Differential Binding of Lectins to M Cells and Enterocytes in the Rabbit Cecum

Background: The afferent limb of the intestinal immune system is represented by the gut-associated lymphoid tissue, in which antigenic material, including complete bacteria, is taken up from the lumen by specialized epithelial cells (M cells). Because the adherence of micro-organisms to epithelial can be mediated by lectin-sugar bindings, the glycoconjugates of the surfaces of M cells and enterocytes were compared.

Methods: A set of 28 lectins and corresponding sugars was used for light and electron microscopy of fixed and unfixed sections. M cells were identified by anti-vimentin antibodies.

Results: M cells of the cecal lymphoid patches selectively bound lectins specific for fucose or N-acetylgalactosamine. The labeled glycoconjugates were located in the apical membrane and in the membrane of vesicles in the apical cytoplasm. Enterocytes were selectively labeled by galactose-specific lectins. In contrast, the lectin-reactivity of M cells and enterocytes did not differ in the jejunal Peyer's patches.

Conclusions: The results suggest that there may be selectivity mediated by glycoconjugates in the uptake of antigenic material by cecal M cells but not by jejunal M cells.