M Cell Transport of Vibrio cholerae from the Intestinal. Lumen into Peyer's Patches: A Mechanism for Antigen Sampling and for Microbial Transepithelial Migration

Abstract

Viable Vibrio cholerae O1 were inoculated into the intestinal lumen of nonimmune rabbits. The vibrios were phagocytosed by Mcells over Peyer's patch lymphoid follicles, carried in vesicles through the epithelium, and discharged among underlying lymphocytes and macrophages. Autoradiography of V. cholerae labeled with [2-³H]adenine confirmed transport. Indigenous bacteria with and without capsules were also taken up from controlloops and carried through M cells into Peyer's patches. V. cholerae killed by acidification, formalin, heat, or UV irradiation were not taken up, a result that may have relevance for development of oral vaccines. Ruthenium red stain revealed gaps in the layer of mucus over M cells, glycocalyx bridging the space between vibrios and M cell microvilli, and knobby projections over membranes of M cell microvilli; these projections were not found over absorptive cells. M cells thus convey viable enteric microbes, including V. cholerae that are not otherwise invasive, into intestinal lymphoid tissue, where mucosal immune responses are initiated. Uptake and transport by M cells may also assist certain pathogenic bacteria in traversing the mucosal barrier and initiating systemic infection.