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

Background The present study was performed to analyse the immunological pro perties of the autoantigens recognized by autoantibodies against exocrine p ancreas (PAb), which have been described in Crohn's disease. Methods Autoantibodies were detected by indirect immunofluorescence. Inhibi tion studies were performed by preincubating tissue sections with various g lycoproteins and the different fractions obtained in fractioned salt precip itation of pancreas homogenate with ammonium sulphate. Immunoblotting of hu man pancreas homogenate was conducted using PAb-positive sera. Results In size exclusion chromatography, the molecular weight of the pancr eas autoantigen (PAg) was determined as > 800 kD. In the fractionated salt precipitation, the autoantigen could be detected in fractions I (0-25% ammo nium sulphate) and III (50-90% ammonium sulphate). In immunoblotting, a num ber 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 patie nts. Conclusions The protein that is recognized by PAb appears to be a large pro tein complex consisting of several subunits which exhibit reactivity to PAb .