Characterization of antigens from the human exocrine pancreatic tissue (Pag) relevant as target antigens for autoantibodies in Crohn's disease.

ABSTRACT

BACKGROUND: The present study was performed to analyse the immunological properties of the autoantigens recognized by autoantibodies against exocrine pancreas (PAb), which have been described in Crohn's disease. METHODS: Autoantibodies were detected by indirect immunofluorescence. Inhibition studies were performed by preincubating tissue sections with various glycoproteins and the different fractions obtained in fractioned salt precipitation of pancreas homogenate with ammonium sulphate. Immunoblotting of human pancreas homogenate was conducted using PAb-positive sera. RESULTS: In size exclusion chromatography, the molecular weight of the pancreas autoantigen (PAg) was determined as > 800 kD. In the fractionated salt precipitation, the autoantigen could be detected in fractions I (0-25% ammonium sulphate) and III (50-90% ammonium sulphate). In immunoblotting, a number of protein bands were observed (at 16, 18, 19, 24, 27, 29, 31 and 34 kD), and the binding pattern showed little variation between individual patients. CONCLUSIONS: The protein that is recognized by PAb appears to be a large protein complex consisting of several subunits which exhibit reactivity to PAb.