RESUMEN
Colonization of V. cholerae O1 in vivo is known to be a non-invasive type which the vibrios are confined only to the intestinal tissues. The pathway by which the vibrio antigens reach the lymphoid cells and subsequently give rise to the immune responses is not entirely clear. Thus, experiments were performed in experimental rats by inoculating live V. cholerae O1 into the ligated ileal loops. The fate of the vibrios in the intestinal tissues was then studied by transmission electron microscopy at different times after the inoculation. It was concluded that live V. cholerae O1 were initially taken up by the M cells which overlay Peyer's patches and which subsequently delivered the intact vibrios to phagocytic cells in the Peyer's patches. These phagocytic cells processed (digested) the vibrios while the lymphocytes and plasma cells infiltrated around them. During the late period of infection (12-15 hours after inoculation of the vibrios), vibrios were also found passing through the loose intercellular spaces between the absorptive epithelial cells into the underlying intestinal tissues.