An increased number of follicles containing activated CD69+ helper T cells and proliferating CD71+ B cells are found in H. pylori-infected gastric mucosa.

Abstract

An immune response occurring in Helicobacter pylori-infected gastric mucosa could have a direct implication for associated pathologies. In the present study we analyzed the expression of the immune activation, proliferation, and phenotype markers by immune cell subpopulations in H. pylori-infected and uninfected gastric samples. Antral gastric biopsies from both H. pylori-positive and -negative patients were processed by immunohistochemistry; gastric epithelial cells were isolated from biopsy tissue and analyzed by flow cytometry. Ten of the 13 biopsies that contained follicles were H. pylori positive. Follicular CD69 was expressed mainly by CD4+ T cells and the central core of follicles showed double immunopositivity for the B-cell marker CD19 and transferrin receptor. Also detected was an increase in the percentage of epithelial cells from H. pylori-positive samples expressing HLA-DR and beta2 microglobulin, compared to negative samples (61 +/- 15% vs 9 +/- 9%, p = 0.003 and 93 +/- 7% vs 52 +/- 18%, p = 0.002, respectively), whereas no variation on class I HLA was detected. These results suggest that chronic H. pylori infection could facilitate the persistence of follicles on which continuous follicular helper T-cell activation could lead to uncontrolled follicular B-cell proliferation. Furthermore, beta2 microglobulin expression by epithelial cells in a nonparallel way to class I HLA may indicate the possibility of nonclassical class I MHC expression on the basal surface of the epithelium.