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 CD19^low, 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, CD3^high T cells and CD45RO^high 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 CD56^high, memory T‐cell subset with CD4^high, and naive, memory, memory/effector, and effector T‐cell subsets with CD8^high (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.