The pyruvate dehydrogenase complex as a target autoantigen in primary biliary cirrhosis.

Mitochondrial autoantigens and their B and T cell autoepitopes have been well defined in primary biliary cirrhosis (PBC). However, the relationships of the antimitochondrial antibodies and the mechanisms of bile duct destruction in PBC remain an enigma. The serological hallmark of PBC remains the presence of antibodies to mitochondria, particularly to the E2 component of the pyruvate dehydrogenase complex (PDC-E2). However, several mechanisms may now be proposed which may explain the immune-mediated bile duct damage in PBC. These include the possible role of T cell-mediated cytotoxicity as well as the interaction between the IgA class of antimitochondrial antibodies and the mitochondrial autoantigens. A prominent feature in this discussion is the highly directed and specific immune response to the mitochondrial antigens, including PDC-E2 as well as other members of the 2-oxo-acid dehydrogenase complexes. Ultimately, the mechanisms that lead to this immune reaction should provide data on other questions in PBC, including the reasons for female predominance, the absence of PBC in children and the relative ineffectiveness of immunosuppressive agents.