Uptake and transport of intestinal macromolecules and microorganisms by M cells in Peyer's patches--a personal and historical perspective.

Dr Kenzaburo Kumagai identified dome epithelium of intestinal lymphoid tissues as a site of uptake for mycobacteria in 1922, but he saw this only as a possible initiation point for intestinal tuberculosis and abandoned even that premise as non-specific, after finding that sheep red blood cells were also taken up. When development of ultrastructural techniques in 1972 permitted identification of M cells with phagocytic capabilities, harboring migrating lymphoid cells in the specialized epithelium over Peyer's patches, these patches remained anatomic curiosities with no recognized physiologic role. These structural observations of M cells and of intestinal lymphoid tissues stimulated functional, structural and molecular biologic investigations which now provide the basis for many of our current concepts of mucosal immunology and the roles of M cells in initiation of defensive immune responses. Copyright 1999 Academic Press.