Characterization of autoantibodies against components of the nuclear pore complexes: high frequency of anti-p62 nucleoporin antibodies.

Antibodies against nuclear components (ANAs) occur in sera of approximately 50% of patients with primary biliary cirrhosis (PBC). By indirect immunofluorescence (IIF) ANA-positive PBC sera generate most frequently, homogeneous, speckled, centromere, and rim-like staining patterns. A perinuclear staining pattern is indicative for the reactivity of the sera with the components of the nuclear envelope. A substantial subset of PBC patients develops antibodies against constituents of the nuclear pore complexes (NPCs). These autoantibodies target two major autoantigens: gp210 glycoprotein and p62 kDa nucleoporin. Originally, a strong reaction of PBC with a 60 kDa protein of NPCs that was affinity purified on wheat-germ agglutinin (WGA)-Sepharose was described. Recently, using human recombinant p62 nucleoporin the identity of the reactivity was confirmed. In this work we compared by immunoprecipitation the reactivity of 20 PBC sera with the two recombinant autoantigens of the NPCs. Two out of 20 (10%) PBC sera precipitated recombinant gp210 glycoprotein and 11 out of 20 (55%) PBC sera reacted with p62 nucleoporin. These results evidence that anti-p62 antibodies occur more frequently than the autoantibodies against gp210 glycoprotein. Considering the recently reported clinical significance of ANAs in PBC, the prognostic value of the anti-NPC antibodies and their correlation with severity and progression of the disease is under evaluation.