Immunoreactivity to pyruvate dehydrogenase complex-E2 in well-defined patients with autoimmune hepatitis: Western blot analysis.

Anti-mitochondrial antibodies (AMA) are frequently detected in sera from patients with primary biliary cirrhosis (PBC). Major autoantigens for AMA have been identified as members of the 2-oxoacid dehydrogenase enzyme complex family, with pyruvate dehydrogenase complex (PDC)-E2 showing strongest reactivity to AMA in PBC patients. Recently, anti-PDC-E2 has been found in patients with other diseases. Since frequency and significance of anti-PDC-E2 in patients with autoimmune hepatitis (AIH) remain obscure, we measured anti-PDC-E2 in sera from well-defined AIH cases by Western blotting using bovine heart mitochondrial protein and recombinant PDC-E2 protein as antigen sources. All 55 enrolled patients fulfilled the international diagnostic criteria for definite or probable AIH. Anti-PDC-E2 positivity showed concordance between native and recombinant antigens. Anti-PDC-E2 was detected in nine of 55 sera from AIH patients (16%). Variables including alkaline phosphatase (ALP) and IgM concentrations, effects of prednisolone, and pathologic findings concerning bile ducts showed no significant differences between anti-PDC-E2-positive and anti-PDC-E2-negative AIH patients. These data indicate that detection of anti-PDC-E2 is not rare in defined AIH, but anti-PDC-E2-positive AIH does not represent an intermediate entity in a clinical spectrum between AIH and PBC.