AIMS: This study aimed to elucidate in vitro how orally administered Streptococcus thermophilus 1131 and Lactobacillus delbrueckii subsp. bulgaricus 2038, stimulated immune cells in the gut lamina propria and thereby enhanced the intestinal barrier function, as reported in our previous study. METHODS AND RESULTS: We prepared an M cell model by coculturing small intestinal epithelial cells derived from human induced pluripotent stem cells with Raji cells. In this model, we demonstrated that both strains were incorporated into M cells and translocated to the basolateral side via transcytosis. Evaluation of the immune response using peripheral blood mononuclear cells showed that S. thermophilus 1131, translocated via M cells, induced the secretion of several cytokines, including IL-22 and IL-23. CONCLUSION: We showed that both strains were transcytosed by M cells in a human gut model. The results suggested that oral administration of both strains induced immune responses by translocating from the gut lumen to the lamina propria via M cells.
Yamazaki et al. (Thu,) studied this question.