Journal of Autoimmune Disorders

Description

Autoimmune hepatitis is generally characterized by a mononuclear-cell infiltrate invading the limiting plate that is, the sharply demarcated hepatocyte boundary that surrounds the portal triad and permeates the surrounding parenchyma (periportal infiltrate, also called piecemeal necrosis or interface hepatitis that progresses to lobular hepatitis). There may be an abundance of plasma cells, a finding that in the past led to the use of the term “plasma-cell hepatitis.” Eosinophils are frequently present. The portal lesion generally spares the biliary tree. Fibrosis is present in all but the mildest forms of autoimmune hepatitis. In advanced disease, the fibrosis is extensive, and with the distortion of the hepatic lobule and the appearance of regenerative nodules, it results in cirrhosis. Occasionally, centrizonal lesions occur.
The findings in patients with acute-onset autoimmune hepatitis differ somewhat from those with an insidious presentation. Patients presenting with fulminant hepatic failure tend to have interface and lobular hepatitis, lobular disarray, and hepatocyte, central, and submassive necrosis. However, they have less fibrosis than patients who present with a more chronic course. Steatosis occurs in a minority of patients, although nonalcoholic fatty liver disease may occur in conjunction with autoimmune hepatitis. The various histologic appearances in patients who have a spontaneous or pharmacologically induced remission, the histologic findings may revert to normal or inflammation may be confined to portal areas. In this setting, cirrhosis may become inactive and fibrosis may diminish or disappear although we have long known that the clinical, histologic, and serologic profiles of so-called overlap, mixed, or variant syndromes differ from the classic features of autoimmune hepatitis, primary biliary cirrhosis, and primary sclerosing cholangitis, no consensus regarding categorization has been reached. Terms such as “overlap syndrome,” “antimitochondrial-antibody–negative primary biliary cirrhosis,” “the hepatic form of primary biliary cirrhosis,” “autoimmune cholangitis,” “autoimmune cholangiopathy,” “chronic autoimmune cholestasis,” “immunocholangitis,” “immune cholangiopathy,” and “combined hepatitic/cholestatic syndrome” have all been used to describe patients with features of both autoimmune hepatitis and primary biliary cirrhosis. The presentation of putative coincidental diseases, consecutive diseases, and evolution from one disease to another have highlighted the complexity of this issue.

Autoimmune Disease and Autoantibodies

Most mouse studies are limited by the absence of predisposing genetic alterations that lead to autoimmune hepatitis and development of an acute rather than chronic (relapsing) hepatitis. Furthermore, the use of infective triggers coupled with little autoantibody formation in association with the hepatic process restricts their applicability. In the Concanavalin A (Con A) model, mice present with acute liver failure and a dose-dependent increase in aspartate aminotransferase (AST) within 8 h of the injection with Con A, although histopathological lesions of autoimmune hepatitis are not common. Gorham and colleagues developed a mouse model by backcrossing mice defi cient in transforming growth factor β with the BALB/c background; these animals developed lethal hepatitis with an ALT increase. Kido and colleagues38 produced a mouse model of spontaneous autoimmune hepatitis by inducing concurrent loss of two controlling mechanisms: FOXP3pos regulatory T cells and PD1-mediated signalling. After neonatal thymectomy to substantially reduce the number of FOXP3pos regulatory T cells mice develop fatal autoimmune hepatitis characterised by severe T lymphocyte infi ltration and increased titres of antinuclear antibodies. Importantly, adoptive transfer of regulatory T cells can suppress the progression of fatal hepatitis after initiation of autoimmune hepatitis, confi rming both the role of autoreactive T lymphocytes in liver damage and that of regulatory T cells in tolerance. By contrast with these studies that emphasise the importance of breakdown of immune tolerance in induction and progression of autoimmune hepatitis, work to develop a mouse model of type 2 disease is in progress, in which the autoantigen CYP2D6 has been identifi ed and characterised in detail. Lapierre and colleagues findings.
Autoimmune hepatitis (AIH) is a generally unresolving inflammation of the liver of unknown cause. A working model for its pathogenesis postulates that environmental triggers, a failure of immune tolerance mechanisms, and a genetic predisposition collaborate to induce a T cell–mediated immune attack upon liver antigens, leading to a progressive necroinflammatory and fibrotic process in the liver. Onset is frequently insidious with nonspecific symptoms such as fatigue, jaundice, nausea, abdominal pain, and arthralgias at presentation, but the clinical spectrum is wide, ranging from an asymptomatic presentation to an acute severe disease. The diagnosis is based on histologic abnormalities, characteristic clinical and laboratory findings, abnormal levels of serum globulins, and the presence of one or more characteristic autoantibodies.

Immunosuppressive Treatment

Several environmental agents, such as viruses, have been suggested as putative triggers for autoimmune hepatitis. The suggestion of molecular mimicry and crossreactivity between epitopes of viruses, drugs, and hepatic antigens is attractive, and viral antigens or triggers might need to hit several times to activate a fi nal common pathway. In that situation, priming of the immune system could occur years before the develop ment of overt disease, and the identifi cation of a triggering virus or drug is rarely possible. So far, several viruses have been associated with the development of autoimmune hepatitis, such as hepatitis A, hepatitis C hepatitis E measles Epstein-Barr and herpes simplex viruses. In add ition to viruses, research has identifi ed several agents that precipitate autoimmune hepatitis, such as minocycline, tienilic acid nitrofurantoin pemoline melatonin ornidazole diclofenac propylthiouracil and statins.  Herbal remedies, such as dai-taiko-so (da chai hu tang; commonly used in Japan), have also been associated with the disorder.
Liver biopsy examination at presentation is recommended to establish the diagnosis and to guide the treatment decision. In acute presentation unavailability of liver biopsy should not prevent from start of therapy. Interface hepatitis is the histological hallmark and plasma cell infiltration is typical. Neither histological finding is specific for AIH, and the absence of plasma cells in the infiltrate does not preclude the diagnosis. Eosinophils, lobular inflammation, bridging necrosis, and multiacinar necrosis may be present. Granulomas rarely occur. The portal lesions generally spare the bile ducts. In all but the mildest forms, fibrosis is present and, with advanced disease, bridging fibrosis or cirrhosis is seen. Occasionally, centrizonal (zone 3) lesions exist  and sequential liver tissue examinations have demonstrated transition of this pattern to interface hepatitis in some patients. The histological findings differ depending on the kinetics of the disease. Compared to patients with an insidious