Patients with primary biliary cirrhosis frequently develop autoantibodies 
directed to gp210, a major glycoprotein of the nuclear pore complex. This 
protein contains a large glycosylated cisternal domain, a single transmembrane 
segment, and a short cytoplasmic tail. It has been previously shown that 
autoantibodies from primary biliary cirrhosis patients exclusively react with 
the cytoplasmic tail. We demonstrate that autoantibodies against gp210 recognize 
at least two different epitopes. 4 out of 12 anti-gp210 positive sera reacted 
with the fragment consisting of the cytoplasmic tail, and 8 sera targeted a 
novel epitope located within the large glycosylated lumenal domain. Moreover, 
our data prove that carbohydrate moieties are an essential part of this novel 
epitope. We propose, therefore, that future screening assays should be performed 
with antigens possessing both epitopes to detect all sera with anti-gp210 
specificity.