AIM: To investigate and elucidate the molecular mechanism that regulates inducible expression of CD69 by Helicobacter pylori (H. pylori ) infection. METHODS: The expression levels of CD69 in a T-cell line, Jurkat, primary human peripheral blood mononuclear cells (PBMCs), and CD4 + T cells, were assessed by immunohistochemistry, reverse transcription polymerase chain reaction, and flow cytometry. Activation of CD69 promoter was detected by reporter gene. Nuclear factor (NF)-κB activation in Jurkat cells infected with H. pylori was evaluated by electrophoretic mobility shift assay. The role of NF-κB signaling in H. pylori-induced CD69 expression was analyzed using inhibitors of NF-κB and dominant-negative mutants. The isogenic mutants with disrupted cag pathogenicity island (cag PAI) and virD4 were used to elucidate the role of cag PAI-encoding type Ⅳ secretion system and CagA in CD69 expression.RESULTS: CD69 staining was detected in mucosal lymphocytes and macrophages in specimens of pa- tients with H. pylori-positive gastritis. Although cag PAI- positive H. pylori and an isogenic mutant of virD4 induced CD69 expression, an isogenic mutant of cag-PAI failed to induce this in Jurkat cells. H. pylori also induced CD69 expression in PBMCs and CD4 + T cells. The activation of the CD69 promoter by H. pylori was mediated through NF-κB. Transfection of dominant-negative mutants of IκBs, IκB kinases, and NF-κB-inducing kinase inhibited H. pylori-induced CD69 activation. Inhibitors of NF-κB suppressed H. pylori-induced CD69 mRNA expression. CONCLUSION: The results suggest that H. pylori induces CD69 expression through the activation of NF-κB. cagPAI might be relevant in the induction of CD69 expression in T cells. CD69 in T cells may play a role in H. pylori-induced gastritis. AIM: To investigate and elucidate the molecular mechanism that regulates inducible expression of CD69 by Helicobacter pylori (H. pylori) infection. METHODS: The expression levels of CD69 in a T-cell line, Jurkat, primary human peripheral blood mononuclear cells (PBMCs) , and CD4 + T cells, were assessed by immunohistochemistry, reverse transcription polymerase chain reaction, and flow cytometry. Activation of CD69 promoter was detected by reporter gene. Nuclear factor (NF) -κB activation in Jurkat cells infected with H. pylori was evaluated The role of NF-κB signaling in H. pylori-induced CD69 expression was analyzed using inhibitors of NF-κB and dominant-negative mutants. The isogenic mutants with disrupted cag pathogenicity island (cag PAI) and virD4 were used to elucidate the role of cag PAI-encoding type IV secretion system and CagA in CD69 expression .RESULTS: CD69 staining was detected in mucosal lymphocytes and macrophages in specimens of c-PAI-positive H. pylori and an isogenic mutant of virD4-induced CD69 expression, an isogenic mutant of cag-PAI failed to induce this in Jurkat cells. H. pylori also induced CD69 expression in PBMCs and CD4 + T cells. The activation of the CD69 promoter by H. pylori was mediated through NF-κB. Transfection of dominant-negative mutants of IκBs, IκB kinases, and NF-κB-inducing kinase inhibited H. pylori -induced CD69 activation. Inhibitors of NF-κΒ suppressed H. pylori-induced CD69 mRNA expression. CONCLUSION: The results suggest that H. pylori induces CD69 expression through the activation of NF-κB. cagPAI might be relevant in the induction of CD69 expression in T cells. CD69 in T cells may play a role in H. pylori-induced gastritis.