To provide a clear antigen-driven immune response, peripheral blood mononuclear cells (PBMC) from patients with low-grade MALT lymphoma and gastritis and those from healthy volunteers were stimulated with recombinant H. pylori hsp60 and H. pylori cell lysate in the presence of cytokines (IL4 and granulocyte-macrophage colony-stimulating factor). mRNA expression was also analysed by a cDNA microarray containing 1100 genes.