Background & Aims: Immune responses to Helicobacter pylori are important in the pathogenesis of gastric mucosa-associated lymphoid tissue (MALT) lymphoma. In this retrospective case study, we investigated whether certain alleles and haplotypes of major histocompatibility complex genes are associated with gastric MALT lymphoma and the efficacy of H pylori eradication therapy on the lymphoma. Methods: Blood samples were obtained from 18 patients with H pylori-positive gastric MALT lymphoma (5 men and 13 women; age range, 51-80 years), 30 patients with H pylori-positive non-ulcer dyspepsia (17 men and 13 women; age range, 37-77 years), and 30 patients with H pylori-negative non-ulcer dyspepsia (12 men and 18 women; age range, 37-77 years). HLA-DQA1 and DQB1 allele typing was performed by use of a polymerase chain reaction sequence-specific oligonucleotide procedure. All patients with MALT lymphoma were treated with H pylori eradication therapy and followed up by repeated endoscopy and biopsy. Results: We found a significant increase in alleles HLA-DQA1*0103 and HLA-DQB1*0601, and a haplotype DQA1*0103-DQB1*0601, in MALT lymphoma patients when compared with non-ulcer dyspepsia patients who were either H pylori-positive or not and with a healthy control population. After H pylori eradication, the lymphomas regressed completely in all 10 patients who possessed the DQA1*0103-DQB1*0601 haplotype but in only 4 of the 8 without this haplotype (P = .023). Conclusions: DQA1*0103-DQB1*0601 haplotype-positive gastric MALT lymphoma is likely to respond to therapy by eradication of H pylori.
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