We have examined the distribution of the E2 component of pyruvate dehydrogenase complex in the liver of patients with native primary biliary cirrhosis (PBC), and after transplantation, using affinity-purified anti-E2 antibodies. In the posttransplantation group, we studied biopsy specimens from patients grafted for conditions other than PBC (n = 6) and those grafted for PBC with (n = 6) and without (n = 5 ) histological features suggestive of PBC recurrence. Features suggestive of PBC recurrence included portal tract granulomas, bile duct damage, ductopenia, and lymphoid aggregates. In the native liver from patients with PBC, there was increased staining of E2 on the biliary epithelial cells compared with hepatocytes, as previously described. However, in liver biopsy specimens from patients after transplantation, the pattern of staining of E2 was similar to that of normal, control liver in all three groups studied. These findings suggest that E2 overexpression on bile duct cells may not be important in the perpetuation of the bile duct damage in PBC, that expression in the allograft may be modified by immunosuppression, or that PBC does not recur in the allograft. (HEPATOLOGY 1995;22:798-801.) Primary biliary cirrhosis (PBC) is characterized by the presence in serum of antimitochondrial antibodies (AMA). These antibodies are virtually diagnostic of the disease'; the liver histology of patients with normal liver function tests but who have serum AMA often show features characteristic of PBC.' The major antigen recognized by M A has been identified as the E2 component of pyruvate dehydrogenase complex.:',4 We and others have shown that some biliary epithelial cells in patients with PBC have more E2 than would be expected considering the concentration of mitochondria; furthermore, E2 is present on the membrane of biliary epithelial cells isolated from livers of patients with PBC but not from livers of those with normal liver or with other liver disease^."^ It remains unclear Abbreviations: PRC. primary biliary cirrhosis; AMA, antimitochondrial a n -From the ' Liver Unit and the Department ol'Patholo~y, Queen Elizabeth