ABSTRACT
The luminal plasma membrane of intestinal absorptive cells displays a rich and heterogeneous array of glycoconjugates. Although the exact arrangement of specific integral and peripheral membrane glycoproteins in the intestinal cell “glycocalyx” is not known, it is well established that these cell surface oligosaccharides provide a variety of potential binding sites for bacterial toxins, microorganisms, and experimental ligands such as plant lectins. It is clear that mutual bacterial and intestinal cell “recognition” and adhesion is a prerequisite both for invasion and for the formation of stable attachment sites. Mutual recognition of cell-specific surface macromolecules is also the initial event in the association of embryonic cells during tissue assembly. The unique position of the intestinal epithelial cell would make the routine endocytosis of luminal membrane a risky activity, with the inherent danger of incorporating opportunistic, foreign luminal ligands, and organisms along with the internalized membrane.
