Dendritic cells are potent antigen-presenting cells that are present in the gastrointestinal tract and are required for the induction of a Th1 T-cell acquired immune response. Since infection with the gastric pathogen Helicobacter pylori elicits a Th1 cell response, the interaction of these organisms with dendritic cells should reflect the Th1 bias. We incubated H. pylori with cultured human dendritic cells and measured the cytokine induction profile, comparing the response to that induced by Salmonella enterica serovar Typhimurium. We found that H. pylori induced little interleukin 6 (IL-6) and essentially no IL-10 in contrast to S. enterica. However, H. pylori induced levels of IL-12 that were 30% of those induced by S. enterica, indicating a Th1 response. An isogenic cagE mutant of H. pylori lost about 50% of its IL-12-inducing ability, suggesting a role for the cag type IV secretion system in the stimulation of dendritic cells.