Humoral and cellular immune responses to dihydrolipoamide dehydrogenase (E3): lack of specificity for primary biliary cirrhosis.

Immune responses to dihydrolipoamide dehydrogenase, the E3 subunit which is a common component of 2-oxoacid dehydrogenase complexes, have been suggested to be associated with the etiology of primary biliary cirrhosis (PBC). However, since an antibody to E3 could be detected in Caucasian patients with PBC, but was not specific for the disease, the proposal is not evident at the antibody level. We have identified the antibody also in Japanese patients with PBC by immunoblotting with sera at a 1:100 dilution and have assessed cellular immune responses to E3 by proliferation assay of peripheral blood lymphocytes. Anti-E3 antibody was detected more frequently in 25 of 43 PBC (58.1%) than in normal controls (p < 0.01) and in chronic liver diseases (p < 0.05), but the antibody was not specific for PBC as reported in Caucasian PBC. Anti-E3 antibody-positive sera of PBC patients or normal controls and their IgG fraction did not inhibit the enzyme activity of E3. Lymphocyte blastogenesis to E3 in PBC was significantly greater than normal controls (p < 0.05), but was not significant as compared with chronic liver disease or non-hepatic autoimmune diseases. Thus, these data do not support the hypothesis that the immune response to the E3 subunit is associated with etiology of PBC.