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Primary biliary cholangitis (PBC) is a chronic non-suppurative cholangitis with progressive inflammatory destruction of the small bile ducts.
Autoantibodies can be detected several years before the onset of PBC. More than 90% of PBC patients are positive for anti-mitochondrial antibodies (AMA), particularly for those directed against the antigens M2, M4, M8 and M9.
Around 80-90% of PBC patients show reactivity on AMA M2 (PDH)
The mitochondrial M2 antigen mainly comprises the domains of the E2 subunits of the following:
- Pyruvate dehydrogenase complex (PDH)
- 2-oxoglutarate dehydrogenase complex (OGDH)
- Branched-chain 2-oxoacid dehydrogenase complex (BCOADH)
M4 and M9 represent additional autoimmune targets in PBC.
Antibodies against M4 is found in up to 55% of PBC patients.
IgM autoantibodies against M9 mostly occur in the early phase of PBC and have been reported to be a severity marker for the disease.
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