antibody IgGsubclass distribution andaffinity inprimary biliary cirrhosis

SUMMARYWe have studied the total IgG subclass and anti-mitochondrial antibody (AMA) specific IgG subclassdistributioninprimarybiliarycirrhosis (PBC) sera. Inorder to solvetheproblemscausedbythe differingaffinitiesofsubclassspecificmonoclonalsandthe competitiveinhibitionofantibodiesin a whole serum assay, six sera were separated into subclass-specific fractions by affinity-depletion chromatography.AMAsubclassdistributionof 20 further sera from patientswithPBC was assessed usingconventionalmethodsandtheresults were calibratedagainst one of the fractionated sera. Lightchain distribution andAMAfunctional affinity were also assessed for the fractionated subclasses. Total amounts of IgG3 were significantly increased compared with normal controls. AMA were foundin all IgGsubclasses and not restricted predominantly to IgG3 as previously described. The functional affinity of IgG3 AMAis generally lower as comparedwith that ofother subclasses. No light chain restriction was found.Keywords Primary biliary cirrhosis IgG subclasses anti-mitochondrial antibodies