ADHESION OF HELICOBACTER-PYLORI TO POLARIZED T-84 HUMAN INTESTINAL-CELL MONOLAYERS IS PH DEPENDENT

Epithelial cells, which form tight polarized monolayers on porous subs trates, constitute ideal model systems to study bacterial adhesion and invasion. The binding of Helicobacter pylori to the apical membrane o f T-84 cells, an epithelial cell line derived from a human colon carci noma, was assessed biochemically and morphologically. Attachment was r apid, and binding remained constant over time, with a significant (P < 0.01, Mann-Whitney U test) ca. fourfold increase at pH 5.4 (76% +/- 2 2%) compared with pH 7.4 (18% +/- 7%). In contrast, adhesion of entero pathogenic Escherichia coli was not enhanced at pH 5.4. The transepith elial electrical resistance of the T-84 cell monolayers was not affect ed by pH or by H. pylori. Following binding, H. pylori induced a reorg anization of the brush border as reflected by actin condensation, faci litating the intimate association of the bacteria with the apical plas ma membrane. H. pylori was not internalized, as shown by confocal micr oscopy. Some bacteria, found in deep invaginations of the apical membr ane, were probably inaccessible to gentamicin, thus accounting for the observed tolerance to the antibiotic. These data provide the first ev idence that an acidic environment favors Helicobacter adhesion and tha t binding is followed by survival of the bacteria in pockets of the ap ical membrane.