PREFERENTIAL INTERACTION OF SALMONELLA-TYPHIMURIUM WITH MOUSE PEYERS PATCH M-CELLS

We have used a mouse Peyer's patch gut loop model to investigate the r ole of the intestinal membranous epithelial (M) cells in the pathogene sis of Salmonella typhimurium. These specialized antigen sampling cell s are located in the follicle-associated epithelium (FAE) overlying th e isolated and aggregated lymphoid follicles in the small and large in testines. Our studies have demonstrated that S. typhimurium adheres mo re frequently to the Peyer's patch FAE cells than to the villous enter ocytes and that, within the FAE, this bacterium preferentially interac ts with the M cells. Quantitative light microscopic: studies, using th e lectin Ulex europaeus 1 (UEA1) to identify M cells, revealed that 34 -fold more bacteria bound per unit area of M cells than per unit area of enterocyte. Within a 30-min incubation period, some M cells had cle arly been invaded by the Salmonella. We therefore propose that M cells are a major route by which S.typhimurium penetrates the intestinal ep ithelial barrier. Bacterial adhesion to M cells occurred in a non-unif orm pattern, suggesting the existence of M-cell subtypes. The interact ion of S. typhimurium with mouse Peyer's patch M cells was accompanied by membrane ruffle formation and polymerized actin redistribution sim ilar to that observed in cultured cell lines infected by this bacteriu m. This study emphasizes the suitability of Salmonella as an oral vacc ine delivery system since, by preferentially interacting with the M ce lls, these bacteria are targeted to sites where cells of the immune sy stem are concentrated.