Analysis of cytokines in the early development of gastric secondary lymphoid follicles in Helicobacter pylori-infected BALB/c mice with neonatal thymectomy

Immunological interaction between the host and Helicobacter pylori seems to play a critical role in follicular formation in gastric mucosa. We reporte d H. pylori-induced follicular gastritis model using neonatally thymectomiz ed mice. In this study, we investigated the involvement of various cytokine s in this model. BALB/c mice were thymectomized on the third day after birt h (nTx). At 6 weeks old, these mice were orally infected with H. pylori. Hi stological studies showed that follicular formation occurred from 8 weeks a fter the infection and that most of the infiltrating lymphocytes were CD4() and B cells. Neutrophils increased transiently at I week after the infect ion. Gamma interferon, interleukin-7 (IL-7), and IL-7 receptor were express ed in the stomach of the nTx mice irrespective of the infection. In contras t, expressions of the tumor necrosis factor alpha, IL-4 and lymphotoxin-a. genes were remarkably upregulated by the infection. Our findings suggest th at follicular formation may require cooperative involvement of a Th2-type i mmune response, tumor necrosis factor alpha and lymphotoxin-a in addition t o the Th1-type immune response in H. pylori-induced gastritis in nTx mice.