Abstract
In this study we analyzed whether infection with Helicobacter pylori gives rise to specific B-cell responses against a number of putative virulence factors of H. pylori, e.g., urease, flagellin, and different bacterial surface antigens, locally in the gastric mucosa. This was studied in antrum and corpus biopsies collected from 11 H. pylori-infected patients with duodenal ulcers, 11 asymptomatic H. pylori carriers, and 13 noninfected, healthy controls. Mononuclear cells were isolated from the biopsies and assayed for frequencies of total and H. pylori-specific antibody-secreting cells (ASCs) by means of the enzyme-linked immunospot technique. The H. pylori-infected subjects had remarkably higher frequencies of total immunoglobulin A (IgA)- and IgM-secreting cells than the noninfected subjects, while the frequencies of IgG-secreting cells were virtually the same in the different groups. In addition, most of the infected subjects had IgA ASCs reacting with H. pylori membrane proteins, flagellin, and urease, while none of the noninfected subjects had any detectable H. pylori-reactive ASCs. Furthermore, half of the infected subjects also had ASCs reacting with a Helicobacter-specific 26-kDa protein, while only a few of them had ASCs reacting with neutrophil-activating protein, the neuraminyllactose-binding hemagglutinin HpaA, or lipopolysaccharides purified from different H. pylori strains. The frequencies of H. pylori-specific ASCs in the antrum and corpus were almost identical, and no differences in either antigen specificity or magnitude of the B-cell response in the stomach could be detected between the ulcer patients and the asymptomatic H. pylori carriers. This study demonstrates that H. pylori infection induces strong antibody responses in the human gastric mucosa, both in asymptomatic carriers and in duodenal ulcer patients. However, the outcome of infection could not be explained by differences in the local B-cell response to any of the antigens used in this study.