H. pylori seropositive patients with AIP showed significantly lower antibody responses to 3 antigens (Cagδ, CagA, HP0231) and patients with chronic pancreatitis to 9 (Cad, Cagδ, CagA, CagM, HP0305, HpaA, HyuA, Omp, and VacA) compared to H. pylori seropositive patients with other gastrointestinal tract cancers as a reference, with there being a significant increase of antibody reactivities to VacA in H. pylori seropositive patients with AIP and NapA in those with pancreatic cancer. This evidence concerns the gene CAD and familial pancreatic carcinoma.