Tolerance to ingested deamidated gliadin in mice is maintained by splenic, type 1 regulatory T cells
Background & Aims: Patients with celiac disease have permanent intolerance to gluten. Because of the high frequency of this disorder (approximately 1 in 100 individuals), we investigated whether oral tolerance to gluten differs from that to other food proteins. Methods: Using transgenic mice that express human HLA-DQ2 and a gliadin-specific, humanized T-cell receptor, we compared gluten-specific T-cell responses with tolerogenic mucosal T-cell responses to the model food protein ovalbumin. Results: Consistent with previous findings, the ovalbumin-specific response occurred in the mesenteric lymph nodes and induced Foxp3+regulatory T cells. In contrast, ingestion of deamidated gliadin induced T-cell proliferation predominantly in the spleen but little in mesenteric lymph nodes. The gliadin-reactive T cells had an effector-like phenotype and secreted large amounts of interferon gamma but also secreted interleukin-10. Despite their effector-like phenotype, gliadin-reactive T cells had regulatory functions, because transfer of the cells suppressed a gliadin-induced, delayed-type hypersensitivity response. Conclusions: Ingestion of deamidated gliadin induces differentiation of tolerogenic, type 1 regulatory T cells in spleens of HLA-DQ2 transgenic mice. These data indicate that under homeostatic conditions, the T-cell response to deamidated gliadin is tolerance, which is not conditioned by the mucosal immune system but instead requires interleukin-10 induction by antigen presentation in the spleen.