Serial changes of serum anti-M2 proteins in patients with primary biliary cirrhosis: A follow-up study by immunoblotting

To investigate the pathogenic role of M2 components in primary biliary cirrhosis (PBC), we studied the serial changes of serum anti-M2 protein profiles by immunoblotting in 21 patients with PBC who were observed for at least 3 years. Immunoblotting was done using bovine heart mitochondrial fraction as the antigen. First, we confirmed the antigen specificity by inhibition tests using recombinant proteins associated with two types of major M2 proteins. At the initial examination, 15 patients showed positivity for the 74-kDa protein corresponding to anti-PDC-E2, and 19 patients showed the 50-kDa protein corresponding to anti-BCOADC-E2. In subsequent examinations, four of the 21 patients continuously did not show the 74-kDa protein and only one patient showed the 50-kDa protein although it was not detected at the initial examination. The anti-M2s other than 74-kDa protein, especially 50-kDa protein, showed almost no changes from the initial examinations. These data indicate that part of the onset and development of PBC is highly associated with M2 proteins other than PDC-E2.