Pediatric Helicobacter pylori Infection and Circulating T-Lymphocyte Activation and Differentiation

Background:  In this study, H. pylori-infected and noninfected children with gastritis were compared to a control group with respect to circulating CD4+ and CD8+ T lymphocytes expressing activation and differentiation markers. Additionally, the lymphocyte phenotypes of children with gastritis were correlated with the gastric inflammation scores. Materials and Methods: H. pylori infection status was assessed based on [13C]urea breath test, rapid urease test, and histology. Analysis of the lymphocyte surface molecule expression was carried out by triple-color flow cytometry. Results:  The group of H. pylori-infected children showed an elevated proportion of peripheral B cells with CD19low, along with a twofold increase in the percentage of memory (CD45RO+) CD4+ and CD8+ T-cell subsets (p < .05). Moreover, a positive correlation between the age and the percentage of these subsets was seen (r = .38, p = .04 and r = .56, p < .01, respectively). Children with gastritis but without infection had a slightly increased percentage of CD8+ T cells and CD56+ NK cells, CD3high T cells and CD45ROhigh CD4+ T-cell subsets (p < .05). Both H. pylori-infected and noninfected children with gastritis were characterized by an increased percentage of memory/effector CD4+ T cells, the presence of NK cells with CD56high, memory T-cell subset with CD4high, and naive, memory, memory/effector, and effector T-cell subsets with CD8high (p < .05). Gastric inflammation scores correlated positively with the percentage of CD4+ T lymphocytes in H. pylori-infected children (r = .42, p = .03). In noninfected children, gastric inflammation scores correlated positively with the percentage of B cells (r = .45, p = .04). Conclusion:  In H. pylori-negative children, gastritis was associated with an increased percentage of activated NK and T cells, and intermediate-differentiated peripheral blood CD4+ T cells, which was more pronounced in H. pylori-positive children who also showed an increased B-cell response. However, increased inflammation was only associated with the elevation of CD4+ T-cell percentage in H. pylori-positive children as well as B-cell percentage in H. pylori-negative children with gastritis.