Comparative immunoreactive profiles of Japanese and American patients with primary biliary cirrhosis against mitochondrial autoantigens.

Primary biliary cirrhosis (PBC) has been described among various ethnic and racial populations in all parts of the world. However, the incidence and prevalence of PBC varies considerably in different geographic areas. It has the highest frequency in Northern Europe, is considerably lower in Japan and still lower in other parts of Asia. There has not hitherto been a detailed immunological profile of antimitochondrial antibodies according to geographic region. We have used recombinant or purified preparations from the 2-oxo-acid dehydrogenase enzyme complexes, the major mitochondrial autoantigens in PBC (PDC-E2, BCOADC-E2, OGDC, protein X and PDC-E1 alpha) to compare the reactivity of sera from either similarly staged sera from Japanese (n = 23) or American-Caucasian patients (n = 39) with PBC. In all cases, the first available sera following diagnosis was selected. Interestingly, only 65% of Japanese patients reacted by ELISA with PDC-E2 compared with more than 95% of the North American group. Moreover, the level of enzyme-inhibitory antibodies to PDC was lower in the Japanese. Our findings prompt the need for characterization of specific susceptibility genes and environmental factors in various parts of the world to clarify the etiology of PBC.