Antimitochondrial antibody screening
Test for primary biliary cirrhosis diagnosis.
Antibodies to mitochondria are found in patients with primary biliary cirrhosis (PBC). Antibodies to mitochondria are a family of antimitochondrial antibodies directed against a number of oxidative phosphorylation enzymes of the inner mitochondrial membrane. There are 9 varieties of antimitochondrial antibodies. M2, M4, M8 and M9 can be considered as specific markers of primary biliary cirrhosis. Mitochondria are small organelles within cells which main function is the exchange of energy substrates, metabolism of carbohydrates and fats.
In primary biliary cirrhosis, the leading autoantibody antigen (AMA-M2) is the E2 subunit of the 2-oxodehydrogenase complex, which is involved in the tricarboxylic acid cycle and fatty acid synthesis. The pyruvate-decarboxylase complex performs lipid cleavage and is susceptible to many hepatotoxic substances. Modification of its antigenic components probably plays a leading role in the development of the autoimmune response in PBC. At the same time, the role of antimitochondrial antibodies in the pathogenesis of the disease has not been established, as the immunization of laboratory animals with the antigen does not lead to the development of PBC.
Antibodies to mitochondria are found in 80-90% of patients with primary biliary cirrhosis. Antibodies to mitochondria can be detected up to 10 years before the clinical debut of the disease. The detection of antibodies in other rheumatic diseases, such as Sjogren's syndrome or scleroderma, indicates an increased risk of developing primary biliary cirrhosis in these conditions. Antibodies to mitochondria are noted in 1-5% of patients with autoimmune hepatitis of type 1, which allows the diagnosis of a crossover syndrome combining autoimmune hepatitis and primary biliary cirrhosis. Antimitochondrial antibody titers do not change with therapy and may persist after liver transplantation.
There are other characteristic changes in laboratory parameters: increased bilirubin, alkaline phosphatase, gamma-glutamate transpeptidase, hypercholesterolemia, hypergammaglobulinemia, mainly due to IgM immunoglobulin.