Phenotypic evaluation of natural killer (NK) and natural killer T (NKT)-like cells in patients with peptic ulcer and gastric cancer caused by Helicobacter pylori infection

Background and The aim of this study was to compare the proportion of natural killer (NK) and natural killer T (NKT)-like cells in dyspeptic disorders caused by Helicobacter pylori (H. pylori). In a case-control study, 27 patients with gastric cancer (GC), 25 patients with peptic ulcer (PUD), and 22 patients with non-ulcer dyspepsia (NUD) were enrolled. After endoscopic diagnosis, the proportions of NK cells subsets (CD3-CD56+ and CD3-CD16+), as well as NKT-like cells (CD3+CD56+) in peripheral blood were determined by flow cytometry. The frequency of CD8+ and CD8– NK cell subsets were also determined. H. pylori infection was confirmed in all study subjects using the rapid urease test and histopathology. The frequencies of CD3-CD16+ NK, CD3-CD56+ NK, and CD3+CD56+ NKT-like cells in patients with gastric cancer infected by H. pylori were significantly lower than those in patients with non-ulcer dyspepsia (P < 0.001, P = 0.050, and P = 0.020, respectively). However, these cell populations showed no significant difference between the PUD and NUD groups. Further analysis showed that high numbers of CD8– NK cells in the blood were CD56+ and CD16+ phenotypes. This study showed decreased numbers of NK and NKT-like cell populations in patients with gastric cancer compared to those with non-ulcer dyspepsia. It is thus suggested that these cells may limit the prolonged inflammation by H. pylori, which, in turn, reduce the risk of gastric cancer.