Colonization of Helicobacter pylori in the stomach leads to chronic gastritis with massive infiltration by Th1 cells. To assess a role played by those T cells in the remodeling of gastric epithelium, we activated gastric T cells utilizing mice with CD4 T cells bearing transgenic TCR with or without deficiency in either IL-4 or IFN-gamma or IL-12. Mice developed gastritis upon injection of an antigen into gastric mucosa. While neutrophil infiltration occurred even with a control antigen, infiltration by transgenic T cells was dependent on the specific antigen. The numbers of epithelial cells undergoing apoptosis and regeneration were increased in the mice with infiltrating T cells producing IFN-gamma and the alignment of those cells in the glands was markedly dysregulated. In contrast, mice deficient in Th1 response showed no increase in cell division and apoptosis of epithelial cells. Thus, Th1 type T cells infiltrating into gastric mucosa play an independent role in controlling turnover of epithelial cells. (C) 2004 Elsevier Inc. All rights reserved.