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

OBJECTIVE: 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.
METHODS: 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.
RESULTS: 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.
CONCLUSIONS: 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.