Immunomodulatory Effects of Orally Administered Bifidobacterium Components on Intestinal Lymphoid Tissues

摘要

To clarify the immunomodulatory effects of orally administered Bifidobacterium pseudocatenulatum 7041 (Bp) as probiotic bacteria, we determined the IgA production and cytokine secretion by lymphocytes derived from each of the intestinal immune tissues(e.g. Peyer's patch, PP; cecal follicle, CF; and mesenteric lymph node, MLN). It was demonstrated that IgA production and cytokine secretion (e.g. IL-5, IFN-gamma) by lymphocytes derived from each intestinal immune tissue were significantly increased following the oral administration of Bp to BALB/c mice for 7 consecutive days. In order to clarify the nature of the immunomodulatory mechanisms induced by the oral administration of Bp, we investigated immunohistochemi-cally bacterial migration and localization in vivo after a single-shot oral injection of Bp using Bp fluorescently-labeled with CFSE. CFSE-labeled Bp spots in tissue sections were observed in the PPs 1 h after the single-shot oral administration. These results indicated that orally administered Bp were taken up by the PPs through M cells and suggest that oral injection of Bp induces immunomodulation directly following uptake of bacterial components into the intestinal lymphoid tissues. Additionally, the immunomodulation by Bp acted through the activation of CD4~+ cells in the PP.