Natural killer cell receptor⁺ T-lymphocytes in normal and Helicobacter pylori-infected human gastric mucosa

Background: Helicobacter pylori infection is associated with development of chronic inflammation and infiltration of immune cells into the gastric mucosa. As unconventional T-lymphocytes expressing natural killer cell receptors are considered to play central roles in the immune response against infection, a study investigating their frequencies in normal and H. pylori-infected gastric mucosa was undertaken. Materials and Methods: Flow cytometry was used to quantify T-cells expressing the natural killer cell markers CD161, CD56, and CD94 in freshly isolated lymphocytes from the epithelial and lamina propria layers of gastric mucosa. Thirteen H. pylori-positive and 24 H. pylori-negative individuals were studied. Results: CD94⁺ T-cells were the most abundant (up to 40%) natural killer receptor-positive T-cell population in epithelial and lamina propria layers of H. pylori-negative gastric mucosa. CD161⁺ T-cells accounted for about one-third of all T-cells in both compartments, but the lowest proportion were of CD56⁺ T-cells. Compared with H. pylori-negative mucosa, in H. pylori-infected mucosa the numbers of CD161⁺ T-cells were significantly greater (p =.04) in the epithelium, whereas the numbers of CD56⁺ T-cells were lower (p =.01) in the lamina propria. A minor population (< 2%) of T-cells in both mucosal layers of H. pylori-negative subjects were natural killer T-cells, and whose proportions were not significantly different (p >.05) to those in H. pylori-infected individuals. Conclusions: The predominance, heterogeneity, and distribution of natural killer cell receptor-positive T-cells at different locations within the gastric mucosa reflects a potential functional role during H. pylori infection and warrants further investigation.