Using molecular methods (multiplex [MP]-PCR, RT-PCR) and a micro ELISPOT assay on peripheral blood mononuclear cells (PBMCS), Th1, Th2, Th3 or balanced Th1/Th2 response will be determined to further characterize the Hp-infected child's immune response phenotype. The investigators propose to further their previous work with critically lacking studies from a multivariate approach, leading to a better understanding of the gastroduodenal disease sequelae and overall pathobiology of Hp infection in humans.