Effects of antigen challenge on intestinal permeability and morphology in rats immunized with gliadin or ovalbumin

In this study we have investigated the possible effects of a local immune response on the intestinal permeability and morphology in rats. The animals were immunized subcutaneously by small doses of gliadin or ovalbumin. Immunization with gliadin led to small but significantly increased levels of IgA and IgM antibodies, similar to those reported for patients with coeliac disease. Immunization with ovalbumin gave significantly increased antibody levels of IgE, IgG, IgA and IgM. Subsequent antigen provocations by oral administration of gliadin (1 mg), together with fluorescein isothiocyanate-labelled dextran (molecular weight 3,000 daltons) as permeability marker, resulted in an increased intestinal permeability for this marker. This alteration of the intestinal permeability was qualitatively similar to that previously reported for patients with coeliac disease. Antigen provocation with ovalbumin caused a decreased permeability for both dextran and different-sized polyethylene glycols, but first at a dose of 40 mg. Direct antigen administration (gliadin or ovalbumin) into a ligated part of the ileum gave qualitatively similar but less pronounced permeability changes when compared with the effects obtained after oral administration of the respective antigen. However, neither gliadin nor ovalbumin challenge led to any ultrastructural changes of the intestinal wall. In summary, we have been successful in inducing specific antibody responses towards gliadin in rats and increased intestinal permeability upon gliadin provocation without any coexisting morphological alterations.