Early IL-17 production by intrahepatic T cells is important for adaptive immune responses in viral hepatitis

MiR-326 sponges TET2 triggering imbalance of Th17/Treg differentiation to exacerbate pyroptosis of hepatocytes in concanavalin A-induced autoimmune hepatitis

INTRODUCTION AND OBJECTIVES

MicroRNA-326 is abnormally expressed in autoimmune diseases, but its roles in autoimmune hepatitis (AIH) are unknown. In this study, we aimed to investigate the effect of miR-326 on AIH and the underlying mechanism.

MATERIALS AND METHODS

Concanavalin A was administrated to induce AIH in mice and the expression levels of miR-326 and TET2 was evaluated by qRT-PCR and western blot, respectively. The percentages of Th17 and Treg cells were evaluated by flow cytometry and their marker proteins were determined by western blot and ELISA. The mitochondrial membrane potential (MMP) and ROS level were tested with the JC-1 kit and DCFH-DA assay. The binding relationships between miR-326 and TET2 were verified by dual-luciferase reporter assay. The liver tissues were stained by the HE staining. In vitro, AML12 cells were cocultured with mouse CD4+T cells. The expression levels of pyroptosis-related proteins were assessed by western blot.

RESULTS

Concanavalin A triggered AIH and enhanced the expression level of miR-326 in mice. It increased both Th17/Treg ratio and the levels of their marker proteins. The expression of TET2 was decreased in AIH mice. Knockdown of miR-326 could decrease the levels of pyroptosis-related proteins, the ROS level and increase MMP. In mouse CD4+T cells, miR-326 sponged TET2 to release IL-17A. Coculture of AML12 cells with isolated CD4+T cells from miR-326 knockdown AIH mice could relieve pyroptosis.

CONCLUSIONS

Knockdown of miR-326 exerted anti-pyroptosis effects via suppressing TET2 and downstream NF-κB signaling to dampen AIH. We highlighted a therapeutic target in AIH.

Infiltrated IL-17A-producing gamma delta T cells play a protective role in sepsis-induced liver injury and are regulated by CCR6 and gut commensal microbes

Introduction

Sepsis is a common but serious disease in intensive care units, which may induce multiple organ dysfunctions such as liver injury. Previous studies have demonstrated that gamma delta (γδ) T cells play a protective role in sepsis. However, the function and mechanism of γδ T cells in sepsis-induced liver injury have not been fully elucidated. IL-17A-producing γδ T cells are a newly identified cell subtype.

Methods

We utilized IL-17A-deficient mice to investigate the role of IL-17A-producing γδ T cells in sepsis using the cecum ligation and puncture (CLP) model.

Results

Our findings suggested that these cells were the major source of IL-17A and protected against sepsis-induced liver injury. Flow cytometry analysis revealed that these γδ T cells expressed Vγ4 TCR and migrated into liver from peripheral post CLP, in a CCR6-dependent manner. When CLP mice were treated with anti-CCR6 antibody to block CCR6-CCL20 axis, the recruitment of Vγ4+ γδ T cells was abolished, indicating a CCR6-dependent manner of migration. Interestingly, pseudo germ-free CLP mice treated with antibiotics showed that hepatic IL-17A+ γδ T cells were regulated by gut commensal microbes. E. coli alone were able to restore the protective effect in pseudo germ-free mice by rescuing hepatic IL-17A+ γδ T cell population.

Conclusion

Our research has shown that Vγ4+ IL-17A+ γδ T cells infiltrating into the liver play a crucial role in protecting against sepsis-induced liver injury. This protection was contingent upon the recruitment of CCR6 and regulated by gut commensal microbes.

Engineering γδ T Cells: Recognizing and Activating on Their Own Way

Adoptive cell therapy (ACT) with engineered T cells has emerged as a promising strategy for the treatment of malignant tumors. Among them, there is great interest in engineered γδ T cells for ACT. With both adaptive and innate immune characteristics, γδ T cells can be activated by γδ TCRs to recognize antigens in a MHC-independent manner, or by NK receptors to recognize stress-induced molecules. The dual recognition system enables γδ T cells with unique activation and cytotoxicity profiles, which should be considered for the design of engineered γδ T cells. However, the current designs of engineered γδ T cells mostly follow the strategies that used in αβ T cells, but not making good use of the specific characteristics of γδ T cells. Therefore, it is no surprising that current engineered γδ T cells in preclinical or clinical trials have limited efficacy. In this review, we summarized the patterns of antigen recognition of γδ T cells and the features of signaling pathways for the functions of γδ T cells. This review will additionally discuss current progress in engineered γδ T cells and provide insights in the design of engineered γδ T cells based on their specific characteristics.

Interleukin-17A pretreatment attenuates the anti-hepatitis B virus efficacy of interferon-alpha by reducing activation of the interferon-stimulated gene factor 3 transcriptional complex in hepatitis B virus-expressing HepG2 cells

Background

Some cytokine signaling pathways can interact with interferon (IFN)-α pathway and thus regulate cell responses to IFN-α. Levels of the pro-inflammatory cytokine interleukin-17A (IL-17A) were found to be elevated in both the peripheral blood and liver in chronic hepatitis B (CHB) patients. However, how IL-17A affects the anti-HBV activity of IFN-α remains unclear.

Methods

The effects of IL-17A on anti-HBV activity of IFN-α were evaluated in HBV-expressing HepG2 cells (HepG2-HBV1.3) with IL-17A pretreatment and IFN-α stimulation. Culture supernatant levels of HBsAg, HBeAg, and HBV DNA, or intracellular expression of HBsAg and HBcAg were detected by ELISA, real-time quantitative PCR (RT-qPCR), or western blotting (WB). The expression of canonical IFN-α signaling pathway components, including the interferon-α/β receptor (IFNAR), Janus Kinase 1 (JAK1), Tyrosine Kinase 2 (TYK2), the Interferon Stimulated Gene Factor 3 complex (ISGF3) and IFN-stimulated genes (ISGs), was also examined by RT-qPCR, Immunofluorescence or WB. The effects of IL-17A were further investigated by the suppression of the IL-17A pathway with a TRAF6 inhibitor.

Results

Compared to IFN-α stimulation alone, IL-17A pretreatment followed by IFN-α stimulation increased the levels of HBsAg, HBeAg, and HBV DNA, and decreased the levels of ISGF3 complex (phosphorylated (p)-signal transducer and activator of transcription (STAT1)/p-STAT2/IRF9) and antiviral-related ISGs (ISG15, ISG20 and Mx1). Interestingly, IL-17A pretreatment increased the expression of suppressor of cytokine signaling (SOCS) 1, SOCS3 and USP18, which were also the ISGs negatively regulating activity of ISGF3. Moreover, IFNAR1 protein expression declined more sharply in the group with IL-17A pretreatment than in the group with IFN-α stimulation alone. Blocking the IL-17A pathway reversed the effects of IL-17A on the IFN-α-induced activation of ISGF3 and anti-HBV efficacy.

Conclusions

Our results demonstrate that IL-17A pretreatment could attenuate IFN-α-induced anti-HBV activity by upregulating negative regulators of the critical transcriptional ISGF3 complex. Thus, this might be a potential target for improving response to IFN-α therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-022-01753-x.

Metformin Modulates T Cell Function and Alleviates Liver Injury Through Bioenergetic Regulation in Viral Hepatitis

Metformin is not only the first-line medication for the treatment of type 2 diabetes, but it is also effective as an anti-inflammatory, anti-oxidative and anti-tumor agent. However, the effect of metformin during viral hepatitis remains elusive. Using an adenovirus (Ad)-induced viral hepatitis mouse model, we found that metformin treatment significantly attenuated liver injury, with reduced serum aspartate transaminase (AST) and alanine transaminase (ALT) levels and liver histological changes, presumably via decreased effector T cell responses. We then demonstrated that metformin reduced mTORC1 activity in T cells from infected mice, as evidenced by decreased phosphorylation of ribosome protein S6 (p-S6). The inhibitory effects on the mTORC1 signaling by metformin was dependent on the tuberous sclerosis complex 1 (TSC1). Mechanistically, metformin treatment modulated the phosphorylation of dynamin-related protein 1 (Drp-1) and mitochondrial fission 1 protein (FIS1), resulting in increased mass in effector T cells. Moreover, metformin treatment promoted mitochondrial superoxide production, which can inhibit excessive T cell activation in viral hepatitis. Together, our results revealed a protective role and therapeutic potential of metformin against liver injury in acute viral hepatitis via modulating effector T cell activation via regulating the mTORC1 pathway and mitochondrial functions.

Hepatic lymphocytes involved in the pathogenesis of pediatric and adult non-alcoholic fatty liver disease

The immune response is critical in NAFLD pathogenesis, but the liver infiltrate's composition and the role of each T cell population is still up for debate. To characterize liver pathogenesis in pediatric and adult cases, frequency and localization of immune cell populations [Cytotoxic T Lymphocytes (CD8+), T helper Lymphocytes (CD4+), Regulatory T lymphocytes (Foxp3+) and Th17 (IL-17A+)] were evaluated. In portal/periportal (P/P) tracts, both age groups displayed a similar proportion of CD8+ and CD4+ lymphocytes. However, comparable Foxp3+ and IL-17A+ cell frequencies were observed in pediatric cases, meanwhile, in adults Foxp3+ was higher than IL-17A+ cells. Interestingly, IL-17A+ lymphocytes seemed to be nearly exclusive of P/P area in both age groups. In intralobular areas, both pediatric and adult cases showed CD8+ lymphocytes predominance with lower frequencies of CD4+ lymphocytes followed by Foxp3+ . Severe inflammation was associated with higher intralobular Foxp3+ lymphocytes (p = 0.026) in children, and lower P/P Foxp3+ and higher IL-17A+ lymphocytes in adults. All cases with fibrosis ≥ 2 displayed P/P low Foxp3+ and high IL-17A+ lymphocyte counts. Pediatric cases with worse steatosis showed high P/P CD4+ (p = 0.023) and intralobular CD8+ (p = 0.027) and CD4+ cells (p = 0.012). In NAFLD cases, the lymphocyte liver infiltrate composition differs between histological areas. Treg and Th17 balance seems to condition damage progression, denoting their important role in pathogenesis.

IL-17 in the Pathogenesis of Disease: Good Intentions Gone Awry

The IL-17 family is an evolutionarily old cytokine family consisting of six members (IL-17A through IL-17F). IL-17 family cytokines signal through heterodimeric receptors that include the shared IL-17RA subunit, which is widely expressed throughout the body on both hematopoietic and nonhematopoietic cells. The founding family member, IL-17A, is usually referred to as IL-17 and has received the most attention for proinflammatory roles in autoimmune diseases like psoriasis. However, IL-17 is associated with a wide array of diseases with perhaps surprisingly variable pathologies. This review focuses on recent advances in the roles of IL-17 during health and in disease pathogenesis. To decipher the functions of IL-17 in diverse disease processes it is useful to first consider the physiological functions that IL-17 contributes to health. We then discuss how these beneficial functions can be diverted toward pathogenic amplification of deleterious pathways driving chronic disease.

Interleukin-17A Facilitates Chikungunya Virus Infection by Inhibiting IFN-α2 Expression

Interferons (IFNs) are the key components of innate immunity and are crucial for host defense against viral infections. Here, we report a novel role of interleukin-17A (IL-17A) in inhibiting IFN-α2 expression thus promoting chikungunya virus (CHIKV) infection. CHIKV infected IL-17A deficient (Il17a^-/- ) mice expressed a higher level of IFN-α2 and developed diminished viremia and milder footpad swelling in comparison to wild-type (WT) control mice, which was also recapitulated in IL-17A receptor-deficient (Il17ra^-/- ) mice. Interestingly, IL-17A selectively blocked IFN-α2 production during CHIKV, but not West Nile virus (WNV) or Zika virus (ZIKV), infections. Recombinant IL-17A treatment inhibited CHIKV-induced IFN-α2 expression and enhanced CHIKV replication in both human and mouse cells. We further found that IL-17A inhibited IFN-α2 production by modulating the expression of Interferon Regulatory Factor-5 (IRF-5), IRF-7, IFN-stimulated gene 49 (ISG-49), and Mx1 expression during CHIKV infection. Neutralization of IL-17A in vitro leads to the increase of the expression of these antiviral molecules and decrease of CHIKV replication. Collectively, these results suggest a novel function of IL-17A in inhibiting IFN-α2-mediated antiviral responses during CHIKV infection, which may have broad implications in viral infections and other inflammatory diseases.

Interleukin-2 maintains the survival of interleukin-17+ gamma/delta T cells in inflammation and autoimmune diseases

There is increasing appreciation of the critical pathogenic role of IL-17 in inflammation and autoimmune diseases, which could be produced from both adaptive Th17 cells and innate γδ T cells. Existing evidences suggest that IL-2 is important for in vivo accumulation of IL-17⁺ γδ T cells, leaving the mechanisms still elusive. Herein, using lupus-prone MRL/lpr mice, we demonstrated that splenic γδ T cells were potent IL-17 producers at the onset of lupus, which could be diminished by in vivo IL-2 neutralization. Additional in vivo results showed that neutralization of IL-2 also significantly deleted the IL-17-producing γδ T cells in ovalbumin (OVA) /CFA-immunized B6 mice. Using splenic γδ T cells from OVA/CFA-immunized B6 mice, we further demonstrated that IL-2 could induce IL-17 production alone or together with IL-1β or IL-23 or anti-TCRγδ. Mechanism studies demonstrated that IL-2 could support the survival of γδ T cells, rather than induce the proliferation. Through specific pharmacologic inhibitor, we demonstrated that IL-2 could maintain that RORγt expression of γδ T cells in a STAT5-dependent manner. Collectively, this study suggested that the interplay between IL and 2 and other pro-inflammatory cytokines could trigger the rapid IL-17 production from innate γδ T cells, thus to orchestrate an inflammatory response before the development of adaptive Th17 cells.

γδ T Cells: The Ideal Tool for Cancer Immunotherapy

γδ T cells have recently gained considerable attention as an attractive tool for cancer adoptive immunotherapy due to their potent anti-tumor activity and unique role in immunosurveillance. The remarkable success of engineered T cells for the treatment of hematological malignancies has revolutionized the field of adoptive cell immunotherapy. Accordingly, major efforts are underway to translate this exciting technology to the treatment of solid tumors and the development of allogeneic therapies. The unique features of γδ T cells, including their major histocompatibility complex (MHC)-independent anti-cancer activity, tissue tropism, and multivalent response against a broad spectrum of the tumors, render them ideal for designing universal 'third-party' cell products, with the potential to overcome the challenges of allogeneic cell therapy. In this review, we describe the crucial role of γδ T cells in anti-tumor immunosurveillance and we summarize the different approaches used for the ex vivo and in vivo expansion of γδ T cells suitable for the development of novel strategies for cancer therapy. We further discuss the different transduction strategies aiming at redirecting or improving the function of γδ T cells, as well as, the considerations for the clinical applications.

IL-17A activated by Toll-like receptor 9 contributes to the development of septic acute kidney injury

Toll-like receptor 9 (TLR9), which is activated by endogenously released mtDNA during sepsis, contributes to the development of polymicrobial septic acute kidney injury (AKI). However, downstream factors of TLR9 to AKI remain unknown. We hypothesized that IL-17A activated by TLR9 may play a critical role in septic AKI development. To determine the effects of TLR9 on IL-17A production in septic AKI, we used a cecal ligation and puncture (CLP) model in Tlr9 knockout (Tlr9KO) mice and wild-type (WT) littermates. We also investigated the pathway from TLR9 activation in dendritic cells (DCs) to IL-17A production by γδT cells in vitro. To elucidate the effects of IL-17A on septic AKI, Il-17a knockout (Il-17aKO) mice and WT littermates were subjected to CLP. We further investigated the relationship between the TLR9-IL-17A axis and septic AKI by intravenously administering recombinant IL-17A or vehicle into Tlr9KO mice and assessing kidney function. IL-17A levels in both plasma and the peritoneal cavity and mRNA levels of IL-23 in the spleen were significantly higher in WT mice after CLP than in Tlr9KO mice. Bone marrow-derived DCs activated by TLR9 induced IL-23 and consequently promoted IL-17A production in γδT cells in vitro. Knockout of Il-17a improved survival, functional and morphological aspects of AKI, and splenic apoptosis after CLP. Exogenous IL-17A administration aggravated CLP-induced AKI attenuated by knockout of Tlr9. TLR9 in DCs mediated IL-17A production in γδT cells during sepsis and contributed to the development of septic AKI.

Pathogenic Role of an IL-23/γδT17/Neutrophil Axis in Coxsackievirus B3-Induced Pancreatitis

Coxsackievirus B is a common cause of viral myocarditis and pancreatitis. IL-17A is intensively involved in the pathogenesis of viral myocarditis. Whether IL-17A plays a role in Coxsackievirus B-induced pancreatitis, characterized by acinar cell destruction and immune infiltration, remains largely unknown. We found a significant, but transient, increase of IL-17A expression and γδT influx in the pancreas of C57BL/6J mice within 3 d following CVB3 infection. The pancreatic IL-17A was mainly produced by Vγ4 γδ T cells, to a lesser extent by CD4⁺ Th17 cells. IL-17A^-/- and TCRδ^-/- mice both reduced their susceptibility to CVB3 infection and pancreatitis severity when compared with the wild-type mice, without altering viral load. mAb depletion of Vγ4γδ T cells significantly improved mice survival and pancreatic pathology via decreasing Th17 expansion and neutrophil influx into the pancreas compared with isotype-treated mice. Transfer of Vγ4γδ T cells from wild-type, but not IL-17^-/-, mice reconstituted TCRδ^-/- mice to produce IL-17 and develop pancreatitis to the level of wild-type mice during CVB3 infection, indicating γδ T IL-17A is required for the onset of viral pancreatitis. IL-23 was robustly induced in the pancreas within the first day of infection. Administration of exogenous rIL-23 to mice increased CVB3 pancreatitis through in vivo expansion of IL-17⁺γδT17 cells at 12 h postinfection. Our findings reveal a key pathogenic role for early-activated γδT17 cells in viral pancreatitis via promoting neutrophil infiltration and Th17 induction. This IL-23/γδT17/neutrophil axis is critically involved in the onset of CVB3 pancreatitis and represents a potential treating target for the disease.

Immunotherapy in hepatocellular carcinoma: the complex interface between inflammation, fibrosis, and the immune response

Hepatocellular carcinoma (HCC) is the third leading cause of cancer deaths worldwide and confers a poor prognosis. Beyond standard systemic therapy with multikinase inhibitors, recent studies demonstrate the potential for robust and durable responses from immune checkpoint inhibition in subsets of HCC patients across disease etiologies. The majority of HCC arises in the context of chronic inflammation and from within a fibrotic liver, with many cases associated with hepatitis virus infections, toxins, and fatty liver disease. Many patients also have concomitant cirrhosis which is associated with both local and systemic immune deficiency. Furthermore, the liver is an immunologic organ in itself, which may enhance or suppress the immune response to cancer arising within it. Here, we explore the immunobiology of the liver from its native state to chronic inflammation, fibrosis, cirrhosis and then to cancer, and summarize how this unique microenvironment may affect the response to immunotherapy.

The protective and pathogenic roles of IL-17 in viral infections: friend or foe?

Viral infections cause substantial human morbidity and mortality, and are a significant health burden worldwide. Following a viral infection, the host may initiate complex antiviral immune responses to antagonize viral invasion and replication. However, proinflammatory antiviral immune responses pose a great threat to the host if not properly held in check. Interleukin (IL)-17 is a pleiotropic cytokine participating in a variety of physiological and pathophysiological conditions, including tissue integrity maintenance, cancer progression, autoimmune disease development and, more intriguingly, infectious diseases. Abundant evidence suggests that while IL-17 plays a crucial role in enhancing effective antiviral immune responses, it may also promote and exacerbate virus-induced illnesses. Accumulated experimental and clinical evidence has broadened our understanding of the seemingly paradoxical role of IL-17 in viral infections and suggests that IL-17-targeted immunotherapy may be a promising therapeutic option. Herein, we summarize current knowledge regarding the protective and pathogenic roles of IL-17 in viral infections, with emphasis on underlying mechanisms. The various and critical roles of IL-17 in viral infections necessitate the development of therapeutic strategies that are uniquely tailored to both the infectious agent and the infection environment.

IL-17 and IL-17-producing cells and liver diseases, with focus on autoimmune liver diseases

The pro-inflammatory cytokine interleukin(IL)-17 and IL-17-producing cells are important players in the pathogenesis of many autoimmune / inflammatory diseases. More recently, they have been associated with liver diseases. This review first describes the general knowledge on IL-17 and IL-17 producing cells. The second part describes the in vitro and in vivo effects of IL-17 on liver cells and the contribution of IL-17 producing cells to liver diseases. IL-17 induces immune cell infiltration and liver damage driving to hepatic inflammation and fibrosis and contributes to autoimmune liver diseases. The circulating levels of IL-17 and the frequency of IL-17-producing cells are elevated in a variety of acute and chronic liver diseases. The last part focuses on the effects of IL-17 deletion or neutralization in various murine models. Some of these observed beneficial effects suggest that targeting the IL-17 axis could be a new therapeutic strategy to prevent chronicity and progression of various liver diseases.

The role of the common gamma-chain family cytokines in γδ T cell-based anti-cancer immunotherapy

Cytokines of the common gamma-chain receptor family, comprising interleukin (IL)-2, IL-4, IL-7, IL-9, IL-15 and IL-21, are vital with respect to organizing and sustaining healthy immune cell functions. Supporting the anti-cancer immune response, these cytokines inspire great interest for their use as vaccine adjuvants and cancer immunotherapies. It is against this background that gamma delta (γδ) T cells, as special-force soldiers and natural contributors of the tumor immunosurveillance, also received a lot of attention the last decade. As γδ T cell-based cancer trials are coming of age, this present review focusses on the effects of the different cytokines of the common gamma-chain receptor family on γδ T cells with respect to boosting γδ T cells as a therapeutic target in cancer immunotherapy. This review also gathers data that IL-15 in particular exhibits key features for augmenting the anti-tumor activity of effector killer γδ T cells whilst overcoming the myriad of immune escape mechanisms used by cancer cells.

Ambiguous roles of innate lymphoid cells in chronic development of liver diseases

Innate lymphoid cells (ILCs) are defined as a distinct arm of innate immunity. According to their profile of secreted cytokines and lineage-specific transcriptional factors, ILCs can be categorized into the following three groups: group 1 ILCs (including natural killer (NK) cells and ILC1s) are dependent on T-bet and can produce interferon-γ; group 2 ILCs (ILC2s) are dependent on GATA3 and can produce type 2 cytokines, including interleukin (IL)-5 and IL-13; and, group 3 ILCs (including lymphoid tissue-like cells and ILC3s) are dependent on RORγt and can produce IL-22 and IL-17. Collaborative with adaptive immunity, ILCs are highly reactive innate effectors that promptly orchestrate immunity, inflammation and tissue repair. Dysregulation of ILCs might result in inflammatory disorders. Evidence regarding the function of intrahepatic ILCs is emerging from longitudinal studies of inflammatory liver diseases wherein they exert both physiological and pathological functions, including immune homeostasis, defenses and surveillance. Their overall effect on the liver depends on the balance of their proinflammatory and antiinflammatory populations, specific microenvironment and stages of immune responses. Here, we review the current data about ILCs in chronic liver disease progression, to reveal their roles in different stages as well as to discuss their therapeutic potency as intervention targets.

The IL7RA rs6897932 polymorphism is associated with progression of liver fibrosis in patients with chronic hepatitis C: Repeated measurements design

The polymorphisms at the α-chain of the IL-7 receptor (IL7RA) have been related to T-cell homeostasis and development and may contribute to immune system deregulation. In the present study, we analyzed the association between IL7RA polymorphisms and the progression of liver fibrosis in patients infected with HCV. We carried out a retrospective study with a design consisting of repeated measurements in 187 HCV-infected patients, to study the risk prediction of liver fibrosis progression using genetic factors. We genotyped the rs6897932, rs987106 and rs3194051 IL7RA polymorphisms using the Agena Bioscience's MassARRAY. Transient elastography was used to measure liver stiffness. The used cut-offs were: <7.1 kPa (F0-F1), 7.1-9.4 kPa (F2; significant fibrosis), 9.5-12.4 kPa (F3; advanced fibrosis), and ≥12.5 kPa (F4; cirrhosis). All HCV genotypes were analyzed. The median of follow-up time was 47.9 months. Baseline liver stiffness measurement (LSM) values did not show significant statistical differences for IL7RA genotypes (p>0.05). In univariate analysis, the rs6897932 T allele had a positive relationship with an increase in LSM (arithmetic mean ratio (AMR) = 1.21 (95%CI = 1.08; 1.36); p = 0.001), progression to advanced fibrosis (F≥3) (odds ratio (OR) = 2.51 (95%CI = 1.29; 4.88); p = 0.006) and progression to cirrhosis (F4) (OR = 2.71 (95%CI = 0.94; 5.03); p = 0.069). In multivariable analysis, the rs6897932 T allele was related to a higher increase of LSM values during follow-up (adjusted AMR = 1.27 (95%CI = 1.13; 1.42); p<0.001) and higher odds of progression to advanced fibrosis [adjusted OR = 4.46 (95%CI = 1.87; 10.62); p = 0.001], and progression to cirrhosis [adjusted OR = 3.92 (95%CI = 1.30; 11.77); p = 0.015]. Regarding IL7RA rs987106 and rs3194051 polymorphisms, we did not find significant results except for the relationship between IL7RA rs987106 and the increase in LSM values [adjusted OR = 1.12 (95%CI = 1.02; 1.23); p = 0.015]. The IL7RA rs6897932 polymorphism seems to be related to increased risk of liver fibrosis progression in HCV-infected patients. Thus, the rs6897932 polymorphism could be related to the physiopathology of CHC and might be used to successfully stratify the risk of CHC progression.

Type I IFN Receptor Signaling Controls IL7-Dependent Accumulation and Activity of Protumoral IL17A-Producing γδT Cells in Breast Cancer

The protumoral activity of γδT17 cells has recently emerged in a wide variety of solid malignancies, including breast cancer. These cells exert their detrimental functions by promoting tumor growth, angiogenesis, and subsequent metastasis development. However, the intratumoral factors that regulate the biology of γδT17cells within the tumor microenvironment are less well understood. Here, using two experimental models of breast cancer, we reinforced the concept that tumor-infiltrating γδT17 cells are endowed with protumoral functions, which promote tumor progression and metastasis development. More importantly, we demonstrated a critical role for type I IFN signaling in controlling the preferential accumulation in the tumor bed of a peculiar subset of γδT17 cells displaying a CD27^- CD3^bright phenotype (previously associated with the invariant Vγ6Vδ1⁺ TCR). Interestingly, this effect was indirect and partially relied on the IFNAR1-dependent control of IL7 secretion, a factor that triggers proliferation and activating functions of deleterious γδT17 cells. Our work therefore identifies a key role of the type I IFN/IL7 axis in the regulation of intratumoral γδT17-cell functions and in the development of primary breast tumor growth and metastasis.Significance: Tumor-derived IL7 can represent a therapeutic target to prevent accumulation of immune cells endowed with potent protumoral activities. Cancer Res; 78(1); 195-204. ©2017 AACR.

Role of interleukin (IL)-17 and T-helper (Th)17 cells in cancer

Interleukin-17 (IL-17), a pleiotropic proinflammatory cytokine, is reported to be significantly generated by a distinct subset of CD4⁺ T-cells, upgrading cancer-elicited inflammation and preventing cancer cells from immune surveillance. T-helper (Th)17 cells produced from naive CD4⁺ T cells have recently been renowned and generally accepted, gaining eminence in cancer studies and playing the effective role in context of cancer. Th17 cells are the main source of IL-17-secreting cells, It was found that other cell types produced this cytokine as well, including Group 3 innate lymphoid cells (ILC3), δγT cells, invariant natural killer T (iNKT) cells, lymphoid-tissue inducer (LTi)-like cells and Natural killer (NK) cells. Th17-associated cytokines give impetus to tumor progression, or inducing angiogenesis and metastasis. This review demonstrates an understanding on how the pro- or antitumor function of Th17 cells and IL-17 may change cancer progression, leading to the appearance of complex and pivotal biologic activities in tumor.

Gut-liver axis: gut microbiota in shaping hepatic innate immunity

Gut microbiota play an essential role in shaping immune cell responses. The liver was continuously exposed to metabolic products of intestinal commensal bacterial through portal vein and alteration of gut commensal bateria was always associated with increased risk of liver inflammation and autoimmune disease. Considered as a unique immunological organ, the liver is enriched with a large number of innate immune cells. Herein, we summarize the available literature of gut microbiota in shaping the response of hepatic innate immune cells including NKT cells, NK cells, γδ T cells and Kupffer cells during health and disease. Such knowledge might help to develop novel and innovative strategies for the prevention and therapy of innate immune cell-related liver disease.

The imbalance of Th17/Treg cells is involved in the progression of nonalcoholic fatty liver disease in mice

Background

Non-alcoholic fatty liver disease (NAFLD) is a common, chronic liver disease worldwide. Recent studies have shown that T helper (Th) 17 and regulatory T (Treg) cells play critical roles in various disorders of liver inflammation. Here, we explored the value of polyene phosphatidylcholine capsules (PPC) for regulating the imbalance of Th17/Treg cells in the pathogenesis of mice with NAFLD.

Methods

C57BL/6 mice were randomly divided into three groups as follows:normal diet (ND), high-fat diet (HF),and HF plus PPC(HF + PPC). The frequencies of splenic Th17 and Treg cells were measured by flow cytometry, and their related cytokines were analyzed by CBA and real-time PCR.

Results

At the end of 24 weeks, mice in the HF group had a higher frequency of intrahepatic Th17 cells,and a lower proportion of Treg cells compared with the ND group. The levels of Th17 cell-related cytokines (IL-6, IL-17 and IL-23) in serum and in liver tisse were increased,and the hepatic mRNA levels of RORγt, STAT3 and IL-6 were also increased. By contrast,the FoxP3 mRNA level was decreased in the HF group. Moreover, significant pathological and biochemical changes in the liver, as well as serum biochemical changes, were found in mice with NAFLD. Interestingly, following treatment with PPC, the levels of liver inflammation,frequencies of Th17/Treg cells and associated cytokines,and biochemical data were significantly altered.

Conclusion

These findings demonstrate a critical role for PPC in partially attenuating liver inflammatory responses in mice with NAFLD that involves the imbalance of Treg/Th17 cells and associated cytokines.

A tightly regulated IL-22 response maintains immune functions and homeostasis in systemic viral infection

Interleukin-22 (IL-22) plays an important role in host immunity and tissue homeostasis in infectious and inflammatory diseases. However, the function and regulation of IL-22 in viral infection remain largely unknown. Here, we report that viral infection triggered early IL-22 production from the liver and lymphoid organs. γδ T cells are the main immune cells to produce IL-22 in the liver, a process mediated by the IL-23/phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin complex 1 (mTORC1) signaling pathway. In the presence of IL-23, IL-22 production is independent of aryl hydrocarbon receptor (AhR) signaling. In acute and persistent viral infections, IL-22 deficiency resulted in thymic and splenic hypertrophy, while excessive IL-22 induced atrophy in these lymphoid organs. Moreover, IL-22 deficiency enhanced T cell responses to promote viral clearance, but increased IL-22 in vivo decreased T cell numbers and functions in the liver and lymphoid tissues. Together, our findings reveal a significant effect of the IL-23/PI3K/mTORC1 axis on regulating IL-22 production and also identify a novel role of IL-22 in controlling antiviral T cell responses in the non-lymphoid and lymphoid organs during acute and persistent viral infections.

Retinoic Acid Regulates Immune Responses by Promoting IL-22 and Modulating S100 Proteins in Viral Hepatitis

Although large amounts of vitamin A and its metabolite all-trans retinoic acid (RA) are stored in the liver, how RA regulates liver immune responses during viral infection remains unclear. In this study, we demonstrated that IL-22, mainly produced by hepatic γδ T cells, attenuated liver injury in adenovirus-infected mice. RA can promote γδ T cells to produce mTORC1-dependent IL-22 in the liver, but inhibits IFN-γ and IL-17. RA also affected the aptitude of T cell responses by modulating dendritic cell (DC) migration and costimulatory molecule expression. These results suggested that RA plays an immunomodulatory role in viral infection. Proteomics data revealed that RA downregulated S100 family protein expression in DCs, as well as NF-κB/ERK pathway activation in these cells. Furthermore, adoptive transfer of S100A4-repressed, virus-pulsed DCs into the hind foot of naive mice failed to prime T cell responses in draining lymph nodes. Our study has demonstrated a crucial role for RA in promoting IL-22 production and tempering DC function through downregulating S100 family proteins during viral hepatitis.

Betulin from Hedyotis hedyotidea ameliorates concanavalin A-induced and T cell-mediated autoimmune hepatitis in mice

Hedyotis hedyotidea has been used in traditional Chinese medicine for the treatment of autoimmune diseases. However, the mechanisms underlying for the effect remain unknown. We previously showed that, among 11 compounds extracted from H hedyotidea, betulin produced the strongest suppressive effect on T cell activation. Here, we examined the hepatoprotective effects of betulin against acute autoimmune hepatitis in mice and the mechanisms underlying the effects. Freshly isolated mouse splenocytes were stimulated with concanavalin A (Con A, 5 μg/mL) in the presence of betulin, the cell proliferation was assessed with CSFE-dilution assay. Mice were injected with betulin (10, 20 mg·kg^-1·d^-1, ip) for 3 d. One hour after the last injection, the mice were injected with Con A (15 mg/kg, iv) to induce acute hepatitis. Blood samples and liver tissues were harvested at 10 h after Con A injection, and serum transaminase levels and liver histopathology were detected; serum levels of proinflammatory cytokines, hepatic T lymphocyte ratios, and functional statuses of conventional T and NKT cells were also analyzed. Betulin (16 and 32 μmol/L) dose-dependently suppressed the proliferation of Con A-stimulated mouse splenocytes in vitro. In Con A-challenged mice, preinjection with betulin (20 mg·kg^-1·d^-1) significantly decreased the levels of proinflammatory cytokines IFN-γ, TNF-α and IL-6, and ameliorated liver injury. Furthermore, pretreatment with betulin (20 mg·kg^-1·d^-1) significantly inhibited the Con A-induced activation of NKT and conventional T cells, and decreased production of proinflammatory cytokines IFN-γ, TNF-α and IL-6 in these two cell populations. Betulin has immunomodulatory effect on overly activated conventional T and NKT cells and exerts hepatoprotective action in mouse autoimmune hepatitis. The findings provide evidence for the use of H hedyotidea and its constituent betulin in the treatment of autoimmune diseases.

Intrahepatic regulation of antiviral T cell responses at initial stages of viral infection

It is generally accepted that the appropriate boost of early immune response will control viral replications and limit the immune-mediated pathology in viral hepatitis. However, poor immunity results in viral persistence, chronic inflammation and finally liver cirrhosis and carcinoma. As a peripheral non-lymphoid organ of immune surveillance, the liver continually encounters hundreds of molecules from the blood, including nutrients, toxins and pathogens. In this way, the liver maintains immune tolerance under healthy conditions, but responds quickly to the hepatotropic pathogens during the early stages of an infection. Although our knowledge of liver cell compositions and functions has been improved significantly in recent years, the intrahepatic immune regulation of antiviral T cells at the initial stage is complex and not well elucidated. Here, we summarize the role of liver cell subpopulations in regulating antiviral T cell response at the initial stages of viral infection. A better understanding of early hepatic immune regulation will pave the way for the development of novel therapies and vaccine design for human viral hepatitis.

γδ T cells and the immune response to respiratory syncytial virus infection

γδ T cells are a subset of nonconventional T cells that play a critical role in bridging the innate and adaptive arms of the immune system. γδ T cells are particularly abundant in ruminant species and may constitute up to 60% of the circulating lymphocyte pool in young cattle. The frequency of circulating γδ T cells is highest in neonatal calves and declines as the animal ages, suggesting these cells may be particularly important in the immune system of the very young. Bovine respiratory syncytial virus (BRSV) is a significant cause of respiratory infection in calves, and is most severe in animals under one year of age. BRSV is also a significant factor in the development of bovine respiratory disease complex (BRDC), the leading cause of morbidity and mortality in feedlot cattle. Human respiratory syncytial virus (RSV) is closely related to BRSV and a leading cause of lower respiratory tract infection in infants and children worldwide. BRSV infection in calves shares striking similarities with RSV infection in human infants. To date, there have been few studies defining the role of γδ T cells in the immune response to BRSV or RSV infection in animals or humans, respectively. However, emerging evidence suggests that γδ T cells may play a critical role in the early recognition of infection and in shaping the development of the adaptive immune response through inflammatory chemokine and cytokine production. Further, while it is clear that γδ T cells accumulate in the lungs during BRSV and RSV infection, their role in protection vs. immunopathology remains unclear. This review will summarize what is currently known about the role of γδ T cells in the immune response to BRSV and BRDC in cattle, and where appropriate, draw parallels to the role of γδ T cells in the human response to RSV infection.

IL-33 promotes innate IFN-γ production and modulates dendritic cell response in LCMV-induced hepatitis in mice

Recent studies have revealed IL-33 as a key factor in promoting antiviral T-cell responses. However, it is less clear as to how IL-33 regulates innate immunity. In this study, we infected wild-type (WT) and IL-33(-/-) mice with lymphocytic choriomeningitis virus and demonstrated an essential role of infection-induced IL-33 expression for robust innate IFN-γ production in the liver. We first show that IL-33 deficiency resulted in a marked reduction in the number of IFN-γ(+) γδ T and NK cells, but an increase in that of IL-17(+) γδ T cells at 16 h postinfection. Recombinant IL-33 (rIL-33) treatment could reverse such deficiency via increasing IFN-γ-producing γδ T and NK cells, and inhibiting IL-17(+) γδ T cells. We also found that rIL-33-induced type 2 innate lymphoid cells were not involved in T-cell responses and liver injury, since the adoptive transfer of type 2 innate lymphoid cells neither affected the IFN-γ and TNF-α production in T cells, nor liver transferase levels in lymphocytic choriomeningitis virus infected mice. Interestingly, we found that while IL-33 was not required for costimulatory molecule expression, it was critical for DC proliferation and cytokine production. Together, this study highlights an essential role of IL-33 in regulating innate IFN-γ-production and DC function during viral hepatitis.

Association between IL7R polymorphisms and severe liver disease in HIV/HCV coinfected patients: a cross-sectional study

BACKGROUND

Interleukin-7 (IL-7) is a critical factor for T cell development and for maintaining and restoring homeostasis of mature T cells. Polymorphisms at α-chain of the IL-7 receptor (IL7R or CD127) gene are related to evolution of HIV-infection, but there are no data concerning the evolution of hepatitis C virus (HCV) infection. The aim of this study was to analyze the association between IL7R polymorphisms and severe liver disease in HCV/HIV coinfected patients.

METHODS

We performed a cross-sectional study in 220 naïve patients who underwent a liver biopsy. IL7R polymorphisms (rs6897932, rs987106 and rs3194051) were genotyped using the GoldenGate(®) assay. The outcome variables were: (a) liver biopsy: advanced fibrosis (F ≥ 3), severe activity grade (A3); (b) non-invasive indexes: advanced fibrosis (APRI ≥1.5 and FIB-4 ≥3.25). Logistic regression analysis was used to investigate the association between IL7R polymorphisms and outcome variables. This test gives the differences between groups and the odds ratio (OR) for liver disease.

RESULTS

Patients with rs6897932 CC genotype had higher likelihood of having A3 than patients with rs6897932 CT/TT (adjusted odds ratio (aOR) = 4.16; p = 0.026). Patients with rs987106 TT genotype had higher odds of having F ≥ 3 (aOR = 3.09; p = 0.009) than rs987106 AA/AT carriers. Finally, patients with rs3194051 AA genotype had higher odds of having severe liver fibrosis (F ≥ 3; APRI ≥1.5, and FIB4 ≥3.25) than patients with rs3194051 AG/GG genotype [aOR = 2.73 (p = 0.010); aOR = 2.52 (p = 0.029); and aOR = 4.01 (p = 0.027); respectively]. The CTA haplotype (comprised of rs6897932, rs987106, and rs3194051) carriers had higher odds of having F ≥ 3 (aOR = 1.85; p = 0.012), APRI ≥1.5 (aOR = 1.94; p = 0.023), and FIB4 ≥3.25 (aOR = 2.47; p = 0.024). Conversely, the CAG haplotype carriers had lower odds of having F ≥ 3 (aOR = 0.48; p = 0.011), APRI ≥1.5 (aOR = 0.48; p = 0.029), and FIB4 ≥3.25 (aOR = 0.29; p = 0.010).

CONCLUSIONS

The presence of IL7R polymorphisms seems to be related to severe liver disease in HIV/HCV coinfected patients, because patients with unfavorable IL7R genotypes (rs6897932 CC, rs987106 TT, and rs3194051AA) had a worse prognosis of CHC.

γδ T cells in infection and autoimmunity

Standing at the interface of innate and adaptive immune, γδ T cells play important pathophysiologic roles in infection, autoimmunity, and tumorigenesis. Recent studies indicate that γδ T cells could be categorized into IFN-γ(+) and IL-17(+) subsets, both of which possess select TCR usages, bear unique surface markers and require different cytokine signaling to maintain the homeostasis. In addition, as the major innate IL-17 producers, γδ T cells are increasingly appreciated for their involvement in various acute infections and injuries. This review will summarize the characteristics of IFN-γ(+) (γδ T-IFN-γ) and IL-17(+) γδ T cells (γδT17) and discuss their distinct pathogenic functions in different disease models.

Five Layers of Receptor Signaling in γδ T-Cell Differentiation and Activation

The contributions of γδ T-cells to immunity to infection or tumors critically depend on their activation and differentiation into effectors capable of secreting cytokines and killing infected or transformed cells. These processes are molecularly controlled by surface receptors that capture key extracellular cues and convey downstream intracellular signals that regulate γδ T-cell physiology. The understanding of how environmental signals are integrated by γδ T-cells is critical for their manipulation in clinical settings. Here, we discuss how different classes of surface receptors impact on human and murine γδ T-cell differentiation, activation, and expansion. In particular, we review the role of five receptor types: the T-cell receptor (TCR), costimulatory receptors, cytokine receptors, NK receptors, and inhibitory receptors. Some of the key players are the costimulatory receptors CD27 and CD28, which differentially impact on pro-inflammatory subsets of γδ T-cells; the cytokine receptors IL-2R, IL-7R, and IL-15R, which drive functional differentiation and expansion of γδ T-cells; the NK receptor NKG2D and its contribution to γδ T-cell cytotoxicity; and the inhibitory receptors PD-1 and BTLA that control γδ T-cell homeostasis. We discuss these and other receptors in the context of a five-step model of receptor signaling in γδ T-cell differentiation and activation, and discuss its implications for the manipulation of γδ T-cells in immunotherapy.

Retention and tolerance of autoreactive CD4(+) recent thymic emigrants in the liver

Mechanisms of peripheral tolerance play a critical role in preventing T cells that escape from negative selection in the thymus from initiating autoimmune reactions. To investigate the site of peripheral tolerance induction, we examined migration and activation of recent thymic emigrants (RTEs) in liver, spleen, lymph node and peripheral blood. We show that a fraction of RTE precursors were retained in the liver independent of the secondary lymphoid organs. Compared to RTEs from the lymph nodes, RTEs from the liver proliferated more and many exhibited an activated phenotype with the capability of producing IL-10 upon activation. Liver RTEs also responded poorly to interleukin (IL)-7 and were more prone to apoptosis. Following transfer into RAG(-/-) recipients, liver RTEs induced more severe inflammation and T cell infiltration in the lung and colon. The extrathymic expression of MHC and Aire is required for the acquisition of tolerogenic phenotype of newly generated thymic emigrants in the liver. These results suggest that the liver is the first checkpoint in the periphery to filter, retain, and enforce tolerance to autoreactive CD4(+) thymic emigrants that escape from negative selection.

Mixing Signals: Molecular Turn Ons and Turn Offs for Innate γδ T-Cells

Lymphocytes of the gamma delta (γδ) T-cell lineage are evolutionary conserved and although they express rearranged antigen-specific receptors, a large proportion respond as innate effectors. γδ T-cells are poised to combat infection by responding rapidly to cytokine stimuli similar to innate lymphoid cells. This potential to initiate strong inflammatory responses necessitates that inhibitory signals are balanced with activation signals. Here, we discuss some of the key mechanisms that regulate the development, activation, and inhibition of innate γδ T-cells in light of recent evidence that the inhibitory immunoglobulin-superfamily member B and T lymphocyte attenuator restricts their differentiation and effector function.

γδ T Cell-Mediated Immune Responses in Disease and Therapy

The role of γδ T cells in immunotherapy has gained specific importance in the recent years because of their prominent function involving directly or indirectly in the rehabilitation of the diseases. γδ T cells represent a minor population of T cells that express a distinct T cell receptor (TCR) composed of γδ chains instead of αβ chains. Unlike αβ T cells, γδ T cells display a restricted TCR repertoire and recognize mostly unknown non-peptide antigens. γδ T cells act as a link between innate and adaptive immunity, because they lack precise major histocompatibility complex (MHC) restriction and seize the ability to recognize ligands that are generated during affliction. Skin epidermal γδ T cells recognize antigen expressed by damaged or stressed keratinocytes and play an indispensable role in tissue homeostasis and repair through secretion of distinct growth factors. γδ T cell based immunotherapy strategies possess great prominence in the treatment because of the property of their MHC-independent cytotoxicity, copious amount of cytokine release, and a immediate response in infections. Understanding the role of γδ T cells in pathogenic infections, wound healing, autoimmune diseases, and cancer might provide knowledge for the successful treatment of these diseases using γδ T cell based immunotherapy. Enhancing the human Vγ9Vδ2 T cells functions by administration of aminobisphosphonates like zoledronate, pamidronate, and bromohydrin pyrophosphate along with cytokines and monoclonal antibodies shows a hopeful approach for treatment of tumors and infections. The current review summarizes the role of γδ T cells in various human diseases and immunotherapeutic approaches using γδ T cells.

Impaired gamma delta T cell-derived IL-17A and inflammasome activation during early respiratory syncytial virus infection in infants

Respiratory syncytial virus (RSV) infection remains a significant global health burden disproportionately affecting infants and leading to long-term lung disease. IL-17A has been shown to be involved in regulating viral and allergic lung inflammatory responses, which has led to a more recent interest in its role in RSV infection. Using a neonatal mouse model of RSV, we demonstrate that neonates fail to develop IL-17A responses compared to adult mice; the main immediate IL-17A contributor in adults were γδ T cells. Antibody neutralization of IL-17A in adult mice caused increased lung inflammation and airway mucus from RSV, while exogenous IL-17A administration to RSV-infected neonates caused decreased inflammation but no change in airway mucus. We also observed a lack of pro-inflammatory cytokine production (IL-1β, IL-6) from infected neonates. Using human cord blood mononuclear cells (CBMCs) and adult peripheral blood mononuclear cells (PBMCs), we compared inflammasome activation by direct retinoic acid-inducible gene I (RIG-I) agonism; CBMCs failed to induce pro-inflammatory cytokines or IL-17A⁺ γδ T cells compared to PBMCs. Our results indicate that RSV disease severity is in part mediated by a lack of inflammasome activation and IL-17A production in neonates.

Association between IL7RA polymorphisms and the successful therapy against HCV in HIV/HCV-coinfected patients

Interleukin-7 (IL-7) is a critical factor in maintaining or inducing effective antiviral CD4+ and CD8+ T-cell responses. The aim of this study was to examine the association of interleukin-7 receptor-α (IL7RA) polymorphisms with a sustained virologic response (SVR) after hepatitis C virus (HCV) therapy with pegylated interferon-alpha plus ribavirin (pegIFNα/ribavirin) in 177 human immunodeficiency virus (HIV)/HCV-coinfected patients. We performed a retrospective study in 177 naïve patients who started HCV treatment. The IL7RA rs6897932, rs987106, and rs3194051 polymorphisms were genotyped by the GoldenGate® assay. An SVR was defined as undetectable HCV viral load through 24 weeks after the end of HCV treatment. The highest SVR rate was found in patients with the rs6897932 CC (p = 0.029) and rs3194051 GG (p = 0.002) genotypes, and HCV genotypes 2/3 (GT2/3) infected patients with the rs987106 AA genotype (p = 0.048). Additionally, carriers of the rs3194051 GG genotype had a higher likelihood of achieving an SVR [adjusted odds ratio (aOR) = 5.32; 95 % confidence interval (CI) = 1.07-26.94; p = 0.040] than patients with the rs3194051 AA/AG genotype, while rs6897932 CC (aOR = 0.63; p = 0.205) and rs987106 AA (aOR = 0.60; p = 0.213) were not significant. Moreover, three major haplotypes were found: 46.6 % for CTA, 32.4 % for CAG, and 20.7 % for TAA haplotypes. Patients infected with GT2/3 and carriers of the CTA haplotype had lower odds of achieving an SVR (aOR = 0.08; p = 0.004) and the CAG haplotype (favorable alleles) had higher odds of achieving an SVR than other haplotypes (aOR = 21.96; p < 0.001). IL7RA polymorphisms seem to play a significant role in the virological response to pegIFNα/ribavirin therapy in HIV/HCV-coinfected patients, in particular among patients infected with HCV GT2/3.

γδ T cells as a major source of IL-17 production during age-dependent RPE degeneration

PURPOSE

Chronic inflammation is a key factor contributing to the progression of age-related macular degeneration (AMD). The goals of the current study were to develop an improved mouse model with retinal pathologic features similar to those of AMD and to characterize the immunoreactive cells in the outer retina and choroid during degeneration of the retinal pigment epithelium (RPE).

METHODS

Mice deficient in nuclear erythroid 2-related factor 2 (Nrf2) at 12 months of age were fed a high-fat, cholesterol-rich diet for up to 16 weeks. Ocular phenotype was monitored by optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) in live animals, and was further validated by retinal histopathology. Immunofluorescence staining of either cryosections or RPE flat mounts was used to define immunoreactive cells. Flow cytometry analyses were further performed to define the subsets of intraocular T lymphocytes.

RESULTS

After 16 weeks on a high-fat (HF) diet, 58% of the eyes from Nrf2-/- mice had progression of retinal lesions. Major histocompatibility complex class II (MHC II)-positive microglia, FoxP3+ regulatory T cells (Tregs), and CD3+ IL-17-producing T cells were detected in either the retina or sub-RPE space. Flow cytometry analyses further revealed that most of the IL-17-producing cells were CD3+ CD4- TCRγδ+ cells.

CONCLUSIONS

The results suggest that the T cell-mediated immune responses played important roles in controlling the progression of AMD-like phenotype in Nrf2-deficient mice.

Type 1 interferon-induced IL-7 maintains CD8+ T-cell responses and homeostasis by suppressing PD-1 expression in viral hepatitis

Type 1 interferon (IFN-I) promotes antigen-presenting cell maturation and was recently shown to induce hepatic IL-7 production during infection. Herein, we further explored the underlying mechanisms used by IFN-I to orchestrate antiviral immune responses in the liver. Acute viral hepatitis was induced by i.v. injection of adenovirus (Ad) in IFN-α receptor knockout (IFNAR(-/-)) and control mice. To disrupt signaling, monoclonal antibodies (mAbs) against IL-7 receptor alpha (IL-7Rα) or PD-L1 were i.p. injected. We found that CD8(+) T cells in IFNAR(-/-) mice were less effective than those in control mice. The reduced T-cell function was accompanied by increased levels of PD-1 expression, apoptosis and decreased IFN-γ production. The lack of IFN-I signaling also impaired the expression of accessory molecules in both intrahepatic dendritic cell (DCs) and hepatocytes. PD-L1 was comparably and highly expressed on hepatocytes in both IFNAR(-/-) and control mice. Injection of PD-L1-specific mAb in IFNAR(-/-) mice reversed the compromised immune responses in the liver. Further investigation showed that hepatic IL-7 elevation was less pronounced in IFNAR(-/-) mice compared to the controls. A treatment with recombinant IL-7 suppressed PD-1 expression on CD8(+) T cells in vitro. Accordingly, blocking IL-7R signaling in vivo resulted in increased PD-1 expression on CD8(+) T cells in Ad-infected mice. Collectively, the results suggest that IFN-I-induced hepatic IL-7 production maintains antiviral CD8(+) T-cell responses and homeostasis by suppressing PD-1 expression in acute viral hepatitis.

Immunological basis of stem cell therapy in liver diseases

Unbalanced immune cell populations or immune cell infiltration of the liver can disrupt the immune-privileged state of the liver, resulting in liver injury or fibrosis. Therefore, the treatment for liver diseases involves not only hepatic regeneration but also immunological regulation. Recent studies demonstrated that stem cells, especially mesenchymal stem cells, have the capacity for not only hepatic differentiation but also immunomodulation. In this respect, stem cell therapy could be a realistic aim for liver diseases by modulating the liver regenerative processes and down-regulating immune-mediated liver damage. In this review, we discuss in detail the importance of immune cells in liver injury and repair; the mechanism by which stem cells demonstrate an immune-tolerant phenotype that can be used for allogeneic transplantation; the effect of stem cell transplantation on immune-mediated diseases, especially liver diseases; and the mechanism by which stem cells improve the hepatic microenvironment.

Endogenous interleukin (IL)-17A promotes pristane-induced systemic autoimmunity and lupus nephritis induced by pristane

Interleukin (IL)-17A is increased both in serum and in kidney biopsies from patients with lupus nephritis, but direct evidence of pathogenicity is less well established. Administration of pristane to genetically intact mice results in the production of autoantibodies and proliferative glomerulonephritis, resembling human lupus nephritis. These studies sought to define the role of IL-17A in experimental lupus induced by pristane administration. Pristane was administered to wild-type (WT) and IL-17A(-/-) mice. Local and systemic immune responses were assessed after 6 days and 8 weeks, and autoimmunity, glomerular inflammation and renal injury were measured at 7 months. IL-17A production increased significantly 6 days after pristane injection, with innate immune cells, neutrophils (Ly6G(+)) and macrophages (F4/80(+)) being the predominant source of IL-17A. After 8 weeks, while systemic IL-17A was still readily detected in WT mice, the levels of proinflammatory cytokines, interferon (IFN)-γ and tumour necrosis factor (TNF) were diminished in the absence of endogenous IL-17A. Seven months after pristane treatment humoral autoimmunity was diminished in the absence of IL-17A, with decreased levels of immunoglobulin (Ig)G and anti-dsDNA antibodies. Renal inflammation and injury was less in the absence of IL-17A. Compared to WT mice, glomerular IgG, complement deposition, glomerular CD4(+) T cells and intrarenal expression of T helper type 1 (Th1)-associated proinflammatory mediators were decreased in IL-17A(-/-) mice. WT mice developed progressive proteinuria, but functional and histological renal injury was attenuated in the absence of IL-17A. Therefore, IL-17A is required for the full development of autoimmunity and lupus nephritis in experimental SLE, and early in the development of autoimmunity, innate immune cells produce IL-17A.

Role of gamma-delta T cells in liver inflammation and fibrosis

Conventional adaptive T cell responses contribute to liver inflammation and fibrogenesis, especially in chronic viral infections and autoimmune hepatitis. However, the role of unconventional gamma-delta (γδ) T cells in liver diseases is less clear. In the past two decades, accumulating evidence revealed that γδ T cell numbers remarkably increase in the liver upon various inflammatory conditions in mice and humans. More recent studies demonstrated that the functional effect of γδ T cells on liver disease progression depends on the subsets involved, which can be identified by the expression of distinct T cell receptor chains and of specific cytokines. Fascinatingly, γδ T cells may have protective as well as pathogenic functions in liver diseases. Interferon γ-producing γδ T cells, for example, induce apoptosis in hepatocytes but also in hepatic tumor cells; while interleukin-17-expressing γδ T cells can downregulate pathogenic effector functions of other immune cells and can promote apoptosis of fibrogenic stellate cells. However, the results obtained in human liver disease as well as murine models are not fully conclusive at present, and the effects of γδ T cells on the outcome of liver disease might vary dependent on etiology and stage of disease. Further definitions of the γδ T cell subsets involved in acute and chronic liver inflammation, as well as their effector cytokines might uncover whether interference with γδ T cells could be a useful target for the treatment of liver disease.

IL-17 contributes to neutrophil recruitment but not to control of viral replication during acute mouse adenovirus type 1 respiratory infection

IL-17-producing CD4(+) helper T cells (Th17 cells) promote inflammatory responses to many pathogens. We used mouse adenovirus type 1 (MAV-1) to determine contributions of IL-17 to adenovirus pathogenesis. MAV-1 infection of C57BL/6 mice upregulated lung expression of IL-17 and the Th17-associated factors IL-23 and RORγt. Only CD4(+)T cells were associated with virus-specific IL-17 production. Fewer neutrophils were recruited to airways of IL-17(-/-) mice following MAV-1 infection, but there were no other differences in pulmonary inflammation between IL-17(+/+) and IL-17(-/-) mice. Mice depleted of neutrophils using anti-Gr-1 antibody had greater lung viral loads than controls. Despite impaired neutrophil recruitment, there were no differences between IL-17(+/+) and IL-17(-/-) mice in peak lung viral loads, clearance of virus from the lungs, or establishment of protective immunity. We demonstrate robust Th17 responses during MAV-1 respiratory infection, but these responses are not essential for control of virus infection or for virus-induced pulmonary inflammation.

Intrahepatic innate lymphoid cells secrete IL-17A and IL-17F that are crucial for T cell priming in viral infection

Intrahepatic cell-derived, early IL-17 is important for activating APCs in viral infection; however, the source and regulation of this IL-17 surge in the liver microenvironment are not well defined. In this article, we present evidence for a significant expansion of IL-17A/F-producing cells in mouse liver within 24 h of adenovirus infection. In addition to γδ T cells, a subset of IL-17A/F(+) cells expressed no myeloid or lymphoid lineage markers. Instead, they expressed high levels of stem cell markers, IL-7R and RORγt, consistent with the newly described innate lymphoid cells (ILCs). Based on their unique surface markers and cytokine profiles, these cells were confirmed as group 3 ILCs. In addition to adenovirus infection, group 3 ILCs were also found in mouse liver within 24 h of lymphocytic choriomeningitis virus infection. They contributed significantly to the establishment of the early cytokine milieu in virus-infected liver. Functional studies with mice deficient of IL-17R, IL-17A, and IL-17F further revealed that IL-17 signaling was critical for priming T cell responses in viral hepatitis. IL-17A repressed IL-17F secretion in vitro and in vivo; IL-17F(+) intrahepatic cells expanded more vigorously in IL-17A knockout animals, permitting efficient Ag presentation and T cell function. However, IL-17F neither inhibited IL-17A in vitro nor regulated its secretion in vivo. Together, this study has demonstrated the importance of a unique intrahepatic subpopulation and subsequent IL-17A/F regulation at initial stages of viral infection in the liver. These results have important implications for anticytokine biologic therapy and vaccine development.

Liver-brain interactions in inflammatory liver diseases: implications for fatigue and mood disorders

Chronic inflammatory liver diseases are often accompanied by behavior alterations including fatigue, mood disorders, cognitive dysfunction and sleep disturbances. These altered behaviors can adversely affect patient quality of life. The communication pathways between the inflamed liver and the brain that mediate changes in central neural activity leading to behavior alterations during liver inflammation are poorly understood. Neural and humoral communication pathways have been most commonly implicated as driving peripheral inflammation to brain signaling. Classically, the cytokines TNFα, IL-1β and IL-6 have received the greatest scientific attention as potential mediators of this communication pathway. In mice with liver inflammation we have identified a novel immune-mediated liver-to-brain communication pathway whereby CCR2(+) monocytes found within the peripheral circulation transmigrate into the brain parenchyma in response to MCP-1/CCL2 expressing activated microglia. Inhibition of cerebral monocyte infiltration in these mice significantly improved liver inflammation associated sickness behaviors. Importantly, in recent work we have found that at an earlier time point, when cerebral monocyte infiltration is not evident in mice with liver inflammation, increased monocyte:cerebral endothelial cell adhesive interactions are observed using intravital microscopy of the brain. These monocyte:cerebral endothelial cell adhesive interactions are P-selectin mediated, and inhibition of these interactions attenuated microglial activation and sickness behavior development. Delineating the pathways that the periphery uses to communicate with the brain during inflammatory liver diseases, and the central neurotransmitter systems that are altered through these communication pathways (e.g., serotonin, corticotrophin releasing hormone) to give rise to liver inflammation-associated sickness behaviors, will allow for the identification of novel therapeutic targets to decrease the burden of debilitating symptoms in these patients.

Therapeutic potential of interleukin-17 in inflammation and autoimmune diseases

INTRODUCTION

Interleukin-17 (IL-17) is a proinflammatory cytokine that mainly produced by T helper 17 (Th17) cells. In this article, we discussed the role of IL-17 in inflammation and autoimmune diseases, and the therapeutic strategies targeting IL-17.

AREAS COVERED

In this article, we discussed the proinflammatory cytokine IL-17 and IL-17 receptors signals, and their regulation. IL-17 expression was abnormal in the bacterium, virus and fungus infection, and its higher level caused the tissue inflammation. IL-17 was involved in the pathological process of autoimmune diseases, such as systemic sclerosis, rheumatoid arthritis, ankylosing spondylitis and systemic lupus erythematosus, and IL-17 has been put as a therapeutic target in the clinic.

EXPERT OPINION

IL-17/IL-17R signals and their application in inflammation process still need to be explored. Therapeutic strategies targeting IL-17 in autoimmune diseases ameliorated the inadequate response to anti-TNF-α therapy.

CD30 is required for activation of a unique subset of interleukin-17A-producing γδ T cells in innate immunity against Mycobacterium bovis Bacillus Calmette-Guerin infection

Interleukin-17A (IL-17A)-producing γδ T cells are known to be activated following Mycobacterium bovis bacillus Calmette-Guérin (BCG) infection. Here, we show that CD30, a member of the tumor necrosis factor (TNF) receptor superfamily, is important for activation of IL-17A-producing γδ T cells after BCG infection. Vγ1(-) Vγ4(-) γδ T cells preferentially expressing Vγ6/Vδ1 genes were identified as the major source of IL-17A in the peritoneal cavity during the early stage of BCG infection. The number of IL-17A-producing Vγ1(-) Vγ4(-) γδ T cells bearing Vγ6 increased in peritoneal exudate cells (PEC) of wild-type (WT) mice but not in those of CD30 knockout (KO) mice in response to BCG infection. Consistently, CD30 ligand (CD30L) or CD30 expression, predominantly by Vγ1(-) Vγ4(-) γδ T cells, was rapidly upregulated after BCG infection. Inhibition of CD30L/CD30 signaling by in vivo administration of a soluble CD30 and immunoglobulin fusion protein (CD30-Ig) severely impaired activation of IL-17A-producing Vγ1(-) Vγ4(-) γδ T cells in WT mice, while stimulating CD30L/CD30 signaling by in vivo administration of agonistic anti-CD30 monoclonal antibody (MAb) restored IL-17A production by Vγ1(-) Vγ4(-) γδ T cells in CD30L KO mice after BCG infection. These results suggest that CD30 signaling plays an important role in the activation of IL-17A-producing Vγ1(-) Vγ4(-) γδ T cells bearing Vγ6 at an early stage of BCG infection.