regulatory T (Tfr) cells are a newly characterized subset of Treg cells with features of both follicular helper T (Tfh) cells (CXCR5⁺) and canonical Treg cells (CD25⁺Foxp3⁺). The role of Tfr cells in ovarian cancer is yet unclear. We found that in peripheral blood, the ovarian cancer patients presented significantly higher levels of both CD4⁺CD25⁺CD127^-CXCR5⁺ T cells and CD4⁺CD25⁺CD127^-CXCR5⁺Foxp3⁺ T cells than the healthy controls. In resected tumor samples, Tfr cells represented a much greater percentage of lymphocytes than in peripheral blood. Interestingly, the circulating Tfr cells from ovarian cancer patients presented significantly higher TGFB1 and IL10 expression than their counterparts in healthy controls directly ex vivo, and significantly higher IL10 after stimulation. The tumor-infiltrating Tfr cells presented further upregulated expression of TGFB1 and IL10. In addition, the levels of TGFB1 and IL10 expression by Tfr cells negatively associated with the expression of IFNG in tumor-infiltrating CD8 T cells. In an in vitro CD8 T cell/Tfr cell coculture system, we found that Tfr cells could significantly suppress the activation of CD8 T cells, in a manner that was dependent on IL-10 and probably on TGF-β. Overall, our study found that Tfr cells could suppress CD8 T cells, and in ovarian cancer patients, the Tfr cells were increased in both frequency and function.

HCV-associated exosomes promote myeloid-derived suppressor cell expansion via inhibiting miR-124 to regulate T follicular cell differentiation and function

Virus-infected cells can regulate non-permissive bystander cells, but the precise mechanisms remain incompletely understood. Here we report that this process can be mediated by transfer of viral RNA-loaded exosomes shed from infected cells to myeloid-derived suppressor cells (MDSCs), which in turn regulate the differentiation and function of T cells during viral infection. Specifically, we demonstrated that patients with chronic hepatitis C virus (HCV) infection exhibited significant increases in T follicular regulatory (TFR) cells and decreases in T follicular helper (TFH) cells. These MDSC-mediated T-cell dysregulations resulted in an increased ratio of TFR/TFH and IL-10 production in peripheral blood. Specifically, co-culture of MDSCs derived from HCV patients with healthy peripheral blood mononuclear cells (PBMCs) induced expansion of TFR, whereas depletion of MDSCs from PBMCs of HCV patients reduced the increases in TFR frequency and IL-10 production, and promoted the differentiation of IFN-γ-producing TFH cells. Importantly, we found that exosomes isolated from the plasma of HCV patients and supernatant of HCV-infected hepatocytes could drive monocytic myeloid cell differentiation into MDSCs. These exosomes were enriched in tetraspanins, such as CD63 and CD81, and contained HCV RNA, but exosomes isolated from patients with antiviral treatment contained no HCV RNA and could not induce MDSC differentiation. Notably, these HCV RNA-containing exosomes (HCV-Exo) were sufficient to induce MDSCs. Furthermore, incubation of healthy myeloid cells with these HCV-Exo inhibited the expression of miR-124, whereas reconstitution of PBMCs with miR-124 abolished the effects of HCV-Exo on MDSC induction. Taken together, these results indicate that HCV-associated exosomes can transfer immunomodulatory viral RNA from infected cells to neighboring immune cells and trigger MDSC expansion, which subsequently promotes TFR differentiation and inhibits TFH function. This study reveals a previously unrecognized path that represents a novel mechanism of immune dysregulation during chronic viral infection.

Control of Germinal Center Responses by T-Follicular Regulatory Cells

Regulatory T-cells (Treg cells), expressing the transcription factor Foxp3, have an essential role in the control of immune homeostasis. In order to control diverse types of immune responses Treg cells must themselves show functional heterogeneity to control different types of immune responses. Recent advances have made it clear that Treg cells are able to mirror the homing capabilities of known T-helper subtypes such as Th1, Th2, Th17, and T-follicular helper cells (Tfh), allowing them to travel to the sites of inflammation and deliver suppression in situ. One of the more recent discoveries in this category is the description of T-follicular regulatory (Tfr) cells, a specialized subset of Treg cells that control Tfh and resulting antibody responses. In this review we will discuss recent advances in our understanding of Tfr biology and the role of both Tfr and activated extra-follicular Tregs (eTreg) in the control of humoral immunity.

Several Follicular Regulatory T Cell Subsets With Distinct Phenotype and Function Emerge During Germinal Center Reactions

An efficient B cell immunity requires a dynamic equilibrium between positive and negative signals. In germinal centers (GCs), T follicular helper cells are supposed to be the positive regulator while T follicular regulatory (Tfr) cells were assigned to be the negative regulators. Indeed, Tfr cells are considered as a homogenous cell population dedicated to dampen the GC extent. Moreover, Tfr cells prevent autoimmunity since their dysregulation leads to production of self-reactive antibodies (Ab). However, a growing corpus of evidence has revealed additional and unexpected functions for Tfr cells in the regulation of B cell responses. This review provides an overview of the Tfr cell contribution and presents Tfr cell proprieties in the context of vaccination.

The prevalence and function of CD4+CXCR5+Foxp3+ follicular regulatory T cells in diffuse large B cell lymphoma

CD4⁺CXCR5⁺Foxp3⁺ follicular regulatory T (Tfr) cells possess critical roles in suppressing the germinal center reaction, B cell activation, and follicular helper T cell (Tfh) cytokine secretion. Since diffuse large B cell lymphoma (DLBCL) can arise from B cells undergoing germinal center reaction and/or differentiation, we hypothesized that Tfr cells might be involved in DLBCL. In the present study, we recruited thirty-five DLBCL patients and twenty-five healthy controls. Data showed that DLBCL patients presented an enrichment of circulating CD4⁺CXCR5⁺Foxp3⁺ Tfr cells compared to controls. In the primary tumor isolated from enlarged lymph nodes, Tfr cells made up of roughly 3% to 16% of infiltrating T cells. Higher levels of tumor-infiltrating Tfr cells were observed in patients with less advanced DLBCL stages, and in patients that stayed in remission 24 months after the initial R-CHOP treatment. High BCL6 and high FOXP3 expression was observed in Tfr cells ex vivo. After anti-CD3/CD28 and IL-2 stimulation, the Tfr cells more closely resembled Treg cells and presented high IL10 and TGFB1 expression. CD4⁺CD25⁺CXCR5⁺ Tfr cells and CD4⁺CD25⁺CXCR5^- non-Tfr Treg cells could suppress CD4⁺CD25^- Tconv cell and CD8⁺ T cell proliferation with similar capacity. However, Tfr cells were less capable of suppressing IFNG expression than Treg cells, and although both cell types supported CD19⁺ tumor cell proliferation, Tfr cells were less supportive than the non-Tfr Treg cells. Overall, this study suggested that Tfr cells were involved in intratumoral immunity, were likely beneficial to DLBCL patients, and were functionally distinctive from non-Tfr Treg cells. The distribution pattern and the prognostic value of Tfr cells in DLBCL should be examined in further studies.

The Janus Face of Follicular T Helper Cells in Chronic Viral Infections

Chronic infections with non-cytopathic viruses constitutively expose virus-specific adaptive immune cells to cognate antigen, requiring their numeric and functional adaptation. Virus-specific CD8 T cells are compromised by various means in their effector functions, collectively termed T cell exhaustion. Alike CD8 T cells, virus-specific CD4 Th1 cell responses are gradually downregulated but instead, follicular T helper (T_FH) cell differentiation and maintenance is strongly promoted during chronic infection. Thereby, the immune system promotes antibody responses, which bear less immune-pathological risk compared to cytotoxic and pro-inflammatory T cell responses. This emphasis on T_FH cells contributes to tolerance of the chronic infection and is pivotal for the continued maturation and adaptation of the antibody response, leading eventually to the emergence of virus-neutralizing antibodies, which possess the potential to control the established chronic infection. However, sustained high levels of T_FH cells can also result in a less stringent B cell selection process in active germinal center reactions, leading to the activation of virus-unspecific B cells, including self-reactive B cells, and to hypergammaglobulinemia. This dispersal of B cell help comes at the expense of a stringently selected virus-specific antibody response, thereby contributing to its delayed maturation. Here, we discuss these opposing facets of T_FH cells in chronic viral infections.

Viral envelope-specific antibodies in chronic hepatitis B virus infection

While the cellular immune response associated with acute and chronic HBV infection has been thoroughly studied, the B cell response in chronic hepatitis B and the role of antibodies raised against the HBV envelope antigens in controlling and prevention of infection requires further investigation. The detection of anti-HBs antibodies is considered as one of the biomarkers for functional cure of chronic hepatitis B virus infection, as well as for protective immunity. Indeed, vaccine-induced neutralizing anti-HBs antibodies have been shown to protect against HBV challenge. Yet, the therapeutic potential of viral envelope-specific antibodies and the mechanism involved in protection and prevention of cell-to-cell transmission warrants additional investigative efforts. In this review, we will provide a critical overview of the available preclinical and clinical literature supporting the putative role of active and passive vaccination and neutralizing envelope-specific antibodies for therapeutic intervention in combination regimens intended to cure persistent HBV infection.

Hepatocyte-derived exosomes promote T follicular regulatory cell expansion during hepatitis C virus infection

Hepatitis C virus (HCV) is a global health concern that can cause severe liver disease, such as cirrhosis and hepatocellular carcinoma. Control of HCV requires vigorous T-cell responses, yet CD4⁺ T cells in chronic HCV patients are dysfunctional. T follicular regulatory (Tfr) cells are a subset of regulatory T cells that suppress T follicular helper (Tfh) cells and the generation of high affinity antibody-producing B cells. In this study, we examined the accumulation of Tfr cells in the liver compartment during chronic HCV infection and defined the cellular and molecular mechanisms underlying their expansion. Our analysis revealed a substantial population of Tfr cells in livers of chronic HCV patients that is absent in liver tissues from nonviral hepatitis or healthy subjects. Coculture of PBMCs from healthy subjects with HCV-infected hepatoma cells resulted in preferential expansion of circulating Tfr cells, leading to suppression of Tfh cells. Additionally, coculture of tonsillar cells with infected hepatoma cells lead to an expansion of germinal center Tfr. Notably, expansion was mediated by transforming growth factor beta (TGF-β)-containing exosomes released from HCV-infected hepatocytes given that blockade of exosome-associated TGF-β or inhibition of exosome release abrogated Tfr expansion.

CONCLUSION

These results show that liver-derived exosomes play a pivotal role in the accumulation of Tfr cells, likely leading to suppression of Tfh responses in HCV-infected patients. Our study identifies a novel pathway in which HCV infection in hepatocytes exacerbates Tfr cell responses to subvert antiviral immunity. (Hepatology 2018;67:71-85).

Increased proportions of B cells with spontaneous production of interleukin-10 in HIV-infected individuals are normalized during combination antiretroviral therapy: a longitudinal study

Interleukin-10 (IL-10)-producing B cells (B10 cells) may inhibit HIV-specific T cells and are elevated in untreated HIV infection. We aimed to determine the effect of combination antiretroviral treatment (cART) on the proportion of B10 cells. Furthermore, we compared B10-cell proportions in HIV-infected progressors and viremic controllers. This was a prospective study including HIV-infected progressors, viremic controllers and healthy controls. Progressors initiating cART were followed for 6 months. Purified B cells were stimulated with CpG, alone or in combination with HIV gp120, and the proportion of B10 cells was measured by flow cytometry. Without stimulation, the B10-cell proportion was higher in progressors than in healthy controls, while viremic controllers and healthy controls had comparable proportions. Moreover, the proportion of CD24^hi CD38^hi transitional B cells was higher in progressors than in healthy controls. After initiation of cART, the proportion of B10 cells and transitional B cells decreased. In conclusion, progressors had elevated B10-cell proportions, while viremic controllers displayed normal proportions. After initiation of cART, the B10-cell proportion decreased. This could limit B10-cell-mediated suppression of specific CD8⁺ T-cell responses.

Interaction effects among IFN-γ+874, IL-2-330, IL-10-1082, IL-10-592 and IL-4-589 polymorphisms on the clinical progression of subjects infected with hepatitis B virus and/or hepatitis C virus: a retrospective nested case-control study

BACKGROUND

The natural outcomes of hepatitis B virus (HBV) and/or hepatitis C virus (HCV) infections vary considerably among individuals The infection may heal naturally, or patients may succumb to chronic liver diseases, including chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. The mechanism is not fully understood.

OBJECTIVES

To evaluate the interaction among four single nucleotide polymorphisms (SNPs) and their influence on different clinical outcomes.

METHODS

277 individuals infected with HBV and/or HCV, including 81 patients with chronic hepatitis B and C, 122 asymptomatic HBV and/or HCV carriers and 74 controls who cleared HBV and HCV spontaneously, were involved in this study. The SNPs of four genes (rs2069762/-330 G/T of IL-2, rs2430561/+874A>T of IFN-γ, rs1800896/-1082G>A and rs1800872/-592C>A of IL-10 and rs2243250/-589C>T of IL-4) were analysed using restriction fragment length polymorphism-polymerase chain reaction or sequence-specific primer PCR. The gene-gene interactions were assessed using the multifactor-dimensionality reduction method.

RESULTS

Interleukin (IL)-10-592 AC and IL-4-589 CC/CT showed a synergistic effect on liver inflammatory injury (p<0.01), whereas interferon (IFN)-γ+874  AA and IL-2-330 TT had a synergistic impact (p<0.05). IFN-γ+874  AA and IL-10-1082 AA had an antagonistic effect (p<0.01) on the clinical progression, including asymptomatic HBV and HCV carriers and chronic hepatitis. IL-2-330 TT and IL-10-1082 AA synergistically influenced the clinical outcome (p<0.05). IFN-γ+874 AA, IL-2-330 TT and IL-10-1082 AA interactively affected the clinical outcome including asymptomatic HBV and HCV carriers and chronic hepatitis (p<0.05).

CONCLUSIONS

Interactions among polymorphisms of IFN-γ+874 AA, IL-2-330 TT, IL-10-1082 AA, IL10--592 AC and IL-4-589 CC/CT significantly influenced the clinical progression of the subjects with HBV and/or HCV infection.

Human blood Tfr cells are indicators of ongoing humoral activity not fully licensed with suppressive function

Germinal center (GC) responses are controlled by T follicular helper (Tfh) and T follicular regulatory (Tfr) cells and are crucial for the generation of high-affinity antibodies. Although the biology of human circulating and tissue Tfh cells has been established, the relationship between blood and tissue Tfr cells defined as CXCR5+Foxp3+ T cells remains elusive. We found that blood Tfr cells are increased in Sjögren syndrome, an autoimmune disease with ongoing GC reactions, especially in patients with high autoantibody titers, as well as in healthy individuals upon influenza vaccination. Although blood Tfr cells correlated with humoral responses, they lack full B cell-suppressive capacity, despite being able to suppress T cell proliferation. Blood Tfr cells have a naïve-like phenotype, although they are absent from human thymus or cord blood. We found that these cells were generated in peripheral lymphoid tissues before T-B interaction, as they are maintained in B cell-deficient patients. Therefore, blood CXCR5+Foxp3+ T cells in human pathology indicate ongoing humoral activity but are not fully competent circulating Tfr cells.

T follicular regulatory cells in mice and men

It has long been known that CD4 T cells are necessary to provide help to B cells, triggering a germinal centre (GC) reaction where affinity maturation and isotype switching occur. However, the nature of the dedicated CD4 helper T cells, known as T follicular helper (Tfh), was only recently described. Here, we review the biology and function of the recently described T follicular regulatory (Tfr) cells, another CD4 T-cell population also found within GCs but with regulatory function and characteristics. Tfr cells have been identified in mice and humans as simultaneously presenting characteristics of T follicular cells (namely CXCR5 expression) and regulatory T cells (including Foxp3 expression). These Tfr cells have been implicated in the regulation of the magnitude of the GC reaction, as well as in protection from immune-mediated pathology.

From dendritic cells to B cells dysfunctions during HIV-1 infection: T follicular helper cells at the crossroads

T follicular helper (Tfh) cells are essential for B-cell differentiation and the subsequent antibody responses. Their numbers and functions are altered during human and simian immunodeficiency virus (HIV/SIV) infections. In lymphoid tissues, Tfh cells are present in germinal centre, where they are the main source of replicative HIV-1 and represent a major reservoir. Paradoxically, Tfh cell numbers are increased in chronically infected individuals. Understanding the fate of Tfh cells in the course of HIV-1 infection is essential for the design of efficient strategies toward a protective HIV vaccine or a cure. The purpose of this review is to summarize the recent advance in our understanding of Tfh cell dynamics during HIV/SIV infection. In particular, to explore the possible causes of their expansion in lymphoid tissues by discussing the impact of HIV-1 infection on dendritic cells, to identify the molecular players rendering Tfh cells highly susceptible to HIV-1 infection, and to consider the contribution of regulatory follicular T cells in shaping Tfh cell functions.

Immune perturbations in HIV-1-infected individuals who make broadly neutralizing antibodies

Induction of broadly neutralizing antibodies (bnAbs) is a goal of HIV-1 vaccine development. bnAbs occur in some HIV-1-infected individuals and frequently have characteristics of autoantibodies. We have studied cohorts of HIV-1-infected individuals who made bnAbs and compared them with those who did not do so, and determined immune traits associated with the ability to produce bnAbs. HIV-1-infected individuals with bnAbs had a higher frequency of blood autoantibodies, a lower frequency of regulatory CD4+ T cells, a higher frequency of circulating memory T follicular helper CD4+ cells, and a higher T regulatory cell level of programmed cell death-1 expression compared with HIV-1-infected individuals without bnAbs. Thus, induction of HIV-1 bnAbs may require vaccination regimens that transiently mimic immunologic perturbations in HIV-1-infected individuals.

Role of regulatory b cells in neuroimmunologic disorders

B lymphocytes augment the immune response by producing antibodies and activating T cells by antigen presentation. Recent studies have highlighted a specific and functionally significant B‐cell subset that could downregulate excessive immune and inflammatory responses through a vast array of inhibitory cytokines, such as interleukin (IL)‐10 and transforming growth factor‐β (TGF‐β). This subset of B cells is generally referred to as regulatory B cells (Bregs). In addition, recent studies have shown that IL‐35‐producing Bregs also play a role in downregulation of immunity. Diverse phenotypes of Bregs have been proposed to underlie human disorders and their animal models. Most studies have focused on the role of different subsets of Bregs and Bregs‐associated molecules such as IL‐10, TGF‐β, and IL‐35 in the pathogenesis of neuroimmunologic disorders. Furthermore, Bregs exert regulatory function mainly through suppressing the differentiation of Th1/Th17 cells and promoting regulatory T‐cell expansion. Reduced presence of Bregs is reportedly associated with progression of several neuroimmunologic disorders. This Review summarizes the current knowledge on the role of Bregs in neuroimmunologic disorders, including multiple sclerosis, neuromyelitis optica, and myasthenia gravis. © 2016 The Authors. Journal of Neuroscience Research Published by Wiley Periodicals, Inc.