Mucosal humoral immune response to CagA shows a high prevalence in patients with gastric MALT-type lymphoma.

In the pathogenesis of gastric mucosa-associated lymphoid tissue (MALT)-type lymphoma, CagA-positive Helicobacter pylori strains have been suspected of making a significant contribution. To investigate this hypothesis in more detail, the mucosal humoral immune response of 15 patients with gastric MALT-type lymphoma was examined in the tumor and in the tumor-free gastritis of the same patient. Mononuclear cells from different sites (antrum, corpus, lymphoma) were cultured. Culture supernatant and serum of the same patient were used for immunodetection of CagA. All patients displayed an immune response to CagA in the tissue-culture supernatants. Although the humoral immune response in the tumor was restricted to a very few H. pylori antigens, antibodies directed against CagA protein were found in most patients. The immune response to CagA in nearly all lymphoma patients--not only in the serum, but also in the mucosa, including the tumor site--support the hypothesis that CagA is involved in the pathogenesis of gastric MALT-type lymphoma.