Simultaneous expression of th1 cytokines and IL-4 confers severe characteristics to type I autoimmune hepatitis in children

Natural Killer T (NKT) Cells in Autoimmune Hepatitis: Current Evidence from Basic and Clinical Research

Natural killer T (NKT) cells are unconventional T cells that are activated by glycolipid antigens. They can produce a variety of inflammatory and regulatory cytokines and, therefore, modulate multiple aspects of the immune response in different pathological settings, including autoimmunity. NKT cells have also been implicated in the immunopathogenesis of autoimmune hepatitis, and in this review we summarize and analyze the main studies investigating the involvement and/or homeostasis of NKT cells in this disease. In detail, the evidence from both basic and clinical research has been specifically analyzed. Even though the experimental murine models supported a relevant role of NKT cells in immune-mediated hepatic injury, very few studies specifically investigated NKT cell homeostasis in patients with autoimmune hepatitis; however, these initial studies reported some alterations of NKT cells in these patients, which may also correlate with the disease activity to some extent. Further clinical studies are needed to investigate the potential role and use of NKT cell analysis as a disease marker of clinical relevance, and to better understand the precise cellular and molecular mechanisms by which NKT cells contribute to the pathogenesis of autoimmune hepatitis.

Pathogenesis of Autoimmune Hepatitis-Cellular and Molecular Mechanisms

Pediatric autoimmune liver disorders include autoimmune hepatitis (AIH), autoimmune sclerosing cholangitis (ASC), and de novo AIH after liver transplantation. AIH is an idiopathic disease characterized by immune-mediated hepatocyte injury associated with the destruction of liver cells, causing inflammation, liver failure, and fibrosis, typically associated with autoantibodies. The etiology of AIH is not entirely unraveled, but evidence supports an intricate interaction among genetic variants, environmental factors, and epigenetic modifications. The pathogenesis of AIH comprises the interaction between specific genetic traits and molecular mimicry for disease development, impaired immunoregulatory mechanisms, including CD4+ T cell population and Treg cells, alongside other contributory roles played by CD8+ cytotoxicity and autoantibody production by B cells. These findings delineate an intricate pathway that includes gene to gene and gene to environment interactions with various drugs, viral infections, and the complex microbiome. Epigenetics emphasizes gene expression through hereditary and reversible modifications of the chromatin architecture without interfering with the DNA sequence. These alterations comprise DNA methylation, histone transformations, and non-coding small (miRNA) and long (lncRNA) RNA transcriptions. The current first-line therapy comprises prednisolone plus azathioprine to induce clinical and biochemical remission. Further understanding of the cellular and molecular mechanisms encountered in AIH may depict their impact on clinical aspects, detect biomarkers, and guide toward novel, effective, and better-targeted therapies with fewer side effects.

Functional heterogeneity of CD4+ T cells in liver inflammation

CD4⁺ T cells play an essential role in orchestrating adequate immunity, but their overactivity has been associated with the development of immune-mediated inflammatory diseases, including liver inflammatory diseases. These cells can be subclassified according to their maturation stage, cytokine profile, and pro or anti-inflammatory functions, i.e., functional heterogeneity. In this review, we summarize what has been discovered so far regarding the role of the different CD4⁺ T cell polarization states in the progression of two prominent and still different liver inflammatory diseases: non-alcoholic steatohepatitis (NASH) and autoimmune hepatitis (AIH). Finally, the potential of CD4⁺ T cells as a therapeutic target in both NASH and AIH is discussed.

Mechanisms of autoimmune hepatitis

PURPOSE OF REVIEW

Autoimmune hepatitis (AIH) is a chronic disease characterized by a lymphocyte infiltrate in the liver. For decades, nonspecific immunosuppression has been used to limit chronic liver inflammation. The high risk of relapse, the treatments side effects, and the significant number of refractory patients are the main clinical issues that require efforts to understand AIH immune mechanisms.

RECENT FINDINGS

The balance between regulatory CD4 T cells, known to control autoimmunity, and effector CD4 T cells, that recognize liver self-antigens and mediate the liver inflammation, appears central in AIH immune mechanisms. Recent advances in the identification of pathogenic auto-reactive CD4 T cells, and of new mechanisms of immune regulatory defects in AIH patients, give new insights into the pathophysiology of this disease.

SUMMARY

In this review, we propose an overview of the central role of CD4 T cells (both regulatory and pathogenic) in mechanisms of AIH, with a focus on recent advances regarding defective regulatory mechanisms and immune profile of auto-reactive CD4 T cells. These findings may have implication for the orientation of new therapeutic strategies to treat AIH, such as regulatory T-cell infusion or targeting B cells and cytokines released by pathogenic CD4 T cells.

Innate lymphocytes: pathogenesis and therapeutic targets of liver diseases and cancer

The liver is a lymphoid organ with unique immunological properties, particularly, its predominant innate immune system. The balance between immune tolerance and immune activity is critical to liver physiological functions and is responsible for the sensitivity of this organ to numerous diseases, including hepatotropic virus infection, alcoholic liver disease, nonalcoholic fatty liver disease, autoimmune liver disease, and liver cancer, which are major health problems globally. In the past decade, with the discovery of liver-resident natural killer cells, the importance of innate lymphocytes with tissue residency has gradually become the focus of research. In this review, we address the current knowledge regarding hepatic innate lymphocytes with unique characteristics, including NK cells, ILC1/2/3s, NKT cells, γδ T cells, and MAIT cells, and their potential roles in liver homeostasis maintenance and the progression of liver diseases and cancer. A better understanding of the immunopathogenesis of hepatic innate lymphocytes will be helpful for proposing effective treatments for liver diseases and cancer.

Inflammatory Phenotype of Intrahepatic Sulfatide-Reactive Type II NKT Cells in Humans With Autoimmune Hepatitis

Background: Natural Killer T (NKT) cells are CD1d-restricted innate-like T cells that can rapidly release stored cytokines upon recognition of lipid antigens. In mice, type I NKT cells seem to promote liver inflammation, whereas type II NKT cells seem to restrict hepatitis. Here, we aimed at characterizing the role of human type I and type II NKT in patients with autoimmune hepatitis (AIH).

Methods: NKT cells were analyzed by flow cytometry in peripheral blood and liver of AIH patients and control groups. α-galactosylceramide-loaded or sulfatide-loaded tetramers were used to detect type I or II NKT cells, respectively. Hepatic CD1d was stained by in situ-hybridization of liver biopsies.

Results and Conclusions: Type II NKT cells were more prevalent in human peripheral blood and liver than type I NKT cells. In AIH patients, the frequency of sulfatide-reactive type II NKT cells was significantly increased in peripheral blood (0.11% of peripheral blood leukocytes) and liver (3.78% of intrahepatic leukocytes) compared to healthy individuals (0.05% and 1.82%) and patients with drug-induced liver injury (0.06% and 2.03%; p < 0.05). Intrahepatic type II NKT cells of AIH patients had a different cytokine profile than healthy subjects with an increased frequency of TNFα (77.8% vs. 59.1%, p < 0.05), decreased IFNγ (32.7% vs. 63.0%, p < 0.05) and a complete lack of IL-4 expressing cells (0% vs. 2.1%, p < 0.05). T cells in portal tracts expressed significantly more CD1d-RNA in AIH livers compared to controls. This study supports that in contrast to their assumed protective role in mice, human intrahepatic, sulfatide-reactive type II NKT cells displayed a proinflammatory cytokine profile in patients with AIH. Infiltrating T cells in portal areas of AIH patients overexpressed CD1d and could thereby activate type II NKT cells.

Cellular and Molecular Mechanisms of Autoimmune Hepatitis

Autoimmune hepatitis is an uncommon idiopathic syndrome of immune-mediated destruction of hepatocytes, typically associated with autoantibodies. The disease etiology is incompletely understood but includes a clear association with human leukocyte antigen (HLA) variants and other non-HLA gene variants, female sex, and the environment. Pathologically, there is a CD4+ T cell-rich lymphocytic inflammatory infiltrate with variable hepatocyte necrosis and subsequent hepatic fibrosis. Attempts to understand pathogenesis are informed by several monogenetic syndromes that may include autoimmune liver injury, by several drug and environmental agents that have been identified as triggers in a minority of cases, by human studies that point toward a central role for CD4+ effector and regulatory T cells, and by animal models of the disease. Nonspecific immunosuppression is the current standard therapy. Further understanding of the disease's cellular and molecular mechanisms may assist in the design of better-targeted therapies, aid the limitation of adverse effects from therapy, and inform individualized risk assessment and prognostication.

Immune Alterations in Patients With Type 1 Autoimmune Hepatitis Persist Upon Standard Immunosuppressive Treatment

Autoimmune hepatitis (AIH) is a rare disease characterized by an immune attack of the liver. This study consists of a comprehensive analysis of immune alterations related to AIH at diagnosis, and during remission phase under treatment. A total of 37 major lymphocyte populations were analyzed from the peripheral blood of new‐onset AIH patients (AIHn; n = 14), AIH patients with controlled disease (n = 11), and healthy subjects (n = 14). Liver biopsy analyses were performed to complete the blood phenotypic analysis. Four blood lymphocyte populations were significantly altered in AIHn patients at diagnosis compared with healthy subjects. Levels of mucosal‐associated invariant T cells (MAIT), Type 1/Type 17 helper (Th1/ Th17) cells, clusters of differentiation (CD4) T cells, and invariant natural killer T cells were decreased, whereas MAIT granzyme B+ (GrB) cells were increased. A trend toward an increase of CD8+CD161+GrB+ cells was also observed. These alterations were not restored with standard immunosuppressive treatments. In the liver of AIHn patients, CD4, forkhead box P3 (Foxp3), and MAIT cell markers were enriched in the portal tract, and CD8, CD161, and GrB markers were enriched in the hepatic lobule. During remission, the hepatic lobule was clear of infiltrating T cells, but residual CD4 and MAIT cells were found in the portal tract, where Foxp3 was decreased, as previously described. In vitro, MAIT cells were functionally altered in AIH patients. Ex vivo MAIT cell activity (GrB) was linked to severe fibrosis. Conclusion: Our work proposes a global view of the lymphocyte alterations from diagnosis to remission phase in AIH patients. The absence of blood immune homeostasis restoration and the persistence of a CD4 infiltrate in the liver under standard immunosuppression could form the basis of the high risk of relapse observed in AIH. (Hepatology Communications 2018; 00:000‐000)

Association of interleukin (IL)-4 variable number of tandem repeats (VNTRs) and IL-4-590 promoter polymorphisms with susceptibility to pediatric autoimmune hepatitis type 1

OBJECTIVE

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease mediated by an autoimmune reaction to hepatocytes, the present study aimed to assess the possible associations between interleukin-4 (IL-4) variable number of tandem repeats (VNTRs) and IL-4-590 promoter polymorphisms and susceptibility to autoimmune hepatitis type 1 in children.

SUBJECTS AND METHODS

The study was performed on 101 children diagnosed with AIH and 104 apparently healthy, age and sex-matched control children, diagnosis of AIH was based on the simplified score for the diagnosis of AIH. Genotyping for the IL-4 VNTR and IL-4-590 were performed using PCR-RFLP.

RESULTS

The distribution of genotype frequencies of IL-4 gene intron 3 VNTR polymorphism were not significantly different between AIH patients and controls for 3R/2R and 2R/2R genotypes, while the 2R allele distribution was significantly higher among AIH patients than the control group. The frequency of IL-4-590 single nucleotide polymorphism (SNP) CT and TT genotypes was statistically higher among AIH patients than controls.

CONCLUSION

This study revealed the presence of an association between IL-4 -590 TT genotype and T alleles with increased AIH risk in pediatric patients, also assess its severity as they were detected with Child Plugh scores B and C.

IL4 gene polymorphisms in Iranian patients with autoimmune hepatitis

BACKGROUND

Autoimmune hepatitis (AIH) is a chronic long-lasting hepatocellular inflammation associated with circulating auto antibodies. In addition to the genetic component, several cytokines have been implicated to be involved in AIH. This study was performed to investigate potential associations of AIH with IL4 gene variants.

METHOD

The studied alleles and genotypes included: IL4G/T allele polymorphisms at position -1098 and C/T allele polymorphisms at two positions (-33 and -590) on the IL4 gene, in addition to the A/G allele polymorphisms at position +1902 on the IL4RA gene.

RESULT

The IL4 C allele and CC genotype at position -590 and TT genotype at position -33 had a significantly higher frequency in AIH patients.

CONCLUSION

This study identified the IL4 C allele and CC genotype susceptibility gene in AIH, which will provide better insights into the mechanisms of AIH and potential therapeutic interventions.

Autoimmune Hepatitis in Brazilian Children: IgE and Genetic Polymorphisms in Associated Genes

Pediatric autoimmune hepatitis (AIH) patients present hypergammaglobulinemia, periportal CD8(+) cytotoxic T cell infiltration, and cirrhosis. Autoantibody profile defines AIH types 1 and 2 in addition to strong association with HLA-DRB1. We previously detected increased IgE serum levels and sought to compare clinical and histological features according to IgE levels in AIH (n = 74, ages 1-14 years) patients. Additionally, we typed 117 patients and 227 controls for functional polymorphisms of IL4, IL13, IL5, and IL4RA genes involved in IgE switching and eosinophil maturation that might contribute to overall genetic susceptibility to AIH. Serum IgE levels were high in 55% of AIH-1, but only in 12% of AIH-2 (P = 0.003) patients. Liver IgE was present in 91.3% of AIH-1 patients. The A alleles at both IL13 rs20541 and IL4RA rs1805011 were associated with AIH-1 (P = 0.024, OR = 1.55 and P < 0.0001, OR = 2.15, resp.). Furthermore, individuals presenting homozygosis for the A allele at IL4RA rs1805011 and HLA-DRB1(∗)03 and/or (∗)13 allele had sixfold greater risk to develop the disease (OR = 14.00, P < 0.001). The novel association suggests an additional role for IgE-linked immune response genes in the pathogenesis of AIH.

Immunity, tolerance and autoimmunity in the liver: A comprehensive review

The hepatic immune system is constantly exposed to a massive load of harmless dietary and commensal antigens, to which it must remain tolerant. Immune tolerance in the liver is mediated by a number of specialized antigen-presenting cells, including dendritic cells, Kupffer cells, liver sinusoidal endothelial cells and hepatic stellate cells. These cells are capable of presenting antigens to T cells leading to T cell apoptosis, anergy, or differentiation into regulatory T cells. However, the hepatic immune system must also be able to respond to pathogens and tumours and therefore must be equipped with mechanisms to override immune tolerance. The liver is a site of accumulation of a number of innate lymphocyte populations, including natural killer cells, CD56(+) T cells, natural killer T cells, γδ T cells, and mucosal-associated invariant T cells. Innate lymphocytes recognize conserved metabolites derived from microorganisms and host cells and respond by killing target cells or promoting the differentiation and/or activation of other cells of the immune system. Innate lymphocytes can promote the maturation of antigen-presenting cells from their precursors and thereby contribute to the generation of immunogenic T cell responses. These cells may be responsible for overriding hepatic immune tolerance to autoantigens, resulting in the induction and maintenance of autoreactive T cells that mediate liver injury causing autoimmune liver disease. Some innate lymphocyte populations can also directly mediate liver injury by killing hepatocytes or bile duct cells in murine models of hepatitis, whilst other populations may protect against liver disease. It is likely that innate lymphocyte populations can promote or protect against autoimmune liver disease in humans and that these cells can be targeted therapeutically. Here I review the cellular mechanisms by which hepatic antigen-presenting cells and innate lymphocytes control the balance between immunity, tolerance and autoimmunity in the liver.

Targeting the diverse immunological functions expressed by hepatic NKT cells

INTRODUCTION

NKT cells comprise approximately 30% of the hepatic lymphoid population in mice (∼ 50% in humans). Most mouse hepatic NKT cells [invariant (i)NKT cells] express T cell receptors, composed of invariant Vα14Jα18 chains. Unlike conventional T cells, iNKT cells recognize glycolipids presented in association with MHC class Ib (CD1d) molecules. Purportedly, iNKT cells serve key functions in several immunological events; the nature of these is often unclear. The consequences of hepatic iNKT cell activation can be beneficial or detrimental. α-Galactosylceramide stimulates the production of IFN-γ and IL-4. The reciprocal suppression exhibited by these cytokines limits the potential therapeutic value of α-galactosylceramide. Efforts are ongoing to develop α-galactosylceramide analogs that modulate iNKT cell activity and selectively promote IFN-γ or IL-4.

AREAS COVERED

An overview of hepatic iNKT cells and their purported role in liver disease. Efforts to develop therapeutic agents that promote their beneficial contributions.

EXPERT OPINION

While a growing body of literature documents the differential effects of α-GalCer analogs on IFN-γ and IL-4 production, the effects of these analogs on other iNKT cell activities remain to be determined. An exhaustive examination of the effects of these analogs on inflammation and liver injury in animal models remains prior to considering their utility in clinical trials.

Cytokine profiles affecting the pathogenesis of autoimmune hepatitis in Japanese patients

AIM

  Autoimmune hepatitis (AIH) is a chronic hepatitis of unknown etiology, although several cytokines have been implicated in its pathogenesis and severity. This study investigated the relationship between circulating cytokines in the pretreatment phase and remission following corticosteroid therapy phase in Japanese AIH patients.

METHODS

  A total of 28 cytokines were measured simultaneously by multiple bead array technology in the sera of 40 patients with AIH collected during pretreatment and remission phases.

RESULTS

  Interleukin (IL)-12p40, interferon-γ-inducible protein (IP-10), macrophage inflammatory protein (MIP)-1α, MIP-1β, IL-17F and IL-18 were significantly decreased during remission from pretreatment stage levels. The level of IP-10 in the pretreatment phase was correlated with serum levels of alanine aminotransferase.

CONCLUSION

  Our results suggest that a complex interplay of several cytokines, especially pro-inflammatory and T-helper 17 cytokines and regulatory T-cell suppression by IL-12p40 may play a pivotal role in the pathogenesis of AIH.

The most severe forms of type I autoimmune hepatitis are associated with genetically determined levels of TGF-beta1

We previously reported that paediatric (PAH) and adult (AAH) forms of type I autoimmune hepatitis (AH) have different HLA-associations and clinical outcome. In the present study we investigated the role of TGF-beta1 genetic polymorphisms in the different outcome of PAH and AAH. We found a significant increase of "high producer" 25GG genotype in PAH and 10CC in AAH. Low inflammation and low fibrosis in AAH was associated with the increase of codon 10CC (high producer) and codon 25CC (low producer) genotypes. The analysis in AAH of the two positions-haplotypes revealed that combined presence of 25GG and 10CC seems to neutralize the 10CC effect which remained in AAH having the 10CC(+)-25GG(-) haplotype. Altogether these results may explain, at least partially, the different clinical outcome of AAH and PAH.

Efficacy of ursodeoxycholic acid for Japanese patients with autoimmune hepatitis

PURPOSE

This study aimed to investigate the efficacy of ursodeoxycholic acid (UDCA) for Japanese patients with autoimmune hepatitis (AIH).

METHODS

One hundred forty-seven patients were investigated.

RESULTS

As initial treatment, 25 patients received UDCA (300-600 mg/day) monotherapy (UDCA group), 40 received a combination of prednisolone (PSL) (≥20 mg/day) and UDCA (combination group), 68 received PSL monotherapy (PSL group), and 14 received other treatments. During the follow-up, in the UDCA group, PSL was added to 8 of 12 patients failing to achieve the normalization of serum transaminase levels with UDCA monotherapy. Cumulative incidence of the normalization of serum transaminase levels was 64% in the UDCA group, 95% in the combination group, and 94% in the PSL group (log-rank test, P = 0.0001). UDCA group required longest periods until the normalization of serum transaminase levels. Eleven patients, who achieved persistent normalization of serum transaminase levels with UDCA monotherapy, did not reach liver failure or develop hepatocellular carcinoma for 49.7 (range = 13.4-137.3) months. Meanwhile, during the taper of PSL, doses of PSL at the initial relapse were lower in patients treated with PSL and UDCA than in those treated with PSL monotherapy, and initial relapse occurred earlier in patients treated with PSL monotherapy.

CONCLUSIONS

UDCA monotherapy is effective for some Japanese AIH patients; however, UDCA monotherapy for patients with either high-grade inflammatory activity or poor residual capacity of liver function is not recommended because they may reach liver failure before achievement of remission. Meanwhile, additional use of UDCA during the taper of corticosteroids may be effective for the prevention of early relapse.

mRNA expression of T-helper 1, T-helper 2 cytokines in autoimmune hepatitis in childhood

BACKGROUND

In the pathology of autoimmune hepatitis the immunity mechanism of T-helper 1 (Th1) and Th2 cells was recently evaluated. The purpose of the present study was to measure the mRNA levels in peripheral mononuclear cells and serum cytokines obtained from children with autoimmune hepatitis for a better understanding of the mechanism.

METHODS

Twenty-five patients with autoimmune hepatitis and seven controls were enrolled. mRNA levels in peripheral mononuclear cells and serum cytokines were measured using real-time polymerase chain reaction and immunoassay.

RESULTS

Serum interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) were rarely detected. In contrast the IFN-gamma/beta-actin mRNA levels were high.

CONCLUSION

Autoimmune hepatitis is a Th1-predominant state, therefore immune modulation therapies that target the control of Th1 cytokines should be used.

Hepatic NKT cells: friend or foe?

The innate immune system represents a critical first line of host response to infectious, injurious and inflammatory insults. NKT cells (natural killer T-cells) are an important, but relatively poorly understood, component of the innate immune response. Moreover, NKT cells are enriched within the liver, suggesting that within the hepatic compartment NKT cells probably fulfil important roles in the modulation of the immune response to infection or injury. NKT cells are characterized by their rapid activation and secretion of large amounts of numerous types of cytokines, including those within the Th1-type, Th2-type and Th17-type groups, which in turn can interact with a multitude of other cell types within the liver. In addition, NKT cells are capable of participating in a wide array of effector functions with regards to other cell types via NKT cell-surface-molecule expression [e.g. FASL (FAS ligand) and CD40L (CD40 ligand)] and the release of mediators (e.g. perforin and granzyme) contained in cellular granules, which in turn can activate or destroy other cells (i.e. immune or parenchymal cells) within the liver. Given the huge scope of potential actions that can be mediated by NKT cells, it has become increasingly apparent that NKT cells may fulfil both beneficial (e.g. clearance of virally infected cells) and harmful (e.g. induction of autoimmunity) roles in the setting of liver disease. This review will outline the possible roles which may be played by NKT cells in the setting of specific liver diseases or conditions, and will discuss the NKT cell in the context of its role as either a ‘friend’ or a ‘foe’ with respect to the outcome of these liver disorders.

Autoimmune hepatitis in Brazil: an overview

Autoimmune hepatitis is an immune cell-mediated chronic liver disease of unknown cause that leads, when untreated, to cirrhosis and liver failure. Importantly, this disease affects not only adults but children as well. Genetic susceptibility is clearly important and the major susceptibility factor identified up to now is the HLA-DRB1 locus, but other genes may play a role as well. HLA-DRB1 alleles present in South American patients differ from those found in patients in other parts of the world. In addition, we have recently identified two chromosomal regions where additional susceptibility factors may be found in Brazilian patients, namely, the class III MHC region and the 5q31 region where the IL-4 and IL-13 genes are located. This review discusses the current knowledge of the pathogenesis of this autoimmune disease occurring in the setting of an immune-privileged organ, the liver, and compares the data on gene polymorphisms studied in Brazil and in other parts of the world.

Association of the frequency of peripheral natural killer T cells with nonalcoholic fatty liver disease

AIM: To investigate whether changes in the frequency of peripheral natural killer T (NKT) cells were correlated with liver disease in patients who had metabolic predispositions to nonalcoholic fatty liver disease (NAFLD).

METHODS: Peripheral blood samples were obtained from 60 Chinese NAFLD patients and 60 age and gender matched healthy controls. The frequency of peripheral NKT cells was detected by flow cytometry. Clinical and laboratory data were collected for further analysis.

RESULTS: NAFLD patients had a lower frequency of peripheral NKT cells than healthy controls (1.21% ± 0.06% vs 1.62% ± 0.07%, P < 0.001). Further analysis revealed that the frequency of peripheral NKT cells was negatively correlated with body mass index, waist circumference and serum levels of alanine aminotransferase. Logistic regression analysis revealed that elevated body mass index [hazard ratio (HR): 2.991], aspartate aminotransferase levels (HR: 1.148) and fasting blood sugar (HR: 3.133) increased the risk of NAFLD, whereas an elevated frequency of peripheral NKT cells (HR: 0.107) decreased the risk.

CONCLUSION: Changes in the frequency of peripheral NKT cells were correlated with NAFLD and a decreased frequency of peripheral NKT cells was a risk factor for NAFLD.

Inhibition of p38 mitogen-activated protein kinase attenuates experimental autoimmune hepatitis: Involvement of nuclear factor kappa B

AIM: To investigate the role of p38 mitogen-activated protein kinase (p38MAPK) in murine experimental autoimmune hepatitis (EAH).

METHODS: To induce EAH, the syngeneic S-100 antigen emulsified in complete Freud's adjuvant was injected intraperitoneally into adult male C57Bl/6 mice. Liver injury was assessed by serum ALT and liver histology. The expression and activity of p38 MAPK were measured by Western blot and kinase activity assays. In addition, DNA binding activities of nuclear factor kappa B (NF-κB) were analyzed by electrophoretic mobility shift assay. The effects of SB203580, a specific p38 MAPK inhibitor, on liver injuries and expression of proinflammatory cytokines (interferon-γ, IL-12, IL-1β and TNF-α) were observed.

RESULTS: The activity of p38 MAPK and NF-κB was increased and reached its peak 14 or 21 d after the first syngeneic S-100 administration. Inhibition of p38 MAPK activation by SB203580 decreased the activation of NF-κB and the expression of proinflammatory cytokines. Moreover, hepatic injuries were improved significantly after SB203580 administration.

CONCLUSION: p38 MAPK and NF-κB play an important role in an animal model of autoimmune hepatitis (AIH) induced by autoantigens.

The Pro-Th1 Cytokine IL-12 Enhances IL-4 Production by Invariant NKT Cells: Relevance for T Cell-Mediated Hepatitis

IL-12 is essential for invariant NKT (iNKT) cells because it can maintain a functionally active population and promote a cytokine profile that is assumed to be mainly of the pro-Th1 type. We used the murine concanavalin A (Con A)-induced hepatitis model, in which iNKT cells, IL-12, IL-4, and IFN-gamma are equally requisite, to reevaluate this issue. We demonstrate that IL-12 interacts directly with iNKT cells, contributes to their recruitment to the liver, and enhances their IL-4 production, which is essential for disease onset. IL-12-deficient mice were less susceptible to experimental hepatitis and their iNKT cells produced less IL-4 than their wild-type counterpart. A normal response could be restored by IL-12 injection, revealing its importance as endogenous mediator. In accordance with this observation, we found that iNKT cells expressed the IL-12R constitutively, in contrast to conventional T cells. Furthermore, the physiological relevance of our data is supported by the lower susceptibility to disease induction of NOD mice, known for their inherent functional and numerical abnormalities of iNKT cells associated with decreased iNKT cell-derived IL-4 production and low IL-12 secretion. Taken together, our findings provide the first evidence that IL-12 can enhance the immune response through increased IL-4 production by iNKT cells, underscoring once more the functional plasticity of this subset.

Cytokines and chronic liver disease

From an immunological point of view, the healthy liver has been usually associated with the phenomenon of tolerance. A microenvironment of regulatory cytokines produced by liver Kuppfer cells and liver sinusoidal endothelial cells has contributed, together with resident dendritic cells, to generate a tolerogenic environment in this tissue. In this review we discussed the intrahepatic responses to different sorts of liver injury, such as hepatotrophic viruses, alcohol or putative self-antigens. In each case we analyzed the impact of different cytokines in the clinical outcome of the different pathological situations.

Expression of PD-1, PD-L1, and PD-L2 in the liver in autoimmune liver diseases

OBJECTIVES

PD-L1 (also B7-H1) and PD-L2 (also B7-DC) are ligands for programmed death-1 (PD-1), which is a member of the CD28/B7 superfamily of costimulatory molecules and plays an inhibitory role on the periphery. Impaired regulation of this system may cause disruption to self-tolerance leading to autoimmunity; however, the role of these molecules in the liver is unknown. Therefore, we examined the expression of PD-1, PD-L1, and PD-L2 in the liver in autoimmune liver diseases.

METHODS

We examined the liver expression of these molecules in autoimmune hepatitis (AIH) and primary biliary cirrhosis (PBC) with no previous medical treatment using immunohistochemical staining and real-time PCR, and compared with chronic hepatitis type C (CHC) as a control.

RESULTS

Although PD-1, PD-L1, and PD-L2 were expressed in the liver in AIH, PBC, as well as CHC, the expressions were relatively lower in PBC. In AIH, despite more severe inflammation than in CHC, the expression of these molecules was not greater than in CHC, and when compared with the relative expression of PD-L1, PD-L2 was lower in AIH. PD-L1 and PD-L2 expressions were well correlated with the level of IFN-gamma; however, relatively decreased induction for PD-L1 and PD-L2 by IFN-gamma was observed in AIH or PBC than in CHC.

CONCLUSION

Modulation of PD-1/PD-L1 and PD-L2 systems may play a role in the development of autoimmune liver diseases.

CCR5 in T Cell-Mediated Liver Diseases: What’s Going On?

The chemokine receptor CCR5 came into worldwide prominence a decade ago when it was identified as one of the major coreceptors for HIV infectivity. However, subsequent studies suggested an important modulatory role for CCR5 in the inflammatory response. Specifically, CCR5 has been reported to directly regulate T cell function in autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, and type 1 diabetes. Moreover, T cell-mediated immune responses are proposed to be critical in the pathogenesis of autoimmune and viral liver diseases, and recent clinical and experimental studies have also implicated CCR5 in the pathogenesis of autoimmune and viral liver diseases. Therefore, in this brief review, we highlight the evidence that supports an important role of CCR5 in the pathophysiology of T cell-mediated liver diseases with specific emphasis on autoimmune and viral liver diseases.

Liver infiltrating mononuclear cells in children with type 1 autoimmune hepatitis

OBJECTIVE

To investigate infiltrating cells in the liver of children with type 1 autoimmune hepatitis (AH-1).

METHODS

liver biopsies from 24 untreated AH-1 patients (14 children, 10 adults), five patients with hepatitis C virus related chronic hepatitis (HCV), and 10 control liver specimens (CL) were processed for immunohistochemical cell characterisation.

RESULTS

Two different cell distribution patterns were detected in the liver of patients with AH-1: (1) CD4(+) and CD20(+) cells were found in the central areas of the portal tracts (portal distribution); (2) CD8(+) cells were observed at the periphery of the portal space (periportal distribution). Some cell subsets, like CD56, CD57, Fas-L, and Bak, showed a non-defined distribution pattern. The presence of two well defined patterns of cell distribution was not observed in HCV and CL (CD4(+), CD20(+), and CD8(+) cells were uniformly distributed in the portal space). In AH-1 and CL, the NK markers CD56 and CD57 were found scattered throughout the liver parenchyma. However, in HCV biopsies, CD56(+) cells were also clearly increased in both the portal and the periportal areas. Biopsies of AH-1 and HCV patients showed a uniform distribution of Fas-L and Bak in the portal and periportal areas, with Bak staining also detected in the hepatic parenchyma.

CONCLUSIONS

Despite clinical and genetic differences, there was a similar distribution of liver infiltrating mononuclear cells in children and adults with AH-1. These results raise the possibility of reclassifying cryptogenic chronic hepatitis by immunohistochemical analysis of infiltrating liver cells.

Type 2 autoimmune hepatitis murine model: the influence of genetic background in disease development

Genetic predisposition is recognized as an important factor for the development of autoimmune hepatitis (AIH). To assess the potential contribution of MHC and non-MHC genes, type 2 AIH was reproduced in three mice strains, taking advantage of their different genetic makeup with regard to MHC and non-MHC genes. Mice (C57BL/6, 129/Sv and BALB/c) were DNA vaccinated with a pCMV-CTLA4-CYP2D6-FTCD plasmid coding for the extracellular region of CTLA-4 and for the antigenic region of the CYP2D6 and FTCD, and with pCMV-IL12. ALT and total IgG levels, liver histology, FACS analysis and liver T-cell cytotoxicity assays were monitored up to 8 months post-injection. C57BL/6 mice showed elevated serum ALT levels, autoantibodies, antigen-specific cytotoxic T-cells and lobular and periportal inflammatory infiltrate. The 129/Sv mice showed slightly elevated ALT levels, sparse liver lobular infiltrate and cytotoxic T-cells. The BALB/c mice showed no liver inflammation. All mice had elevated total serum IgG levels. This murine model of type 2 AIH shows that MHC and non-MHC genes contribute to the susceptibility to autoimmune hepatitis. The understanding of the genetic determinants implicated in AIH development will be a major advance in the study of its pathogenesis and could lead to a better diagnostic approach and preventive strategies.

The diverse functions of CD1d-restricted NKT cells and their potential for immunotherapy

CD1d-restricted NKT cells have been identified as an important component of the immune system that have the capacity both to augment beneficial host immunity and to prevent harmful autoimmunity. These cells have the ability to produce a wide variety of cytokines, including both proinflammatory and antiinflammatory cytokines that can have multiple different effects on the outcome of immune reactions. The discovery that these T cells are activated by specific recognition of glycolipids in the glycosylceramide family has led to new approaches to manipulate the pleiotropic functions of these cells. Here, we review the multiple activities that have been attributed to NKT cells in a variety of different disease models, and the current state of our understanding of the mechanisms that control the functional outcome of NKT cell activation.