Subsequent sections from the paraffin blocks were prepared and stained by modified Giemsa. Immunostaining for H. pylori was done as described. In short, tissue sections were deparaffinized in xylene, rehydrated through decreasing concentrations of alcohol ending in phosphate-buffered saline (PBS), and subjected to pretreatment with Proteinase K (8 minutes). The sections were quenched with 3% hydrogen peroxidase, incubated with protein block for 15 minutes at room temperature, and washed in PBS. Tissues then were incubated with polyclonal rabbit anti-H pylori antibody (dilution, 1:10; clone ch-20 429, DAKO, Carpinteria, CA). Finally, sections were washed in 0.05% polysorbate 20 in PBS, pH 7.4, and the bound antibody was detected using streptavidin and biotinylated secondary antibody with diaminobenzidine as the chromogen. Sections were counterstained with hematoxylin, dehydrated, and mounted. Negative controls were sections treated as above, but instead of incubation with the primary antibody, they were incubated with 1% bovine serum albumin in PBS.