M2 antibodies | LKM 1 antibodies

M2 antibodies

Antigens

Mitochondrial autoantigens are subunits of the 2-oxo acid dehydrogenase complexes, and are located in the inner mitochondrial membrane of eukaryotic cells. The primary function of the 2-oxo acid dehydrogenase complex is channelling electrons via oxidative decarboxylase reactions. Today, nine different AMA subclasses are distinguished (M1 to M9), of which M2 is the most important as a marker for primary biliary cirrhosis (PBC). M2 antibodies recognize components of the enzyme pyruvate dehydrogenase (PDH). The antigens (approx. 74, 52, 45 and 39 kDa) are ubiquitous in mammalian and yeast mitochondria, as well as in bacteria and chloroplasts. Three of the four M2 antigens are E2 enzymes, which catalyse the transfer of the respective decarboxylated residue from the E1-enzyme (decarboxylase) to coenzyme A. The fourth M2 component is represented by protein X, which is found in association with PDH.

The Varelisa M2 Antibodies assay uses purified pyruvate dehydrogenase.

Antibody specificity and prevalence

Primary biliary cirrhosis, PBC (96%), differential diagnosis from autoimmune hepatitis.

Information about primary biliary cirrhosis

Disease activity

AMA concentrations do not correlate with disease stages and prognosis. The effects of drug therapy on AMA levels are limited.

When is the measurement recommended?

• Suspicion of primary biliary cirrhosis (PBC)

Antibody isotype

IgG

References

Leung PSC, Coppel RL, Gershwin E (1996)  |  Baum H (1995)  |  Berg PA, Klein R (1992) 

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LKM 1 antibodies

Antigens

Liver/kidney microsomal (LKM) antibodies are characterized using indirect immunofluorescence by their reaction with the cytoplasm of hepatocytes and proximal, but not distal, renal tubules. Anti-LKM 1 antibodies react with the 50 kDa cytochrome P 450 II D6, which is one of at least 15 human hepatic P450 isozymes involved in phase I drug metabolism.

The Varelisa LKM 1 Antibodies assay uses human recombinant cytochrome P450 II D6.

Antibody specificity and prevalence

• Autoimmune hepatitis type II (100%, because AIH type II is characterized by positive LKM 1) 
• Chronic hepatitis C (7%) 
• Halothane hepatitis (very rare)

Disease activity

LKM 1 antibody concentrations do not correlate with disease stages.

When is the measurement recommended?

Suspicion of autoimmune hepatitis

Antibody isotypes

IgG

References

Manns MP (1996)  |  Obermayer Straub P, Strassburg CP, Manns MP (2000)  |  Mann MP, Rambusch EG (1996) 

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