The putative role of members of the CEA-gene family (CEA, NCA an BGP) as ligands for the bacterial colonization of different human epithelial tissues.

Immobilized purified CEA (carcinoembryonic antigen), NCA (non-specific crossreacting antigen) and BGP I (biliary glycoprotein I) bind strains of E. coli (including EPEC) and some Salmonella species (including S. typhi, S. paratyphi A + B and S. java) while Shigella-, Yersinia- and Bacteroides- strains showed no adhesion. The binding was of high avidity, heat sensitive, dose dependent, saturable and nearly completely abolished in the presence of 10 mM alpha-methylmannoside. From inhibition studies with aromatic mannose compounds, it was suggested that in contrast to Salmonella strains E. coli strains exhibit a higher hydrophobicity in the binding region adjacent to the CEA-, NCA- and BGP-binding site. By further inhibition experiments it could be demonstrated that E. coli and Salmonella strains bind to high-mannose type oligosaccharides of these molecules via lectins on bacterial type I fimbriae. We conclude that the expression of products of this gene family on different human epithelial cells (colon-, bile canaliculi, uroepithel etc.) may function as ligands for bacterial colonization of epithelial tissues.