Antibody

Hepatitis

Azathioprine

Transplantation

Immune system

Prednisolone

Disease

Prednisone

Immunosuppression

Internal medicine

Liver disease

Autoimmune hepatitis

Autoantibody

Immunology

Liver transplantation

Medicine

Nature Reviews Disease Primers

Autoimmune hepatitis (AIH) is a severe liver disease that affects children and adults worldwide. The diagnosis of AIH relies on increased serum transaminase and immunoglobulin G levels, presence of autoantibodies and interface hepatitis on liver histology. AIH arises in genetically predisposed individuals when a trigger, such as exposure to a virus, leads to a T cell-mediated autoimmune response directed against liver autoantigens; this immune response is permitted by inadequate regulatory immune control leading to a loss of tolerance. AIH responds favourably to immunosuppressive treatment, which should be started as soon as the diagnosis is made. Standard regimens include fairly high initial doses of corticosteroids (prednisone or prednisolone), which are tapered gradually as azathioprine is introduced. For those patients who do not respond to standard treatment, second-line drugs should be considered, including mycophenolate mofetil, calcineurin inhibitors, mechanistic target of rapamycin (mTOR) inhibitors and biologic agents, which should be administered only in specialized hepatology centres. Liver transplantation is a life-saving option for those who progress to end-stage liver disease, although AIH can recur or develop de novo after transplantation. In-depth investigation of immune pathways and analysis of changes to the intestinal microbiota should advance our knowledge of the pathogenesis of AIH and lead to novel, tailored and better tolerated therapies. Autoimmune hepatitis (AIH) is a severe liver disease in which loss of tolerance against the patient's own liver antigens, probably triggered by environmental agents, occurs in genetically susceptible individuals. This Primer explores the current understanding of AIH and outlines future research priorities.