Isotypic distribution of anti-pyruvate dehydrogenase antibodies in patients with primary biliary cirrhosis and their family members.

IgG subclasses of anti-pyruvate dehydrogenase (PDH) antibodies were determined in 72 patients with primary biliary cirrhosis. All isotypes were detected, but IgG3, IgG1, and IgG2 predominated independently or in association. An average of 33.3 +/- 19.1% of the anti-PDH IgG was IgG1 (mean optical density, 0.863 +/- 0.783, vs 0.053 +/- 0.038 in the normal controls), 25.0 +/- 17.8 IgG2 (0.652 +/- 0.656 vs 0.062 +/- 0.030), 39.5 +/- 23.4% IgG3 (1.140 +/- 0.917 vs 0.010 +/- 0.023), and 2.4 +/- 7.4% IgG4 (0.060 +/- 0.182 vs 0.012 +/- 0.007). Anti-PDH IgG were restricted to IgG1 in the family members of patients (0.180 +/- 0.403).