The pepsin trypsin digest of the wheat prolamin gliadin (PT-gliadin) is deleterious to the small intestinal mucosa of coeliac patients. The handling of PT-gliadin by the intestinal epithelium in coeliac patients in remission and control individuals was investigated by in vivo instillation of PT-gliadin. The uptake of PT-gliadin was monitored by immunofluorescence microscopy of intestinal biopsy specimens, using affinity purified PT-gliadin antibodies. Control individuals show weak staining in the apical region of the enterocytes thereby showing an uptake of PT-gliadin. Coeliac patients have a conspicuous fluorescence in relation to the lateral membrane/intercellular space of enterocytes and intense staining intracellularly in the apical region. There is only weak staining in the enterocytes after the instillation was terminated, indicating an intracellular clearance. The study shows that normal enterocytes are able to take up PT-gliadin. The increased uptake in coeliac patients might be of importance for the pathogenesis either by direct toxicity or by presentation to immunocompetent cells. Furthermore, the results are in agreement with the suggestion of a functional alteration in the zonula occludens in the intestinal epithelium of coeliac patients
