CD69 and infection: Figure 3 shows that CD69 was significantly up-regulated by CD3+ cells co-cultured with live bacteria, but not with killed bacteria. These data show that H. pylori driven T lymphocytes activation occurred in the absence of APCs, and suggest that this effect was independent of their antigen specificity. Moreover, we also found that the T cell responsiveness was not increased when we used PBMCs from H. pylori positive subjects (supplementary materials Figure S1). This suggests that the activation mechanism is not antigen-specific, and it does not depend on previous infections with H. pylori.