Cytochrome P4502D6(193-212): a new immunodominant epitope and target of virus/self cross-reactivity in liver kidney microsomal autoantibody type 1-positive liver disease

Detection of polyreactive immunoglobulin G facilitates diagnosis in children with autoimmune hepatitis

OBJECTIVE

The detection of autoantibodies is essential to diagnose autoimmune hepatitis (AIH). Particularly in children, specificity of autoantibodies decreases due to lower titers being diagnostic and being present not only in AIH but also in other liver diseases. Recently, quantification of polyreactive IgG (pIgG) for detection of adult AIH showed the highest overall accuracy compared to antinuclear antibodies (ANA), anti-smooth muscle antibodies (anti-SMA), anti-liver kidney microsomal antibodies (anti-LKM) and anti-soluble liver antigen/liver pancreas antibodies (anti-SLA/LP). We aimed to evaluate the diagnostic value of pIgG for pediatric AIH.

DESIGN

pIgG, quantified using HIP1R/BSA coated ELISA, and immunofluorescence on rodent tissue sections were performed centrally. The diagnostic fidelity to diagnose AIH was compared to conventional autoantibodies of AIH in training and validation cohorts from a retrospective, European multi-center cohort from nine centers from eight European countries composed of existing biorepositories from expert centers (n = 285).

RESULTS

IgG from pediatric AIH patients exhibited increased polyreactivity to multiple protein and non-protein substrates compared to non-AIH liver diseases and healthy children. pIgG had an AUC of 0.900 to distinguish AIH from non-AIH liver diseases. pIgG had a 31-73% higher specificity than ANA and anti-SMA and comparable sensitivity that was 6-20 times higher than of anti-SLA/LP, anti-LC1 and anti-LKM. pIgG had a 21-34% higher accuracy than conventional autoantibodies, was positive in 43-75% of children with AIH and normal IgG and independent from treatment response.

CONCLUSION

Detecting pIgG improves the diagnostic evaluation of pediatric AIH compared to conventional autoantibodies, primarily owing to higher accuracy and specificity.

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.

Molecular mimicry and autoimmunity in the time of COVID-19

Infectious diseases are commonly implicated as potential initiators of autoimmune diseases (ADs) and represent the most commonly known factor in the development of autoimmunity in susceptible individuals. Epidemiological data and animal studies on multiple ADs suggest that molecular mimicry is one of the likely mechanisms for the loss of peripheral tolerance and the development of clinical disease. Besides molecular mimicry, other mechanisms such as defects in central tolerance, nonspecific bystander activation, epitope-determinant spreading, and/or constant antigenic stimuli, may also contribute for breach of tolerance and to the development of ADs. Linear peptide homology is not the only mechanism by which molecular mimicry is established. Peptide modeling (i.e., 3D structure), molecular docking analyses, and affinity estimation for HLAs are emerging as critical strategies when studying the links of molecular mimicry in the development of autoimmunity. In the current pandemic, several reports have confirmed an influence of SARS-CoV-2 on subsequent autoimmunity. Bioinformatic and experimental evidence support the potential role of molecular mimicry. Peptide dimensional analysis requires more research and will be increasingly important for designing and distributing vaccines and better understanding the role of environmental factors related to autoimmunity.

Incorporating the Molecular Mimicry of Environmental Antigens into the Causality of Autoimmune Hepatitis

Molecular mimicry between foreign and self-antigens has been implicated as a cause of autoimmune hepatitis in experimental models and cross-reacting antibodies in patients. This review describes the experimental and clinical evidence for molecular mimicry as a cause of autoimmune hepatitis, indicates the limitations and uncertainties of this premise, and encourages investigations that assess diverse environmental antigens as sources of disease-relevant molecular mimics. Pertinent articles were identified in PubMed using multiple search phrases. Several pathogens have linear or conformational epitopes that mimic the self-antigens of autoimmune hepatitis. The occurrence of an acute immune-mediated hepatitis after vaccination for severe acute respiratory syndrome (SARS)-associated coronavirus 2 (SARS-CoV-2) has suggested that vaccine-induced peptides may mimic disease-relevant tissue antigens. The intestinal microbiome is an under-evaluated source of gut-derived antigens that could also engage in molecular mimicry. Chaperone molecules may enhance the pathogenicity of molecular mimics, and they warrant investigation. Molecular mimics of immune dominant epitopes within cytochrome P450 IID6, the autoantigen most closely associated with autoimmune hepatitis, should be sought in diverse environmental antigens and assessed for pathogenicity. Avoidance strategies, dietary adjustments, vaccine improvement, and targeted manipulation of the intestinal microbiota may emerge as therapeutic possibilities. In conclusion, molecular mimicry may be a missing causality of autoimmune hepatitis. Molecular mimics of key immune dominant epitopes of disease-specific antigens must be sought in diverse environmental antigens. The ubiquity of molecular mimicry compels rigorous assessments of peptide mimics for immunogenicity and pathogenicity in experimental models. Molecular mimicry may complement epigenetic modifications as causative mechanisms of autoimmune hepatitis.

Liver kidney microsome antibodies. Analysis of a laboratory series

Objectives

The objectives were to characterize the liver kidney microsome (LKM) antibody profile of a 14-month-old girl with autoimmune hepatitis and analyze the laboratory prevalence of LKM positivity.

Design and methods

This is retrospective analysis of the LKM antibody immunofluorescence tests performed by the Immunology Laboratory of Johns Hopkins Hospital from September 8, 2020 to July 31, 2022. LKM positive sera were also tested by an ELISA for LKM1 antibodies, which recognize the cytochrome P450 2D6 antigen. In silico analysis of 2D6 mRNA expression across anatomical sites was performed using Bgee and GTEx Portal databases.

Results

Of the total of 1598 patients (893 F, 705 M, ages 0.8-94 years) tested for LKM antibodies, 3 were positive, yielding a 0.2% period prevalence. The clinical diagnosis was autoimmune hepatitis in the index case, acute viral hepatitis in a 3-yo male, and hepatocellular carcinoma in a 54-yo male. LKM antibodies yielded the classical homogenous staining pattern in the liver cytosol and proximal kidney tubular cells. The first two patients were also positive for LKM1 antibodies, whereas the third was negative. 2D6 mRNA was expressed highly in the liver, moderately in the duodenum, and minimally in other tissues.

Conclusions

Overall, LKM antibodies are rare. They contribute to establish a diagnosis of autoimmune hepatitis, although they are also found in other liver diseases. The cytochrome P450 2D6 is one of the antigens recognized by LKM antibodies, but other antigens are likely targeted considering that 2D6 is minimally expressed in the kidney and yet LKM antibodies bind to kidney tubuli.

Impact of Antigen Presentation Mechanisms on Immune Response in Autoimmune Hepatitis

The liver is a very tolerogenic organ. It is continually exposed to a multitude of antigens and is able to promote an effective immune response against pathogens and simultaneously immune tolerance against self-antigens. In spite of strong peripheral and central tolerogenic mechanisms, loss of tolerance can occur in autoimmune liver diseases, such as autoimmune hepatitis (AIH) through a combination of genetic predisposition, environmental factors, and an imbalance in immunological regulatory mechanisms. The liver hosts several types of conventional resident antigen presenting cells (APCs) such as dendritic cells, B cells and macrophages (Kupffer cells), and unconventional APCs including liver sinusoidal endothelial cells, hepatic stellate cells and hepatocytes. By standard (direct presentation and cross-presentation) and alternative mechanisms (cross-dressing and MHC class II-dressing), liver APCs presents self-antigen to naive T cells in the presence of costimulation leading to an altered immune response that results in liver injury and inflammation. Additionally, the transport of antigens and antigen:MHC complexes by trogocytosis and extracellular vesicles between different cells in the liver contributes to enhance antigen presentation and amplify autoimmune response. Here, we focus on the impact of antigen presentation on the immune response in the liver and on the functional role of the immune cells in the induction of liver inflammation. A better understanding of these key pathogenic aspects could facilitate the establishment of novel therapeutic strategies in AIH.

Autoimmune Hepatitis: Serum Autoantibodies in Clinical Practice

Circulating autoantibodies are a key diagnostic tool in autoimmune hepatitis (AIH), being positive in 95% of the cases if tested according to dedicated guidelines issued by the International Autoimmune Hepatitis Group. They also allow the distinction between type 1 AIH, characterized by positive anti-nuclear and/or anti-smooth muscle antibody, and type 2 AIH, characterized by positive anti-liver kidney microsomal type 1 and/or anti-liver cytosol type 1 antibody. Anti-soluble liver antigen is the only AIH-specific autoantibody, and is found in 20-30% of both type 1 and type 2 AIH. Anti-neutrophil cytoplasmic antibody is frequently positive in type 1 AIH, being associated also with inflammatory bowel disease and with primary/autoimmune sclerosing cholangitis. The reference method for autoantibody testing remains indirect immunofluorescence on triple tissue (rodent liver, kidney and stomach), allowing both the detection of the majority of liver-relevant reactivities, including those autoantibodies whose molecular target antigens are unknown. Of note, the current knowledge of the clinical significance of autoantibodies relies on studies based on this technique. However, immunofluorescence requires trained laboratory personnel, is observer-dependent, and lacks standardization, leading to ongoing attempts at replacing this method with automated assays, the sensitivity, and specificity of which, however, require further studies before they can be used as a reliable alternative to immunofluorescence; currently, they may be used as complementary to immunofluorescence.

Impact of genetic and environmental factors on autoimmune hepatitis

Autoimmune hepatitis (AIH) is a chronic non-resolving liver disease characterized by diffuse hypergammaglobulinemia, the presence of autoantibodies and characteristic histological findings. The disease can have catastrophic outcome with the development of end-stage liver disease if misdiagnosed/undiagnosed and left untreated. AIH pathogenesis remains obscure and the main hypothesis supports its development in genetically predisposed individuals after being exposed to certain environmental triggers. Genetic predisposition is linked to the presence of certain HLA alleles, mainly HLA-DR3 and HLA-DR4. However, a wide number of non-HLA epitopes have also been associated with the disease although data vary significantly among different ethnic groups. Therefore, it is likely that epigenetic alterations may also play a crucial role in disease's pathogenesis, although not yet extensively studied. The aim of this review was to summarize the genetic and environmental factors that have been associated with AIH, but also to open new insights towards the role of epigenetic modifications in the etiology of the disease.

Etiopathogenesis and Diagnostic Strategies in Autoimmune Hepatitis

Autoimmune hepatitis (AIH) is a chronic liver disease with the incidence of 10 to 17 per 100,000 people in Europe. It affects people of any age, but most often occurs in the 40-60 age group. The clinical picture is varied, from asymptomatic to severe acute hepatitis or liver failure. The disease onset is probably associated with the impaired function of T lymphocytes, the development of molecular mimicry, intestinal dysbiosis, or infiltration with low density neutrophils, which, alongside autoantibodies (i.e., ANA, ASMA), implicate the formation of neutrophil extracellular traps (NETs), as a component of the disease process, and mediate the inappropriate immune response. AIH is characterized with an increased activity of aminotransferases, elevated concentration of serum immunoglobulin G, the presence of circulating autoantibodies and liver inflammation. The result of the histological examination of the liver and the presence of autoantibodies, although not pathognomonic, still remain a distinguishing feature. The diagnosis of AIH determines lifelong treatment in most patients. The treatment is implemented to prevent the development of cirrhosis and end-stage liver failure. This work focuses mainly on the etiopathogenesis and diagnosis of AIH.

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.

Antigen-Specific Immunotherapy for Treatment of Autoimmune Liver Diseases

The liver is a critical organ in controlling immune tolerance. In particular, it is now clear that targeting antigens for presentation by antigen presenting cells in the liver can induce immune tolerance to either autoantigens from the liver itself or tissues outside of the liver. Here we review immune mechanisms active within the liver that contribute both to the control of infectious diseases and tolerance to self-antigens. Despite its extraordinary capacity for tolerance induction, the liver remains a target organ for autoimmune diseases. In this review, we compare and contrast known autoimmune diseases of the liver. Currently patients tend to receive strong immunosuppressive treatments and, in many cases, these treatments are associated with deleterious side effects, including a significantly higher risk of infection and associated health complications. We propose that, in future, antigen-specific immunotherapies are adopted for treatment of liver autoimmune diseases in order to avoid such adverse effects. We describe various therapeutic approaches that either are in or close to the clinic, highlight their mechanism of action and assess their suitability for treatment of autoimmune liver diseases.

Gut Microbiota and Liver Injury (II): Chronic Liver Injury

Chronic liver injury mainly comprises viral hepatitis, fatty liver disease, autoimmune hepatitis, cirrhosis and liver cancer. It is well established that gut microbiota serves as the key upstream modulator for chronic liver injury progression. Indeed, the term "gut-liver axis" was mostly applied for chronic liver injury. In the current chapter, we will summarize the relationship between gut microbiota and chronic liver injury, including the interaction between them based on latest clinic and basic research.

Examining pathogenic concepts of autoimmune hepatitis for cues to future investigations and interventions

BACKGROUND

Multiple pathogenic mechanisms have been implicated in autoimmune hepatitis, but they have not fully explained susceptibility, triggering events, and maintenance or escalation of the disease. Furthermore, they have not identified a critical defect that can be targeted. The goals of this review are to examine the diverse pathogenic mechanisms that have been considered in autoimmune hepatitis, indicate investigational opportunities to validate their contribution, and suggest interventions that might evolve to modify their impact. English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed. Genetic and epigenetic factors can affect susceptibility by influencing the expression of immune regulatory genes. Thymic dysfunction, possibly related to deficient production of programmed cell death protein-1, can allow autoreactive T cells to escape deletion, and alterations in the intestinal microbiome may help overcome immune tolerance and affect gender bias. Environmental factors may trigger the disease or induce epigenetic changes in gene function. Molecular mimicry, epitope spread, bystander activation, neo-antigen production, lymphocytic polyspecificity, and disturbances in immune inhibitory mechanisms may maintain or escalate the disease. Interventions that modify epigenetic effects on gene expression, alter intestinal dysbiosis, eliminate deleterious environmental factors, and target critical pathogenic mechanisms are therapeutic possibilities that might reduce risk, individualize management, and improve outcome. In conclusion, diverse pathogenic mechanisms have been implicated in autoimmune hepatitis, and they may identify a critical factor or sequence that can be validated and used to direct future management and preventive strategies.

Autoimmune Hepatitis, Sclerosing Cholangitis, and Autoimmune Sclerosing Cholangitis or Overlap Syndrome

Autoimmune hepatitis (AIH) is characterized by elevated serum aminotransferases, immunoglobulin G, autoantibodies, and interface hepatitis, in the absence of a known diagnosis. Presentation is varied. Therapy is with immunosuppression. There is inflammation of the intrahepatic and/or extrahepatic bile ducts in Sclerosing cholangitis (SC) and when associated with inflammatory bowel disease, it is known as primary SC, with Ursodeoxycholic acid used for therapy. The overlap of clinical, biochemical and histological features of AIH and PSC is known as autoimmune sclerosing cholangitis (ASC) or overlap syndrome. Liver transplantation is performed when medical treatment fails and both AIH and PSC may recur post-transplantation.

Pathogens and autoimmune hepatitis

Autoimmune hepatitis (AIH) is a severe form of hepatitis resulting in the autoimmune-mediated destruction of the liver parenchyma. Whereas many of the immunopathogenic events have been elucidated and some of the drivers of the disease have been identified, little is known about the aetiology of the disease. There are certain risk factors, such as particular human leucocyte antigen (HLA) haplotypes, that enhance the susceptibility for AIH or influence the severity of the disease. However, as for many other autoimmune diseases, the mere presence of such risk factors does not warrant the occurrence of the disease. Not all individuals carrying risk factors develop AIH, and not all patients with AIH are carriers of high-risk alleles. Thus, additional environmental factors need to be considered as triggers for AIH. Environmental factors include diet, sunlight exposure, stress, medication and hygiene, as well as pathogen infections and vaccinations. This review discusses if pathogens should be considered as triggers for the initiation and/or propagation of AIH.

Animal models of autoimmune hepatitis

Many animal models for autoimmune hepatitis (AIH) have been described in the past. Most models had to deal with the relative immunosuppressive environment of the liver. Therefore, some models used a combination of several triggering factors often on a susceptible background to generate an aggressive immune response that targets the liver. In addition, in order to be able to track the immune response the models used specific model autoantigens as targets that are either not present or have not been identified as a natural autoantigen in AIH patients. Thereby the feasibility of such models is somewhat questionable. Although many historic approaches included challenges of experimental animals with liver homogenates it was only in the last decade that natural occurring liver autoantigens have been used in animal models. This article reflects on the requirements for breaking liver tolerance and on how an ideal experimental model for AIH would look like. In addition, it discusses historic as well as recent animal models in the context of feasibility of induction, similarity of the clinical outcome to human AIH, and gain of knowledge for possible future therapies.

Autoantibodies in Autoimmune Hepatitis: Can Epitopes Tell Us about the Etiology of the Disease?

Autoimmune hepatitis (AIH), primary biliary cholangitis (PBC), and primary sclerosing cholangitis (PSC) are serious autoimmune liver diseases that are characterized by a progressive destruction of the liver parenchyma and/or the hepatic bile ducts and the development of chronic fibrosis. Left untreated autoimmune liver diseases are often life-threatening, and patients require a liver transplantation to survive. Thus, an early and reliable diagnosis is paramount for the initiation of a proper therapy with immunosuppressive and/or anticholelithic drugs. Besides the analysis of liver biopsies and serum markers indicating liver damage, the screening for specific autoantibodies is an indispensable tool for the diagnosis of autoimmune liver diseases. Such liver autoantigen-specific antibodies might be involved in the disease pathogenesis, and their epitope specificity may give some insight into the etiology of the disease. Here, we will mainly focus on the generation and specificity of autoantibodies in AIH patients. In addition, we will review data from animal models that aim toward a better understanding of the origins and pathogenicity of such autoantibodies.

Intestinal microbiome and permeability in patients with autoimmune hepatitis

Autoimmune hepatitis (AIH) is a severe inflammatory liver disease. The underlying mechanisms remain unclear, but recent studies provided new perspectives on altered intestinal microbiome and permeability in AIH animal models and patients, highlighting gut-liver crosstalk in the pathogenesis of AIH. Transgenic AIH mice carrying HLA-DR3 showed reduced diversity and total load of gut microbiota. Germ-free mice are resistant to concanavalin A-induced liver injury, whereas enterogenouss antigens induce the activation of natural killer T cells participating in concanavalin A-induced liver injury, supporting the close relationship between microbiota and AIH. Moreover, 'molecular mimicry' provides a plausible interpretation of the immune reactions between microorganic antigens and liver autoantigens, for instance, cytochrome P4502D6, the target of cross-reactivity between virus and self. Nevertheless, direct evidence for the intestinal microbiome and permeability in AIH is still limited. The relationship between AIH susceptibilities and an intestinal microbiome shaped by drugs, diets or genes needs further study.

"Autoimmune(-Like)" Drug and Herb Induced Liver Injury: New Insights into Molecular Pathogenesis

Idiosyncratic drug-induced liver injury (DILI) and hepatic injury due to herbal and dietary supplements (HDS) can adapt clinical characteristics of autoimmune hepatitis (AIH), such as the appearance of autoantibodies and infiltration of the liver by immune competent cells. To describe these cases of DILI/HDS, the poorly-defined term "autoimmune(-like)" DILI/HDS came up. It is uncertain if these cases represent a subgroup of DILI/HDS with distinct pathomechanistic and prognostic features different from "classical" DILI/HDS. Besides, due to the overlap of clinical characteristics of "immune-mediated" DILI/HDS and AIH, both entities are not easy to differentiate. However, the demarcation is important, especially with regard to treatment: AIH requires long-term, mostly lifelong immunosuppression, whereas DILI/HDS does not. Only through exact diagnostic evaluation, exclusion of differential diagnoses and prolonged follow-up can the correct diagnosis reliably be made. Molecular mechanisms have not been analysed for the subgroup of "autoimmune(-like)" DILI/HDS yet. However, several pathogenetic checkpoints of DILI/HDS in general and AIH are shared. An analysis of these shared mechanisms might hint at relevant molecular processes of "autoimmune(-like)" DILI/HDS.

Clinical usefulness of serum antibodies as biomarkers of gastrointestinal and liver diseases

The progressively growing knowledge of the pathophysiology of a number of immune-mediated gastrointestinal and liver disorders, including autoimmune atrophic gastritis, coeliac disease, autoimmune enteropathy, inflammatory bowel disease, autoimmune hepatitis, primary sclerosing cholangitis, primary biliary cholangitis and autoimmune pancreatitis, together with the improvement of their detection methods have increased the diagnostic power of serum antibodies. In some cases - coeliac disease and autoimmune atrophic gastritis - they have radically changed gastroenterologists' diagnostic ability, while in others - autoimmune hepatitis, inflammatory bowel disease and autoimmune pancreatitis - their diagnostic performance is still inadequate. Of note, serum antibody misuse in clinical practice has raised a number of controversies, which may generate confusion in the diagnostic management of the aforementioned disorders. In this review, we critically re-evaluate the usefulness of serum antibodies as biomarkers of immune-mediated gastrointestinal and liver disorders, and discuss their pitfalls and merits.

Global Disparities and Their Implications in the Occurrence and Outcome of Autoimmune Hepatitis

Autoimmune hepatitis has a variable occurrence, clinical phenotype, and outcome, and the factors contributing to this variability are uncertain. The goals of this review are to examine the global disparities in the occurrence and outcome of autoimmune hepatitis, suggest bases for these disparities, and encourage investigations that extend beyond single-center experiences. Disparities in the incidence and prevalence of autoimmune hepatitis in different age groups, genders, ethnicities, and geographical regions suggest that factors other than genetic predisposition are involved. Age- and gender-related antigen exposures from the external (infections, toxins, and medications) and internal (intestinal microbiome) environment may affect the incidence of the disease, and the timeliness and nature of treatment may influence its prevalence. The increasing incidence of autoimmune hepatitis in Spain, Denmark, and the Netherlands suggests that a new etiological trigger has been introduced or that the susceptible population has changed. Variations in mortality between Western and Asian-Pacific countries may result from differences in disease detection or management, and variations in gender predilection, peak age of onset, frequency of concurrent immune diseases, and serological profile may reflect gender-biased and age-related antigen exposures and genetic predispositions. Global collaborations, population-based epidemiological studies that identify case clustering, and controlled interview-based surveys are mechanisms by which to understand these disparities and improve management. In conclusion, autoimmune hepatitis has a rising incidence in some countries and variable occurrence, phenotype, and outcome between countries and subgroups within countries. These disparities suggest that unrecognized population-based environmental, infectious, or socioeconomic factors are affecting its character.

Diagnostic approach to autoimmune hepatitis

INTRODUCTION

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease which, if left without treatment, can evolve into cirrhosis and possibly liver failure. The diagnosis of AIH is hampered by the lack of specific and reliable markers of the disease and a number of clinical, biochemical, immunological, histological and genetic factors should be considered to reach a confident diagnosis Areas covered: Clinical expression of AIH, histological features, serological and genetic profiles, differential diagnosis, overlap with other autoimmune liver diseases, assessed on the basis of personal experience and review of published literature in the last 10 years through a systematic Medline search (keywords: autoimmune hepatitis, diagnosis) Expert commentary: Notwithstanding numerous efforts to identify simple and reliable markers of the disease, the diagnosis of AIH is still based on the combination of histological, immunological and biochemical features and often can represent a real challenge for the hepatologist.

Liver immunology: How to reconcile tolerance with autoimmunity

There are several examples of liver tolerance: the relative ease by which liver allografts are accepted and the exploitation of the hepatic microenvironment by the malarial parasite and hepatotrophic viruses are notable examples. The vasculature of the liver supports a unique population of antigen presenting cells specialised to maintain immunological tolerance despite continuous exposure to gut-derived antigens. Liver sinusoidal endothelial cells and Kupffer cells appear to be key to the maintenance of immune tolerance, by promoting T cell anergy or deletion and the generation of regulatory cell subsets. Despite this, there are three liver diseases with likely autoimmune involvement: primary biliary cirrhosis, primary sclerosing cholangitis and autoimmune hepatitis. How can we reconcile this with the inherent tolerogenicity of the liver? Genetic studies have uncovered several associations with genes involved in the activation of the innate and adaptive immune systems. There is also evidence pointing to pathogenic and xenobiotic triggers of autoimmune liver disease. Coupled to this, impaired immunoregulatory mechanisms potentially play a permissive role, allowing the autoimmune response to proceed.

De novo autoimmune hepatitis after liver transplantation: A focus on glutathione S-transferase theta 1

De novo autoimmune hepatitis (DAIH) is a rare clinical condition with features that resemble those of autoimmune hepatitis (AIH) in patients undergoing liver transplantation (LT) for nonautoimmune liver disease. The diagnosis of this entity has been based on the presence of biochemical and histological patterns similar to those observed in the primary AIH, although several considerations must be taken into account. The impact of DAIH on graft survival is relevant, and early diagnosis and treatment is associated with a good longterm outcome. Although glutathione S-transferase theta 1 (GSTT1) alloimmune recognition has been shown to be involved in the pathogenesis of DAIH, further studies are necessary to fully determine its pathogenic mechanisms and risk factors. We review the pathophysiology, the most common histological patterns, the treatment strategies, and the longterm outcomes of DAIH after LT with a special focus on GSTT1. Liver Transplantation 23:75-85 2017 AASLD.

Immunopathogenic Mechanisms of Autoimmune Hepatitis: How Much Do We Know from Animal Models?

Autoimmune hepatitis (AIH) is characterized by a progressive destruction of the liver parenchyma and a chronic fibrosis. The current treatment of autoimmune hepatitis is still largely dependent on the administration of corticosteroids and cytostatic drugs. For a long time the development of novel therapeutic strategies has been hampered by a lack of understanding the basic immunopathogenic mechanisms of AIH and the absence of valid animal models. However, in the past decade, knowledge from clinical observations in AIH patients and the development of innovative animal models have led to a situation where critical factors driving the disease have been identified and alternative treatments are being evaluated. Here we will review the insight on the immunopathogenesis of AIH as gained from clinical observation and from animal models.

Factoring the intestinal microbiome into the pathogenesis of autoimmune hepatitis

The intestinal microbiome is a reservoir of microbial antigens and activated immune cells. The aims of this review were to describe the role of the intestinal microbiome in generating innate and adaptive immune responses, indicate how these responses contribute to the development of systemic immune-mediated diseases, and encourage investigations that improve the understanding and management of autoimmune hepatitis. Alterations in the composition of the intestinal microflora (dysbiosis) can disrupt intestinal and systemic immune tolerances for commensal bacteria. Toll-like receptors within the intestine can recognize microbe-associated molecular patterns and shape subsets of T helper lymphocytes that may cross-react with host antigens (molecular mimicry). Activated gut-derived lymphocytes can migrate to lymph nodes, and gut-derived microbial antigens can translocate to extra-intestinal sites. Inflammasomes can form within hepatocytes and hepatic stellate cells, and they can drive the pro-inflammatory, immune-mediated, and fibrotic responses. Diet, designer probiotics, vitamin supplements, re-colonization methods, antibiotics, drugs that decrease intestinal permeability, and molecular interventions that block signaling pathways may emerge as adjunctive regimens that complement conventional immunosuppressive management. In conclusion, investigations of the intestinal microbiome are warranted in autoimmune hepatitis and promise to clarify pathogenic mechanisms and suggest alternative management strategies.

Cirrhosis and autoimmune liver disease: Current understanding

Primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH) constitute the classic autoimmune liver diseases (AILDs). While AIH target the hepatocytes, in PBC and PSC the targets of the autoimmune attack are the biliary epithelial cells. Persistent liver injury, associated with chronic AILD, leads to un-resolving inflammation, cell proliferation and the deposition of extracellular matrix proteins by hepatic stellate cells and portal myofibroblasts. Liver cirrhosis, and the resultant loss of normal liver function, inevitably ensues. Patients with cirrhosis have higher risks or morbidity and mortality, and that in the decompensated phase, complications of portal hypertension and/or liver dysfunction lead to rapid deterioration. Accurate diagnosis and monitoring of cirrhosis is, therefore of upmost importance. Liver biopsy is currently the gold standard technique, but highly promising non-invasive methodology is under development. Liver transplantation (LT) is an effective therapeutic option for the management of end-stage liver disease secondary to AIH, PBC and PSC. LT is indicated for AILD patients who have progressed to end-stage chronic liver disease or developed intractable symptoms or hepatic malignancy; in addition, LT may also be indicated for patients presenting with acute liver disease due to AIH who do not respond to steroids.

Contemporary issues and future directions in autoimmune hepatitis

Autoimmune hepatitis (AIH) is a severe life-threatening hepatopathy of unknown etiology, affecting both pediatric and adult populations, and characterised by inflammatory liver histology, circulating non-organ-specific autoantibodies, and hypergammaglobulinaemia. AIH is a very heterogeneous disease with a variety of clinical presentations, ranging from asymptomatic liver test abnormalities to acute severe hepatitis or even acute liver failure. It responds very well to immunosuppressive treatment with prednisolone with or without azathioprine. Patients who are intolerant or fail to respond to standard therapy are candidates for alternative immunosuppressive regimens, the combination of steroids with mycophenolate mofetil or calcineurin inhibitors being the most frequently reported. The pathogenesis of AIH remains not completely understood, although there is evidence that genetic predisposition, molecular mimicry and defective immunoregulatory mechanisms contribute to the autoimmune liver damage. Areas covered: A literature search was conducted using the key-words 'autoimmune hepatitis', 'immunogenetics', 'regulatory T-cells' and 'immunosuppression'. The aim of this review is to discuss recent breakthroughs in the understanding AIH pathogenesis, diagnosis and treatment. Expert commentary: Progress in the understanding of AIH pathogenesis is likely to contribute to the development of novel therapeutic strategies, such as the adoptive transfer of autologous expanded antigen-specific regulatory T-cells.

Cutting edge issues in autoimmune hepatitis

Autoimmune hepatitis (AIH) is a severe liver disease affecting all age groups worldwide. Novel basic and clinical aspects of AIH, addressed at a Monothematic Conference in London in September 2015, are highlighted in this review. The diagnosis of AIH relies upon detection of characteristic autoantibodies, hypergammaglobulinemia, and interface hepatitis on liver histology. The International Autoimmune Hepatitis Group (IAIHG) has devised diagnostic scoring systems to help in comparative studies and clinical practice. AIH arises in a genetically predisposed host, when yet unknown triggers - such an encounter with a pathogen - lead to a T cell-mediated immune response targeting liver autoantigens. This immune response is inadequately controlled because regulatory mechanisms are impaired. The mainstay of treatment for AIH is immunosuppression, which should be instituted as soon as the diagnosis is made. Standard treatment regimens include relatively high doses of predniso(lo)ne, which are tapered gradually as azathioprine is introduced. Recent guidelines have described newer treatment regimens and have tightened the goal of therapy to complete normalization of biochemical, serological and histological parameters. Mycophenolate mofetil, calcineurin inhibitors, mTOR inhibitors and biological agents are potential salvage therapies, but should be reserved for selected non-responsive patients and administered only in experienced centers. Liver transplantation is a life-saving option for those patients who progress to end-stage liver disease. Further dissection of cellular and molecular pathways involved in AIH pathogenesis is likely to lead to the discovery of novel, tailored and better tolerated therapies.

Autoimmune hepatitis: From mechanisms to therapy

Autoimmune hepatitis (AIH) is a progressive inflammatory hepatopathy and an important cause of end-stage liver disease. Its aetiology remains unknown, though both genetic and environmental factors are involved in its development. The major mechanism of autoimmune liver damage involves immune reactions against host liver antigens. Numerical and functional defects of regulatory T-cells play a permissive role enabling autoimmune liver injury to occur and persist. The most typical features of AIH are female preponderance, hypergammaglobulinaemia, seropositivity for circulating autoantibodies and a picture of interface hepatitis on histology. Two types of AIH are distinguished according to serological profile: AIH type 1 patients are positive for anti-nuclear and/or anti-smooth muscle antibodies, whereas AIH type 2 patients are defined by the positivity for anti-liver kidney microsomal type 1 antibody and/or for anti-liver cytosol type 1 antibody. Clinical manifestations are variable, and AIH onset is often ill-defined, frequently mimicking acute hepatitis; its course may be fluctuating. AIH responds to immunosuppressive treatment in the majority of cases. Steroids with or without azathioprine should be instituted promptly upon diagnosis. Remission is achieved in some 80% of patients. For the remaining 20% of patients, alternative immunosuppressive agents such as mycophenolate mofetil and calcineurin inhibitors are an option. Liver transplantation should be considered for those patients who progress to cirrhosis and develop complications of end-stage liver disease, as well as for those presenting with acute liver failure; outcomes are excellent, although the disease may recur in the allograft.

Impact of physiological, pathological and environmental factors on the expression and activity of human cytochrome P450 2D6 and implications in precision medicine

With only 1.3-4.3% in total hepatic CYP content, human CYP2D6 can metabolize more than 160 drugs. It is a highly polymorphic enzyme and subject to marked inhibition by a number of drugs, causing a large interindividual variability in drug clearance and drug response and drug-drug interactions. The expression and activity of CYP2D6 are regulated by a number of physiological, pathological and environmental factors at transcriptional, post-transcriptional, translational and epigenetic levels. DNA hypermethylation and histone modifications can repress the expression of CYP2D6. Hepatocyte nuclear factor-4α binds to a directly repeated element in the promoter of CYP2D6 and thus regulates the expression of CYP2D6. Small heterodimer partner represses hepatocyte nuclear factor-4α-mediated transactivation of CYP2D6. GW4064, a farnesoid X receptor agonist, decreases hepatic CYP2D6 expression and activity while increasing small heterodimer partner expression and its recruitment to the CYP2D6 promoter. The genotypes are key determinants of interindividual variability in CYP2D6 expression and activity. Recent genome-wide association studies have identified a large number of genes that can regulate CYP2D6. Pregnancy induces CYP2D6 via unknown mechanisms. Renal or liver diseases, smoking and alcohol use have minor to moderate effects only on CYP2D6 activity. Unlike CYP1 and 3 and other CYP2 members, CYP2D6 is resistant to typical inducers such as rifampin, phenobarbital and dexamethasone. Post-translational modifications such as phosphorylation of CYP2D6 Ser135 have been observed, but the functional impact is unknown. Further functional and validation studies are needed to clarify the role of nuclear receptors, epigenetic factors and other factors in the regulation of CYP2D6.

Transitioning from Idiopathic to Explainable Autoimmune Hepatitis

Autoimmune hepatitis lacks an identifiable cause, and its diagnosis requires the exclusion of etiologically defined diseases that resemble it. Insights into its pathogenesis are moving autoimmune hepatitis from an idiopathic to explainable disease, and the goal of this review is to describe the insights that are hastening this transition. Two types of autoimmune hepatitis are justified by serological markers, but they also have distinctive genetic associations (DRB1 and DQB1 genes) and autoantigens. DRB1 alleles are the principal susceptibility factors in white adults, and a six amino acid sequence encoded in the antigen-binding groove of class II molecules of the major histocompatibility complex can influence the selection of autoantigens. Polymorphisms, including variants of SH2B3 and CARD10 genes, may affect immune reactivity and disease severity. The cytochrome mono-oxygenase, CYP2D6, is the autoantigen associated with type 2 autoimmune hepatitis, and it shares homologies with multiple viruses that might promote self-intolerance by molecular mimicry. Chemokines, especially CXCL9 and CXCL10, orchestrate the migration of effector cells to sites of injury and are associated with disease severity. Cells of the innate and adaptive immune responses promote tissue damage, and possible deficiencies in the number and function of regulatory T cells may facilitate the injurious process. Receptor-mediated apoptosis is the principal mechanism of hepatocyte loss, and cell-mediated and antibody-dependent mechanisms of cytotoxicity also contribute. Insights that explain autoimmune hepatitis will allow triggering exogenous antigens to be characterized, risk management to be improved, prognostic indices to be refined, and site-specific therapeutic interventions to emerge.

Serological markers of autoimmunity in children with hepatitis A: relation to acute and fulminant presentation

OBJECTIVES

Hepatitis A virus (HAV) infection tends to be a self-limiting disease without serious sequelae, but fulminant hepatitis, with a high mortality, develops in 0.1-0.2% of the cases. Sometimes, HAV infection precipitates autoimmune hepatitis (AIH). We aimed to assess the frequency and clinical significance of serologic markers of autoimmunity during hepatitis A infection with an acute or fulminant presentation compared with those in AIH.

METHODS

The study included 126 children: 46 with HAV infection (33 with acute and 13 with fulminant presentation), 53 with AIH, and 27 healthy controls. In all, we measured autoantibodies titer (antinuclear antibody, antismooth muscle antibody, and liver kidney microsomal antibody-1) and serum gammaglobulins.

RESULTS

Autoantibodies were detected in the majority of HAV (63.1%) and AIH (79.2%) groups, but in none of the controls. Gammaglobulins were significantly higher in the HAV group (1.93±0.57 g/dl) than in the controls (1.32±0.29 g/dl), but lower than that in the AIH group (2.93±1.2 g/dl) (P<0.0001 for all). In the HAV group, gammaglobulins were significantly higher in those with fulminant (2.21±0.46 g/dl) than in those with acute presentation (1.82±0.57 g/dl) (P=0.019), but comparable with that in AIH (P=0.095). Gammaglobulins correlated significantly with disease severity in both HAV and AIH groups.

CONCLUSION

Hypergammaglobulinemia and a high occurrence of autoantibodies are encountered in HAV infection. This may support the immunological basis of its pathogenesis. Moreover, the higher gammaglobulins in fulminant HAV, with an insignificant difference from that in AIH, suggest that a more aggressive immunological reaction is related to this presentation.

Regulatory T cells: Mechanisms of suppression and impairment in autoimmune liver disease

There are three classic liver diseases with probable autoimmune etiology: primary biliary cirrhosis, primary sclerosing cholangitis, and autoimmune hepatitis. The occurrence of these autoimmune conditions is determined by the breakdown of immune-regulatory mechanisms that in health are responsible for maintaining immunological tolerance against self-antigens. Among the multiple T cell subsets with suppressive function, the regulatory T cells (Tregs), defined by the expression of CD4, the IL-2 receptor α chain (CD25), and the transcription factor FOXP3, have emerged as having a central role in maintaining immune-tolerance to autoantigens. Tregs are equipped with an array of mechanisms of suppression, including the modulation of antigen presenting cell maturation and function, the killing of target cells, the disruption of metabolic pathways, and the production of anti-inflammatory cytokines. In all the three autoimmune liver diseases mentioned above, there is evidence pointing for either a reduced frequency and/or function of Tregs. Here, we review the definition, phenotypic characteristics, and mechanisms of suppression employed by Tregs and then we discuss the evidence available pointing to their impairment in patients with autoimmune liver disease.

Autoimmune hepatitis, one disease with many faces: Etiopathogenetic, clinico-laboratory and histological characteristics

Autoimmune hepatitis (AIH) is an unresolving progressive liver disease of unknown etiology characterized by hypergammaglobulinemia, autoantibodies detection and interface hepatitis. Due to the absence of specific diagnostic markers and the large heterogeneity of its clinical, laboratory and histological features, AIH diagnosis may be potentially difficult. Therefore, in this in-depth review we summarize the substantial progress on etiopathogenesis, clinical, serological and histological phenotypes of AIH. AIH has a global distribution affecting any age, both sexes and all ethnic groups. Clinical manifestations vary from asymptomatic to severe or rarely fulminant hepatitis. Hypergammaglobulinemia with selective elevation of IgG is found in most cases. Autoimmune attack is perpetuated, possibly via molecular mimicry, and favored by the impaired control of T-regulatory cells. Histology (interface hepatitis, emperipolesis and hepatic rosette formation) and autoantibodies detection although not pathognomonic, are still the hallmark for a timely diagnosis. AIH remains a major diagnostic challenge. AIH should be considered in every case in the absence of viral, metabolic, genetic and toxic etiology of chronic or acute hepatitis. Laboratory personnel, hepato-pathologists and clinicians need to become more familiar with disease expressions and the interpretation of liver histology and autoimmune serology to derive maximum benefit for the patient.

Autoimmune hepatitis: a classic autoimmune liver disease

AIH is characterized by chronic inflammation of the liver, interface hepatitis, hypergammaglobulinemia, and production of autoantibodies. Based on the nature of the serum autoantibodies, two types of AIH are recognized: type 1 (AIH-1), positive for ANA and/or anti-smooth muscle antibody, and type 2 (AIH-2), defined by the positivity for anti-liver kidney microsomal type 1 antibody or for anti-liver cytosol type 1 antibody. AIH demonstrates a female preponderance with the female-to-male ratio of 4:1 in AIH-1 and 10:1 in AIH-2. Several genes confer susceptibility to AIH and influence clinical manifestation, response to treatment, and overall prognosis. Most are located within the human leukocyte antigen (HLA) region, which is involved in the presentation of antigenic peptides to T cells and thus in the initiation of adaptive immune responses. The strongest associations are found within the HLA-DRB1 locus. In patients with increased genetic susceptibility to AIH, immune responses to liver autoantigens could be triggered by molecular mimicry. Because of molecular mimicry, different environmental agents, drugs, and viruses might produce AIH. In AIH, T cells are numerically and functionally impaired, permitting the perpetuation of effector immune responses with ensuing persistent liver destruction. AIH is rare but highly treatable inflammatory condition of the liver. Subclinical and asymptomatic disease is common. AIH therefore needs to be considered in the differential diagnosis of all patients with elevated liver enzymes. Clinical response to immunosuppressive therapy is characteristic and supports the diagnosis.

CYP2E1 autoantibodies in liver diseases

Autoimmune reactions involving cytochrome P4502E1 (CYP2E1) are a feature of idiosyncratic liver injury induced by halogenated hydrocarbons and isoniazid, but are also detectable in about one third of the patients with advanced alcoholic liver disease (ALD) and chronic hepatitis C (CHC). In these latter the presence of anti-CYP2E1 auto-antibodies is an independent predictor of extensive necro-inflammation and fibrosis and worsens the recurrence of hepatitis following liver transplantation, indicating that CYP2E1-directed autoimmunity can contribute to hepatic injury. The molecular characterization of the antigens recognized by anti-CYP2E1 auto-antibodies in ALD and CHC has shown that the targeted conformational epitopes are located in close proximity on the molecular surface. Furthermore, these epitopes can be recognized on CYP2E1 expressed on hepatocyte plasma membranes where they can trigger antibody-mediated cytotoxicity. This does not exclude that T cell-mediated responses against CYP2E1 might also be involved in causing hepatocyte damage. CYP2E1 structural modifications by reactive metabolites and molecular mimicry represent important factors in the breaking of self-tolerance against CYP2E1 in, respectively, ALD and CHC. However, genetic or acquired interferences with the mechanisms controlling the homeostasis of the immune system are also likely to contribute. More studies are needed to better characterize the impact of anti-CYP2E1 autoimmunity in liver diseases particularly in relation to the fact that common metabolic alterations such as obesity and diabetes stimulates hepatic CYP2E1 expression.

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CYP2E1 is a frequent autoimmune target in alcoholic liver disease and hepatitis C.

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Anti-CYP2E1 auto-antibodies mainly target conformational epitopes.

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Molecular mimicry contribute to anti-CYP2E1 autoimmunity during HCV infection.

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Anti-CYP2E1 autoimmunity contributes to the evolution of liver damage.

Mechanisms of tissue injury in autoimmune liver diseases

Autoimmune diseases affecting the liver are mainly represented by autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC). The characteristic morphologic patterns of injury are a chronic hepatitis pattern of damage in AIH, destruction of small intrahepatic bile ducts in PBC and periductal fibrosis and inflammation involving larger bile ducts in PSC. The factors responsible for initiation and perpetuation of the injury in all the three autoimmune liver diseases are not understood completely but are likely to be environmental triggers on the background of genetic variation in immune regulation. In this review, we summarise the current understanding of the mechanisms underlying the breakdown of self-tolerance in autoimmune liver diseases.

Review article: permanent drug withdrawal is desirable and achievable for autoimmune hepatitis

BACKGROUND

Autoimmune hepatitis can be rendered treatment-free, but the difficulty, frequency and risks associated with the pursuit of this outcome are unclear.

AIM

To describe the frequency that autoimmune hepatitis can be rendered treatment-free, identify the features that characterise these patients, examine the pathogenic pathways that may sustain or terminate the disease and indicate management protocols that can obtain this result.

METHODS

Studies cited in Pub Med from 1972-2014 for autoimmune hepatitis, treatment, relapse, remission and outcome were selected.

RESULTS

The frequency of a treatment-free state varies from 19% to 40% in patients observed for ≥3 years after drug withdrawal. Complete laboratory resolution and reversion to normal liver tissue prior to drug withdrawal favours this response. The development of cirrhosis during therapy may increase treatment-dependence. Persistent liver damage and the generation of neo-antigens during the apoptosis of hepatocytes may perpetuate the disease. Genetic and age-related effects on the vigour of the immune response may also contribute. Reversion to normal liver tissue is achieved in only 22% of patients during conventional corticosteroid therapy, and the emerging pharmacological and biological interventions may improve this frequency. A management strategy designed to achieve a treatment-free state accommodates all candidates for this outcome, and it can be modified to a long-term maintenance strategy as warranted by the clinical response.

CONCLUSIONS

Permanent drug withdrawal is a treatment outcome that is desirable and achievable in patients with autoimmune hepatitis. Normalisation of liver tests and liver tissue during treatment enhances this occurrence.

Liver immunology

The liver is the largest organ in the body and is generally regarded by nonimmunologists as having little or no lymphoid function. However, such is far from accurate. This review highlights the importance of the liver as a lymphoid organ. Firstly, we discuss experimental data surrounding the role of liver as a lymphoid organ. The liver facilitates tolerance rather than immunoreactivity, which protects the host from antigenic overload of dietary components and drugs derived from the gut and it is instrumental to fetal immune tolerance. Loss of liver tolerance leads to autoaggressive phenomena, which if not controlled by regulatory lymphoid populations, may lead to the induction of autoimmune liver diseases. Liver-related lymphoid subpopulations also act as critical antigen-presenting cells. The study of the immunological properties of liver and delineation of the microenvironment of the intrahepatic milieu in normal and diseased livers provides a platform to understand the hierarchy of a series of detrimental events that lead to immune-mediated destruction of the liver and the rejection of liver allografts. The majority of emphasis within this review will be on the normal mononuclear cell composition of the liver. However, within this context, we will discuss selected, but not all, immune-mediated liver disease and attempt to place these data in the context of human autoimmunity.

Autoimmune hepatitis

Autoimmune hepatitis is a disease of the hepatic parenchyma that can present in acute or chronic forms. In common with many autoimmune diseases, autoimmune hepatitis is associated with non-organ-specific antibodies in the context of hepatic autoimmunity. This dichotomy has made definition of a unifying hypothesis in the pathophysiology of the disease difficult, although data from the past 8 years have drawn attention to the role of regulatory T cells. Several triggers have been identified, and the disease arises in genetically susceptible individuals. Clinical and biochemical remission is achievable in up to 85% of cases. For the remaining patients, alternative immunosuppression strategies are an option. Liver transplantation provides an excellent outcome for patients with acute liver failure or complications of end-stage liver disease, including hepatocellular carcinoma. Variant or overlapping syndromes are worthy of consideration when unexpected disease features arise.

Review article: autoimmune hepatitis -- current management and challenges

BACKGROUND

Autoimmune hepatitis (AIH) is a disease of unknown aetiology characterised by interface hepatitis, hypergammaglobulinaemia, circulating autoantibodies and a favourable response to immunosuppression.

AIM

To review recent advancements in understanding aetiopathogenesis, clinical, serological and histological features, diagnostic criteria and treatment strategies of AIH.

METHODS

Published studies on AIH extracted mainly from PubMed during the last 15 years.

RESULTS

Autoimmune hepatitis has a global distribution affecting any age, both sexes and all ethnic groups. Clinical manifestations are variable ranging from no symptoms to severe acute hepatitis and only seldom to fulminant hepatic failure. Autoimmune attack is perpetuated, possibly via molecular mimicry mechanisms, and favoured by the impaired control of regulatory T-cells. A typical laboratory finding is hypergammaglobulinaemia with selective elevation of IgG, although in 15-25% of patients - particularly children, elderly and acute cases - IgG levels are normal. Liver histology and autoantibodies, although not pathognomonic, still remain the hallmark for diagnosis. Immunosuppressive treatment is mandatory and life-saving; however, to meet strict response criteria, the conventional therapy with prednisolone with or without azathioprine is far from ideal.

CONCLUSIONS

Autoimmune hepatitis remains a major diagnostic and therapeutic challenge. The clinician, the hepato-pathologist and the laboratory personnel need to become more familiar with different expressions of the disease, interpretation of liver histology and autoimmune serology. According to the strict definition of treatment response issued by the 2010 AASLD guidelines, many patients are nonresponders to conventional treatment. Newer immunosuppressive agents targeting pathogenetic mechanisms can improve patient management, which needs to be tailored on a case-by-case basis.