Gliadin presented via the gut induces oral tolerance in mice

When an antigen is first presented via the gut, either priming or suppression of the systemic immune response may result. Many factors influence the outcome, including physico-chemical properties of the antigen. The aim of this study is to establish if wheat gliadin behaves as an oral immunogen or tolerogen. Mice reared on a gluten-free diet were fed gliadin, either as wheat flour in a standard rodent diet or as the purified molecule. Immune status (tolerant or sensitized) was then defined by measuring specific systemic immune responses after parenteral immunization of gliadin-fed and control mice. A single feed of 25 or 125 mg of purified gliadin resulted in a dose-dependent suppression of both cell-mediated and humoral immune responses. Similar oral tolerance was achieved by feeding mice with a gluten-containing diet for a week. Finally, mice reared on a normal, gluten-containing diet showed evidence of established oral tolerance, with significantly lower systemic immune response to gliadin than mice reared on gluten-free diet. These results indicate that gliadin is an effective oral tolerogen. In vivo studies on the immunogenicity of gliadins should be conducted in animals from gluten-free colonies.