Helicobacter heilmannii can induce gastric lymphoid follicles in mice via a Peyer's patch-independent pathway

Helicobacter heilmannii induces gastric lymphoid follicles in mice. However, the pathogenic mechanisms behind the induction of gastric lymphoid follicles by H. heilmannii infection have not been elucidated. The aim of this study was to investigate the roles of Peyer's patches (PP) in H. heilmannii-induced immune responses and the development of gastric lymphoid follicles. C57BL/6J and PP deficient mice were infected with H. heilmannii, and in addition to histological and immunohistological examinations, the expression levels of cytokines and chemokines in gastric mucosa were investigated. Gastric lymphoid follicle formation and the infiltration of dendritic cells, B cells, and helper T cells were milder in the PP-deficient mice 1 month after infection, but they were similar in both types of mice after 3 months. The mRNA expression levels of tumor necrosis factor alpha and CC chemokine ligand 2 were significantly high in the H. heilmannii-infected groups, and CXC chemokine ligand 13 expression was significantly increased in the infected C57BL/6J wild-type mice 1 month after infection. These results suggest that PP are not essential for the formation and development of gastric lymphoid follicles induced by H. heilmannii infection, although they are involved in the speed of gastric lymphoid follicle formation.