Peripheral blood NK cells expressing HLA-G, IL-10 and TGF-β in healthy donors and breast cancer patients

Human natural killer (NK) cells are not only professional cytotoxic cells integrated into effector branch of innate immunity, but they are also regulatory cells, managing different immune processes. Immunoregulatory NK cells, expressing HLA-G and IL-10, have been generated in vitro from human hematopoietic progenitors and found in vivo among decidual NK cells of pregnant women. Human peripheral blood NK cells have been shown to acquire suppressive properties after HLA-G uptake during trogocytosis. Moreover, it has been shown that circulating NK cells contain a trace amount of cells producing TGF-β and IL-10, which exert a suppressive influence upon innate and adaptive immunity. In this study, we report on a minor subset of peripheral blood HLA-G+ NK cells possessing suppressive activity toward effector functions of NK cells. Further we demonstrate an increased number of circulating HLA-G+, IL-10+, and TGF-β+ NK cells in breast cancer patients which might impair efficiency of anti-tumor immunity.