Background/Aims: Intestinal epithelial cells present protein antigens to primed T cells in vitro. The aim of this study was to investigate whether intestinal epithelial cells present peptide antigens in vitro and in vivo after oral administration. Methods: Small intestinal epithelial cells from naive LEW (RT1¹) rats pulsed in vitro with a synthetic immunogenic major histocompatibility complex allopeptide, RT1.D^uβ20–44, or in vivo by oral administration of the peptide were tested for their ability to induce specific proliferation of LEW T cells primed in vivo to RT1.D^uβ20–44. Results: In vitro pulsed intestinal epithelial cells induced specific proliferation of RT1.D^uβ20–44-primed T cells. Intestinal epithelial cells isolated from LEW rats that received a single oral dose of RT1.D^uβ20–44 18 hours earlier also induced specific proliferation of RT1.D^uβ20–44-primed LEW T cells. Furthermore, epithelial cells harvested from LEW rats that received WF (RT1^u) splenocytes orally 18 hours earlier induced specific proliferation of RT1.D^uβ20–44-primed LEW T cells. Conclusions: Intestinal epithelial cells take up processed alloantigen in vitro and in vivo for presentation as peptides to primed T cells. These observations provide a novel approach to study the role of the intestinal immune system in immune regulation in vivo.