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Antimitochondrial antibodies in serum
Last reviewed: 23.04.2024
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Antimitochondrial antibodies (AMA) by indirect immunofluorescence in serum are not normally determined; when using ELISA, normal values are less than 20 IU / ml; 20-25 IU / ml - boundary values.
Antimitochondrial antibodies are produced to antigens of the inner mitochondrial membrane. Antigen by structure is a lipoprotein, which participates in the transport functions of the membrane. The increased titer of total antimitochondrial antibodies (1: 160 and above) is characteristic of primary biliary cirrhosis (more than 90% of patients). A very small proportion of patients with primary biliary cirrhosis is AMA-negative. In secondary biliary cirrhosis, antimitochondrial antibodies are detected in low titers, or they are absent. Low titers of antimitochondrial antibodies can also be observed in chronic active hepatitis, chronic autoimmune hepatitis (up to 20% of cases), alcoholic or viral hepatitis.
Currently, 4 subtypes of antimitochondrial antibodies are isolated. Antibodies to M-2 mitochondrial antigens (a complex of enzymes on the inner membrane of mitochondria) are considered specific for primary biliary cirrhosis. The presence of antibodies against M-2 antigens can be detected by ELISA test systems. The diagnostic sensitivity of the test systems for the detection of primary biliary cirrhosis is 98%, specificity is 96%. Elevated is the content of antimitochondrial antibodies M-2 more than 25 IU / ml.
Along with anti-M2 antibodies in primary biliary cirrhosis, anti-M9, anti-M9 and anti-M8 antibodies are detected in most cases simultaneously, which react with different epitopes of the mitochondrial membrane. There is a relationship between the profile of antimitochondrial antibodies and the prognosis of primary biliary cirrhosis. Isolated detection in the serum of anti-M9 and / or anti-M2 correlates with a good prognosis of primary biliary cirrhosis. Progressing course of the disease is noted in patients with anti-M2, anti-M4 and / or anti-M8, in combination with increased serum bilirubin concentration.
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