Immunophenotype of peripheral blood natural killer cells and IL‐10 serum levels in relation to Helicobacter pylori status

Recent findings suggest that NK (Natural Killer) cells may directly modulate the antimicrobial immune responses. In this study, we performed immunophenotypic analysis of peripheral blood NK cells with regard to CD56, CD16, Nkp46, and CD25 markers, as well as IL‐10 levels quantification in the sera samples of asymptomatic, H. pylori (Hp)‐infected or uninfected individuals, and combined these results with our previous findings on lymphocyte cytotoxic activity. Twenty healthy volunteers [10 Hp(?);10 Hp(+)] were included in the study. The percentages of classic lymphocytes (CD3⁺) and NK cells (CD3^?CD56⁺, CD3^?Nkp46⁺, CD3^?CD16⁺) with or without CD25 receptor were evaluated by fluorochrome‐conjugated monoclonal antibody staining and flow cytometry analysis. IL‐10 quantification was performed by enzyme‐linked immunosorbent assay‐ELISA. Our study showed elevated levels of IL‐10 and higher NK cell numbers of both CD3^?CD56⁺CD25⁺ and CD3^?Nkp46⁺CD25⁺ phenotypes, as well as CD3⁺CD25⁺ classic lymphocytes in Hp(+) compared with Hp(?) individuals. No differences between Hp(?) and Hp(+) individuals were found either in total number of classic lymphocytes or NK cell subtypes. Our data suggest that in Hp(+) donors, there is a domination of lymphocytes and NK cells co‐expressing CD25 marker, which might be influenced by the regulatory IL‐10. This phenomenon may be a result of H. pylori adaptation to a changing environment in vivo leading to a chronic infection and lack of severe gastric pathologies.