Autoimmune hepatitis.

Autoimmune hepatitis is an inflammatory liver disease in which the immune system is believed to orchestrate an immune attack onto the liver cell. Current knowledge suggests that both T helper 1 (TH1) and TH2 programmes are involved in the generation of the liver damage. Release of TH2 cytokines leads to the production of autoantibodies to the hepatocyte membrane that recruit killer cells. TH1 cytokines induce macrophage activation which contributes to hepatocyte destruction. Patients commonly possess the "autoimmune" HLA A1/B8/DR3 haplotype and a silent gene at the C4A locus with consequent partial deficiency of the complement component C4. Two main types of autoimmune hepatitis are recognised according to the presence of circulating non-organ specific autoantibodies. Patients with smooth muscle antibody and/or antinuclear antibody may be adults or children, while patients with antiliver kidney microsomal type 1 (LKM1) antibody are usually children or very young adults. In both types there is a preponderance of females. LKM1 antibody is also present in a proportion of adult patients, mainly male, with chronic hepatitis C virus infection. This observation originally led to the suggestion that hepatitis C virus may be the cause of this form of autoimmune hepatitis, but several studies have shown that the epitopes target of the LKM1 antibody in autoimmune hepatitis and chronic hepatitis C virus infection differ. Although autoimmune hepatitis responds satisfactorily to immunosuppression in the short term, progression to cirrhosis is frequent. It is hoped that ongoing research will provide a better understanding of the pathogenic mechanisms of liver damage leading to a more effective and specific mode of treatment.