Glycoconjugate expression defines the origin and differentiation pathway of intestinal M-cells.
Intestinal M-cells are specialized epithelial cells located in the domes of the gut-associated lymphoid tissues, which transport antigens from the lumen to the underlying lymphoid tissue, thereby initiating immune reactions. It is assumed that M-cells arise from stem cells in the crypts, from which they migrate to the top of the domes. To study the differentiation pathway of M-cells, we used the rabbit cecal lymphoid patch in which the M-cells express high levels of alpha 1-2-linked fucose and N-acetyl-galactosamine residues in their apical membrane. Dome areas were labeled with fluorescein- and rhodamine-conjugated lectins specific for alpha 1-2-linked fucose and N-acetyl-galactosamine in vivo and in vitro, and were observed with confocal laser scanning microscopy. Ultrathin sections were double labeled with lectin-gold conjugates and the labeling density was quantified by computer-based image analysis. All cecal patch M-cells expressed alpha 1-2-linked fucose and N-acetyl-galactosamine, but the amount of the two saccharides varied considerably depending on the position of the M-cells at the base, flank, or top of the dome. In eight of 18 rabbits studied, radial strips of M-cells with common glycosylation patterns were observed, each strip associated with an individual crypt. Confocal microscopy revealed that lectin-labeled M-cells were not restricted to the dome epithelium but were also detected in the upper third of crypts surrounding the domes. The results show that M-cells are heterogeneous concerning the glycosylation pattern of membrane glycoconjugates. This pattern is modified as the M-cells differentiate and migrate from the base to the top of the dome. Radial strips of M-cells with a common proclivity of glycoconjugate expression suggest that those M-cells that derive from the same crypt have a clonal origin. The presence of (pre-) M-cells in the crypts surrounding the domes indicates that M-cells derive directly from undifferentiated crypt cells and do not develop from differentiated enterocytes.
Gebert
A
A
Center of Anatomy, Medical School of Hannover, Germany.
Posselt
W
W
D000818:Animals; D002432:Cecum / Q000166:cytology / Q000378:metabolism*; D002465:Cell Movement; D004848:Epithelium / Q000378:metabolism; D005456:Fluorescent Dyes; D006001:Glycoconjugates / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D037102:Lectins / Q000378:metabolism; D008221:Lymphoid Tissue / Q000166:cytology / Q000378:metabolism*; D008297:Male; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D037121:Plant Lectins; D011817:Rabbits
D005456:Fluorescent Dyes; D006001:Glycoconjugates; D037102:Lectins; D037121:Plant Lectins; C036850:Ulex europaeus lectins; C042242:Vicia lectins