Autoimmune hepatitis as a unique form of an autoimmune liver disease: immunological aspects and clinical overview

Selected transgenic murine models of human autoimmune liver diseases

Murine models of human diseases are of outmost importance for both studying molecular mechanisms driving their development and testing new treatment strategies. In this review, we first discuss the etiology and risk factors for autoimmune liver disease, including primary biliary cholangitis, autoimmune hepatitis and primary sclerosing cholangitis. Second, we highlight important features of murine transgenic models that make them useful for basic scientists, drug developers and clinical researchers. Next, a brief description of each disease is followed by the characterization of selected animal models.

Rescue of autoimmune hepatitis by soluble MHC class II molecules in an altered concanavalin A-induced experimental model

BACKGROUND

Soluble major histocompatibility complex class II (sMHCII) molecules have been described to maintain tolerance through the suppression of autoreactive T lymphocytes. In order to evaluate their ability to rescue autoimmune hepatitis (AIH) symptoms, the present work attempted to administer sMHCII molecules to an in vitro as well as in vivo concanavalin A (ConA)-induced AIH model.

METHODS

The in vitro AIH model consisted of splenocyte stimulation with ConA in the presence or absence of serum-isolated sMHCII molecules. An in vivo ConA-modified model with or without sMHCII treatment was developed. The cytokine profile in culture supernatants and serum was tested by ELISA. Cell markers were evaluated by immunofluorescence, while cell proliferation by tritiated thymidine uptake. AIH symptoms were assessed by daily observations for the establishment of a disease severity scoring system and liver histology was evaluated using a biomolecular imager.

RESULTS

The presence of sMHCII molecules in the ConA-stimulated cell cultures leads to a significant reduction of cell proliferation. The administration of sMHCII molecules to the ConA-treated animals showed a significant reduction in the levels of IL-2, IL-4, and IL-10, as well as a decrease in the number of spleen CD4+ and CD8+ cells. Upon development of a scoring system, it was shown that the sMHCII treatment was accompanied by a slower progression of the disease, while rescuing fibrotic liver morphology.

CONCLUSION

The results presented in this study confirm the ability of sMHCII proteins to alleviate autoimmune hepatitis, possibly highlighting new therapeutic approaches for autoimmune diseases.

"Let my liver rather heat with wine" - a review of hepatic fibrosis pathophysiology and emerging therapeutics

Cirrhosis is characterized by extensive hepatic fibrosis, and it is the 14th leading cause of death worldwide. Numerous contributing conditions have been implicated in its development, including infectious etiologies, medication overdose or adverse effects, ingestible toxins, autoimmunity, hemochromatosis, Wilson’s disease and primary biliary cholangitis to list a few. It is associated with portal hypertension and its stigmata (varices, ascites, hepatic encephalopathy, combined coagulopathy and thrombophilia), and it is a major risk factor for hepatocellular carcinoma. Currently, orthotopic liver transplantation has been the only curative modality to treat cirrhosis, and the scarcity of donors results in many people waiting years for a transplant. Identification of novel targets for pharmacologic therapy through elucidation of key mechanistic components to induce fibrosis reversal is the subject of intense research. Development of robust models of hepatic fibrosis to faithfully characterize the interplay between activated hepatic stellate cells (the principal fibrogenic contributor to fibrosis initiation and perpetuation), hepatocytes and extracellular matrix components has the potential to identify critical components and mechanisms that can be exploited for targeted treatment. In this review, we will highlight key cellular pathways involved in the pathophysiology of fibrosis from extracellular ligands, effectors and receptors, to nuclear receptors, epigenetic mechanisms, energy homeostasis and cytokines. Further, molecular pathways of hepatic stellate cell deactivation are discussed, including apoptosis, senescence and reversal or transdifferentiation to an inactivated state resembling quiescence. Lastly, clinical evidence of fibrosis reversal induced by biologics and small molecules is summarized, current compounds under clinical trials are described and efforts for treatment of hepatic fibrosis with mesenchymal stem cells are highlighted. An enhanced understanding of the rich tapestry of cellular processes identified in the initiation, perpetuation and resolution of hepatic fibrosis, driven principally through phenotypic switching of hepatic stellate cells, should lead to a breakthrough in potential therapeutic modalities.

Complications of Cirrhosis in Primary Care: Recognition and Management of Hepatic Encephalopathy

Approximately 3.7% of patients in primary care settings have chronic liver disease, and 18% with chronic liver disease in the specialty care setting have cirrhosis. For cirrhotic patients without complications, prognosis is generally favorable; increased morbidity and mortality are observed when complications (i.e., hepatic encephalopathy [HE]) occur. HE occurs in up to 70% of patients with cirrhosis. Neurologic signs in HE span a wide spectrum, from those not easily apparent (covert) to more clinically obvious signs (overt). Providers should consider overt HE in patients with cirrhosis and signs of impaired cognition, confusion, consciousness and/or personality changes, and/or impaired memory. Overt HE treatment includes identifying and treating precipitating factors and reducing bacterial-derived toxin loads. For acute overt HE, lactulose is first-line treatment. To prevent HE recurrence, lactulose plus rifaximin is recommended. Patients with cirrhosis and HE often present in primary care; recognizing and properly managing HE are important in this setting.

Translocation of a gut pathobiont drives autoimmunity in mice and humans

Despite multiple associations between the microbiota and immune diseases, their role in autoimmunity is poorly understood. We found that translocation of a gut pathobiont, Enterococcus gallinarum, to the liver and other systemic tissues triggers autoimmune responses in a genetic background predisposing to autoimmunity. Antibiotic treatment prevented mortality in this model, suppressed growth of E. gallinarum in tissues, and eliminated pathogenic autoantibodies and T cells. Hepatocyte-E. gallinarum cocultures induced autoimmune-promoting factors. Pathobiont translocation in monocolonized and autoimmune-prone mice induced autoantibodies and caused mortality, which could be prevented by an intramuscular vaccine targeting the pathobiont. E. gallinarum-specific DNA was recovered from liver biopsies of autoimmune patients, and cocultures with human hepatocytes replicated the murine findings; hence, similar processes apparently occur in susceptible humans. These discoveries show that a gut pathobiont can translocate and promote autoimmunity in genetically predisposed hosts.

Autoimmune Hepatitis in Hawai'i

Autoimmune Hepatitis (AIH) is a poorly understood disease. There has been a paucity of reports on the epidemiology and clinical course of AIH in multiethnic populations. The aim of this study is to examine the clinical and serologic features of AIH in the multiethnic population of Hawai'i. This was a retrospective, cross-sectional study of a cohort of patients seen between 2010-2013 in a tertiary referral center in Hawai'i. All 32 patients were diagnosed according to International Autoimmune Hepatitis Group (IAIHG) criteria. The mean (SD) age of diagnosis was 49.4 (17.5) years, 75% of patients were female, 72% were Asian, 19% were Caucasian, 6% were Pacific Islander, and 3% were African American. When compared to Caucasians, Asians had lower transaminase levels and international normalized ratio (INR), and were more likely to have anti-nuclear antibody (ANA) seropositivity at presentation. Asians were also older at diagnosis and more likely to achieve complete or partial remission. Patients diagnosed before the age of 40 had higher levels of total bilirubin at presentation compared to those diagnosed after the age of 40. No significant differences were observed between genders. Asian patients with type I AIH present later in life with more favorable laboratory values, and have a superior treatment response compared to Caucasians. Diagnosis before the age of 40 is associated with less favorable laboratory values at diagnosis. Further studies are necessary to validate these findings and determine the reason for the ethnic differences.

Autoimmune Hepatitis: Clinical Review with Insights into the Purinergic Mechanism of Disease

Autoimmune hepatitis (AIH) is an important disorder that predominantly results in inflammatory liver disease in genetically predisposed women. The clinicopathological picture is characterized by symptoms associated with both systemic inflammation and hepatic dysfunction, and with increased serum aminotransferases, elevated IgG, autoantibodies, and interface hepatitis on liver biopsy. AIH usually results in liver injury as a consequence of chronic hepatitis and cirrhosis. However, rarely, patients may present with fulminant liver failure. Early diagnosis is important in all instances because the disease can be highly responsive to immunosuppressive therapeutic options. Left untreated, the disease is associated with high morbidity and mortality. Here we provide an overview of the current state of knowledge on AIH and summarize the treatment options for this serious condition in adults. We also discuss the pathogenesis of the disease as a possible consequence of autoimmunity and the breakdown of hepatic tolerance. We focus on regulatory T cell impairments as a consequence of changes in CD39 ectonucleotidase expression and altered purinergic signaling. Further understanding of hepatic tolerance may aid in the development of specific and well-tolerated therapies for AIH.

Autoimmune hepatitis in childhood: The role of genetic and immune factors

Autoimmune hepatitis (AIH) is a rare chronic inflammatory disease of the liver, which affects a group of patients who lost their immunological tolerance to antigens of the liver. It is clinically characterized by hypergammaglobulinemia, elevated liver enzymes, presence of autoantibodies and histological changes. Although being rare in children, it represents a serious cause of chronic hepatic disease that can lead to cirrhosis and hepatic failure. Clinical findings, exclusion of more common liver disorders and the detection of antibodies antinuclear antibodies, smooth muscle antibodies and anti-LKM1 are usually enough for diagnosis on clinical practice. The pathogenic mechanisms that lead to AIH remain obscure, but some research findings suggest the participation of immunologic and genetic factors. It is not yet knew the triggering factor or factors that stimulate inflammatory response. Several mechanisms proposed partially explain the immunologic findings of AIH. The knowledge of immune factors evolved might result in better markers of prognosis and response to treatment. In this review, we aim to evaluate the findings of research about genetic and immune markers and their perspectives of application in clinical practice especially in pediatric population.