Antigen-specific regulatory T cells are detected in Peyer's patches after the interaction between T cells and dendritic cells loaded with orally administered antigen

Systemic immune tolerance is induced for orally administered antigen, and this phenomenon is called oral tolerance. However, the mechanism of oral tolerance has not been completely elucidated. It has been suggested that antigen presentation and generation of regulatory T cells in Peyer's patches (PPs) are important for induction of oral tolerance. Hence, we orally administered fluorescence-labelled antigen to mice and examined kinetics of the antigen and interaction between antigen-loaded dendritic cells and T cells. It was visualized that dendritic cells in PP rapidly take up antigen. We next transferred antigen-specific naïve T cells from T cell receptor transgenic mice and administered the antigen orally. Antigen-specific T cells accumulated in IFR in PP and DCs that have ingested antigen come in contact with antigen-specific T cells in IFR. The accumulated T cells were then collected and analyzed for the pattern of gene expression by real-time PCR, which revealed a gene expression pattern similar to that of FoxP3-positive regulatory T (T_reg) cells. CCR9, an intestinal homing marker, was also strongly expressed. These results suggest that DCs that have captured oral antigens in PPs locally induce antigen-specific naïve T cells to differentiate into T_reg cells with the intestinal homing phenotype.