The pathophysiology of glandular dysfunction in Sjögren's syndrome (SS) has not been fully elucidated. Previously, we reported the presence of autoantibodies to AQP-5 in patients with SS, which was associated with a low resting salivary flow. The purpose of this study was to investigate the presence of anti-AQP1 autoantibodies. To detect anti-AQP1 autoantibodies, cell-based indirect immunofluorescence assay was developed using MDCK cells that overexpressed human AQP1. By screening 112 SS and 52 control sera, anti-AQP1 autoantibodies were detected in 27.7% of the SS but in none of the control sera. Interestingly, the sera that were positive for anti-AQP1 autoantibodies also contained anti-AQP5 autoantibodies in the previous study. Different from anti-AQP5 autoantibodies, the presence of anti-AQP1 autoantibodies was not associated with the salivary flow rate. Although anti-AQP1 autoantibodies are not useful as a diagnostic marker, the presence of autoantibodies to AQP1 may be an obstacle to AQP1 gene therapy for SS.
Keywords: Aquaporin 1; Autoantibodies; Fluorescent antibody technique; Sjögren's syndrome.