CD4(+) and CD8(+) T cell responses in Helicobacter pylori-infected individuals

In order to characterize T cell responses in human Helicobacter pylori infe ction, we have examined proliferative responses and cytokine production by CD4(+) and CD8(+) T cells isolated from duodenal ulcer patients and asympto matic H. pylori carriers, after activation with some H. pylori antigens tha t may be important in disease development. For control purposes, T cells fr om uninfected volunteers were also examined. The different H. pylori antige ns induced only modest proliferative responses in circulating CD4(+) and CD 8(+) T cells from both H. pylori-infected and uninfected individuals. Howev er, circulating T cells from H. pylori-infected subjects produced larger am ounts of interferon-gamma (IFN-gamma) in response to the Helicobacter antig ens than did T cells from uninfected volunteers. Furthermore, CD8(+) T cell s produced larger amounts of IFN-gamma than did CD4(+) T cells, on a per ce ll basis. Most IFN-gamma -producing cells from both infected and uninfected volunteers appeared to be naive T cells expressing CD45RA. Increased produ ction of IL-4 and IL-5 was, on the other hand, only seen in a few instances after stimulation of isolated CD4(+) and CD8(+) T cells. Stimulation of fr eshly isolated gastric T cells with the different H. pylori antigens did no t result in increased proliferation or cytokine production. In conclusion, our results show that several different purified H. pylori antigens induce production of IFN-gamma, preferentially by CD8(+) cells. Therefore, they su ggest that IFN-gamma -secreting CD8(+) cells contribute significantly to th e cytokine response induced by H. pylori infection.