M-cells in the rabbit tonsil exhibit distinctive glycoconjugates in their apical membranes.

Abstract

The tonsil crypt epithelium contains membranous (M)-cells that transport antigens from the lumen to underlying lymphoid cells, thereby initiating specific immune responses. Mechanisms mediating the adhesion of antigens to the M-cell surface are important for effective and selective uptake of potential pathogens but are still poorly understood. Therefore, the carbohydrates present on crypt epithelial cells of the rabbit palatine tonsil were studied by lectin histochemistry. Ultrathin LR White sections were incubated with a panel of eight lectins conjugated to colloidal gold or biotin. The glycocalyx of the apical membrane of M-cells was selectively labeled by UEA-I, LTA, HPA, and VVA, whereas that of the remaining squamous epithelial cells preferentially bound RCA-I and PNA. WGA and ConA showed only little binding, with no discernible preference for any of the cell types. Double labeling of UEA-1 together with anti-vimentin antibodies revealed that UEA-I-positive epithelial cells also contained the rabbit M-cell marker vimentin, and vice versa. The results show that a specific composition of glycoconjugates, which differs from that on squamous epithelial cells, is found on M-cells of the rabbit tonsil. The M-cell-specific glycoproteins and glycolipids could be selectively targeted by microorganisms that adhere to M-cells and enter the host along this pathway.

Examination of the Reticular Epithelium of the Bovine Pharyngeal Tonsil

“…Morphologically, Mcells described in the present study are similar, but not identical, to those described in sheep (Chen et al, 1991;Casteleyn et al, 2010). Tonsilar M-cells in rabbits have been identified through lectin or vimentin immunohistochemistry (Gebert, 1995(Gebert, , 1996(Gebert, , 1997. Recently, cytokeratin 18 was shown to be a marker of ileal dome M-cells in cattle .…”

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

“…Although some of the confocal images gave the impression that three subtypes of M-cells could exist according to the expression of ␣ 1-2-linked fucose or GalNAc, at the electron microscopic level no distinct subtypes were found, but rather a continuous spectrum of labeling intensities. Heterogeneity among the M-cells of individual domes has likewise been reported for the binding of the lectins UEA-I, AAA, and EEA to M-cells of murine Peyer's and cecal patches (Giannasca et al 1994;Clark et al 1995) and for the binding of UEA-I and Lotus lectin to M-cells in the palatine tonsil of rabbits (Gebert 1996). The lectin labeling of living tissue performed in the present study demonstrates that variations in the saccharide composition of the apical membrane of M-cells indeed exist in the living system, which probably play a role in the differential adherence to and uptake of antigens by M-cells.…”

The role of M cells in mucosal immunity

“…Peyer's patches Intestine wall 28% T cells yes (GALT) [15] CD4:CD8 ratio 3.7:1 70% B cells 2% macrophages NALT [15] Entrance of 40% T cells yes in rats [16] nasopharyngeal duct CD4:CD8 ratio 10:1 55% B cells 4.5% macrophages controversial BALT [17] At junctions between T cells in rabbits [18,19] CD4\CD8 bronchi and bronchioli or between the bronchus B cells macrophages and an artery [32] on some FAE enterocytes and in goblet cell mucins) Binding to UEA-1, Lotus tetragonolobus rabbit tonsil [34] (LTA), Helix pomatia (HPA), Vicia 6illosa (VVA) Vimentin rabbit gut and tonsils [35] not in mouse [23] tosis of macromolecules [27]. A further difference between M cells and absorptive enterocytes is the lectins which they can bind to their apical surfaces; for example the h-L-fucose-specific lectin Ulex europaeus agglutinin 1 (UEA-1) binds specifically to mouse PP M cells [28].…”