Defective 'gut processing' of gliadin in mice with graft-versus-host enteropathy.

The gut mucosa plays an important role in the induction of oral tolerance. Extending previous observations, we have here shown that serum containing gut-absorbed gliadin induces suppression of the specific systemic immune response in recipient mice parenterally immunized with gliadin. Graft-versus-host reaction (GvHR) has profound effects on the gut mucosa, representing a model of immune-mediated enteropathy. The aim of our work was to investigate the gut handling and processing of gliadin in mice with GvHR. Binding to enterocytes, passage through the epithelium, and ability of the epithelium to convert this antigen into a tolerogenic form were assessed in BDF1 mice weaned on gluten-free diet, 2 weeks after the induction of a semiallogeneic GvHR. Binding of gliadin peptide B3144 to enterocytes was similar in controls and GvHR mice. After feed, serum levels of gliadin were comparable in the two groups of mice, but when serum collected from GvHR mice and containing gut-absorbed gliadin was transferred intraperitoneally into naive recipient mice, this did not induce suppression of the specific immune response. These experiments indicate that during GvHR enteropathy the ability of the intestine to convert gliadin into a tolerogenic form is lost. Defective antigen gut processing may contribute to the observed failure in oral tolerance induction.