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In the intestine, lymphoid nodules, individually or aggregated into Peyer’s patches, are sites where antigen recognition begins and mucosal immune responses are initiated. M cells in the epithelium covering these lymphoid nodules are specially differentiated to take up and transport antigenic macromolecules and microorganisms from the lumen across the epithelial barrier, that otherwise restricts potential systemic pathogens to the lumen and prevents unregulated migration into tissues. M cells, enterocytes, goblet cells, and other epithelial cells lining the intestine and other mucosal surfaces are end stage cells, replaced from stem cells in an unending flow, that allows cells, physiologically infected by luminal microorganisms after emerging from the mouths of crypts, to be continually replaced by fresh recruits. Since M cells were first identified in humans in 1974,1 a major limitation and challenge for investigators has been their inability to grow M cells in culture under controlled conditions where regulation of growth, development, and function could be delineated.

Lack of methods for in vitro investigation of lymphoid follicle epithelium, except in short term organ culture, …