HELICOBACTER PYLORI-SPECIFIC TUMOR-INFILTRATING T-CELLS PROVIDE CONTACT-DEPENDENT HELP FOR THE GROWTH OF MALIGNANT B-CELLS IN LOW-GRADE GASTRIC LYMPHOMA OF MUCOSA-ASSOCIATED LYMPHOID-TISSUE

Previous studies have shown that tumour cells from low-grade B-cell ga stric lymphomas of mucosa-associated lymphoid tissue (MALT) type proli ferate in vitro in response to heat-killed whole cell preparations of Helicobacter pylori, but only in the presence of tumour-infiltrating T cells. This response is strain-specific in that the tumours studied r esponded optimally to different strains of H. pylori. It was unclear f rom these studies, however, whether the ability to recognize the speci fic stimulating strains of H. pylori was a property of the tumour cell s or the tumour-infiltrating T cells. This study shows that whereas th e tumour cells do not respond to H. pylori, both freshly isolated tumo ur-infiltrating T cells and a T cell line derived from these cells pro liferate in response to stimulating strains of H. pylori. T cells from the spleen of one of the patients do not share this property. These r esults suggest that B-cell proliferation in cases of low-grade gastric lymphoma of MALT type in vitro in response to H. pylori is due to rec ognition of H. pylori by tumour-infiltrating T cells, which in turn pr ovide help for tumour cell proliferation. The observations provide an explanation for properties of gastric MALT-type lymphoma, such as regr ession following eradication of N. pylori and the tendency of the tumo ur to remain localized to the primary site.