INTERNALIZATION OF HELICOBACTER-PYLORI BY EPITHELIAL-CELLS - THE KEY TO THE INFLAMMATORY RESPONSE TO HELICOBACTER-PYLORI INFECTION

Objective. To better understand the pathogenesis of the intense humoral and cellular response to Helicobacter pylori infection. Design. The mechanism of the uptake of H. pylori into epithelial cells was studied in vitro, using four strains of H. pylori and two different cultured cells. Methods. H. pylori were grown on blood agar. They were counted visually after staining and by colony-forming units of viable bacteria grown with and without gentamicin. Adherence assays were performed with Y-1 mouse adrenal cells and HEp-2 cells grown in 24-cell tissue-culture plates under 12-mm coverslips. To assay viable bacteria, the tissue-culture cells were washed, lysed, and the lysate cultured. The location (attached extracellular versus intracellular) was determined by gentamicin sensitivity and electron microscopy. Results. Isolates of H. pylori enter into the cytoplasm of tissue-culture epithelial cell lines such as HEp-2 cells. The intracellular uptake of H. pylori by HEp-2 cells is rapid and appears to require both the N-acetylneuraminyllactose-binding adhesin and another factor present only in living bacteria. Internalization of H. pylori was inhibited by ammonium chloride and chloroquine at concentrations which did not affect either adherence or bacterial viability. The internalization was completely inhibited when H. pylori and HEp-2 cells were incubated at 4-degrees-C under conditions which did not affect bacterial adherence. Conclusion. Internalization of H. pylori may be the key event that provokes a sustained immune response.