Mid-life crisis for M cells

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Abstract
Lack of methods for in vitro investigation of lymphoid follicle epithelium, except in short term organ culture, has required deductive approaches to understanding factors which regulate M cell differentiation. Bye et al found that M cells already display detectable differences in enzymatic, cytoskeletal, and surface characteristics upon emerging from crypt mouths.2Remarkably, cells streaming from mouths of crypts surrounding intestinal lymphoid nodules show enterocyte characteristics when they flow from the sides of crypt walls next to villi, but on the opposite side of the same crypts, M cells originate from stem cells abutting lymphoid follicles. This observation generated the hypothesis that lymphocytes or their intercellular mediators provide stimuli directing differentiation of intestinal epithelial stem cells.