Epithelial M cells in the rabbit caecal lymphoid patch display distinctive surface characteristics

Abstract

The follicle-associated epithelium (FAE) in the rabbit caecal lymphoid patch is characterized by the presence of membranous (M) cells, which are believed to be functionally equivalent to those present at other sites of gut-associated lymphoid tissue (GALT). Caecal patch M cells display distinctive features compared with those of other GALT sites, despite similar general morphology and expression of the M cell marker vimentin, suggesting marked heterogeneity in the apical surface of M cells at discrete GALT sites. Electron microscopy reveals that rabbit caecal patch M cells differ from those in the small intestinal Peyer's patch FAE: the former have a prominent aspect within the epithelium and possess microvilli which are longer than those of adjacent enterocytes. Many of the M cells in peripheral regions of the caecal patch FAE are not associated with leucocytes and may thus represent an immature M cell population. The M cells are also histochemically distinct from adjacent enterocytes and from Peyer's patch M cells, showing greater expression of brush-border alkaline phosphatase activity and affinity for certain lectins (peanut and wheat germ agglutinins, Bandeiraea simplicifolia agglutinin II). The differences in the brush-border morphology and glycocalyx structure between M cells at different GALT sites may affect their function at these sites by influencing the interaction of luminal antigens and microorganisms with the M cell surface. The present data also support the hypothesis that M cells arise directly from differentiation of crypt stem cells and not from the transformation of existing fully differentiated enterocytes.

Cellular Kinetics of Villous Epithelial Cells and M Cells in Rabbit Small Intestine

“…The second theory is that M cells are derived directly from undifferentiated cells in the intestinal crypt. In the rabbit ileal Peyer's patch and appendix, a majority of M cells at the periphery of the lymphoid follicle are located adjacent to the intestinal crypt [9,10]. The finding supports the second hypothesis.…”

“…The first hypothesis is that M cells transform from mature microvillous epithelial cells of the FAE [3,[17][18][19]. The second is that M cells differentiate directly from undifferentiated cells in the crypt [4,[8][9][10]. In the rabbit intestine, the cellular kinetics of villous columnar epithelial cells has not yet been clarified, although the morphology and distribution of M cells have been reported in detail [8,10].…”

Glycoconjugate Expression Defines the Origin and Differentiation Pathway of Intestinal M-cells

“…Previous lectin histochemical studies on the rabbit gutassociated lymphoid tissue demonstrated that M-cells of the rabbit cecal lymphoid patch express high levels of ␣ 1-2-linked fucose and GalNAc residues in their apical membrane (Gebert and Hach 1993;Jepson et al 1993a). Although the biological significance of these membrane-bound glycoconjugates is not completely understood (Clark et al 1993;Gebert and Hach 1993;Jepson et al 1993a;Giannasca et al 1994), the rabbit cecal patch represents an appropriate model for studying the origin, differentiation, and migration of M-cells.…”

“…Although the biological significance of these membrane-bound glycoconjugates is not completely understood (Clark et al 1993;Gebert and Hach 1993;Jepson et al 1993a;Giannasca et al 1994), the rabbit cecal patch represents an appropriate model for studying the origin, differentiation, and migration of M-cells.…”

“…Previous studies (Gebert and Hach 1993;Jepson et al 1993a) revealed that M-cells of the rabbit cecum express large amounts of ␣ 1-2-linked fucose and N -acetyl-galactosamine (GalNAc) on their apical membrane, a specialization that can be employed as a sensitive marker for M-cells at this location and in their differentiation pathway. In the present study, the cecal lymphoid patch of the rabbit was used as a model to study changes in the glycosylation patterns of the dome epithelial cells during their lifespan and their migration from the dome-associated crypts to the top of the domes.…”