It has been suggested that the dependence of low grade B cell gastric lymphoma on infection of the gastric mucosa with Helicobacter pylori results from help provided by H pylori specific tumour infiltrating T cells. ELISpot analysis was used to characterise functional subpopulations of tumour infiltrating T cells. The production of the TH1 cytokine interferon gamma and TH2 cytokines interleukin (IL)-4, IL-5, and IL-10 were measured in tumour cell suspensions.