John M. Vierling M.D. is Professor of Medicine and Surgery at the Baylor College of Medicine in Houston, Texas, where he also serves as Director of Baylor Liver Health and Chief of Hepatology. In addition, he is the Director of Advanced Liver Therapies, a center devoted to clinical research in hepatobiliary diseases at St. Luke's Episcopal Hospital. Dr. Vierling is board certified in internal medicine and gastroenterology and a Fellow of the American College of Physicians.
Dr. Schoenfield served as associate professor of medicine and consultant in gastroenterology on the faculty of the Mayo Clinic for seven years. He became a professor of medicine in residence at UCLA from 1972 to 1999 (now emeritus). He was the director of gastroenterology at Cedars-Sinai Medical Center in Los Angeles for 25 years, where he received the chief resident's teaching award, the president's award, and the pioneer of medicine award.
Between 95 and 98% of patients with primary biliary cirrhosis (PBC) have autoantibodies (antibodies to self) in their blood that react with the inner lining of mitochondria. These autoantibodies are called antimitochondrial antibodies (AMA). Mitochondria are the energy factories present inside all of our cells, not just the cells of the liver or bile ducts. (The mitochondria use the oxygen carried in the blood from the lungs as a fuel to generate energy.) AMA actually bind to protein antigens that are contained in multienzyme complexes (packages of enzymes) within the inner lining of the mitochondria. These multienzyme complexes produce key chemical reactions necessary for life. The complexes are referred to as multienzyme because they are made up of multiple enzyme units.
AMA specifically react against a component of this multienzyme complex called E2. In PBC, AMA preferentially react with the E2 component of one of the multienzymes that is called the pyruvate dehydrogenase complex (PDC). Accordingly, the antigen is designated as PDC-E2. The practical importance of all of this is that the PDC-E2 antigen is now used, as discussed below, in a diagnostic test for PBC. The PDC-E2 antigen is also referred to as M2, a term introduced to designate it as the second mitochondrial antigen discovered by researchers interested in PBC.