Article

Natural killer (NK) cells in antibacterial innate immunity: angels or devils?

Institut Pasteur, Cytokines and Inflammation Unit, Department of Infection and Epidemiology, Paris, France.
Molecular Medicine (Impact Factor: 4.51). 11/2011; 18(1):270-85. DOI: 10.2119/molmed.2011.00201
Source: PubMed

ABSTRACT

Natural killer (NK) cells were first described as immune leukocytes that could kill tumor cells and soon after were reported to kill virus-infected cells. In the mid-1980s, 10 years after their discovery, NK cells were also demonstrated to contribute to the fight against bacterial infection, particularly because of crosstalk with other leukocytes. A wide variety of immune cells are now recognized to interact with NK cells through the production of cytokines such as interleukin (IL)-2, IL-12, IL-15 and IL-18, which boost NK cell activities. The recent demonstration that NK cells express pattern recognition receptors, namely Toll-like and nucleotide oligomerization domain (NOD)-like receptors, led to the understanding that these cells are not only under the control of accessory cells, but can be directly involved in the antibacterial response thanks to their capacity to recognize pathogen-associated molecular patterns. Interferon (IFN)-γ is the predominant cytokine produced by activated NK cells. IFN-γ is a key contributor to antibacterial immune defense. However, in synergy with other inflammatory cytokines, IFN-γ can also lead to deleterious effects similar to those observed during sepsis. Accordingly, as the main source of IFN-γ in the early phase of infection, NK cells display both beneficial and deleterious effects, depending on the circumstances.

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    • "Human natural killer (NK) cells are considered professional cytotoxic cells integrated into the effector branch of innate immunity during antiviral [1], antitumoral [2], antimicrobial [3], and antiparasitic [4] responses and also exert regulatory effects on innate and adaptive immunity through various cytokines and chemokines or cell-to-cell-dependent contacts [5]. This immunoregulatory function is attributed mostly to CD56 bright NK cells that are characterized by high CD56 expression [6], while CD56 dim NK cells have the most evident cytotoxic properties [7– 9]. "
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    ABSTRACT: 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-b 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-b+ NK cells in breast cancer patients which might impair efficiency of anti-tumor immunity.
    Full-text · Dataset · Nov 2015
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    • "Human natural killer (NK) cells are considered professional 49 cytotoxic cells integrated into the effector branch of innate 50 immunity during antiviral [1], antitumoral [2], antimicrobial [3], 51 and antiparasitic [4] responses and also exert regulatory effects 52 on innate and adaptive immunity through various cytokines and 53 chemokines or cell-to-cell-dependent contacts [5]. This immuno- 54 regulatory function is attributed mostly to CD56 bright NK cells that 55 are characterized by high CD56 expression [6], while CD56 dim NK 56 cells have the most evident cytotoxic properties [7] [8] [9]. "

    Full-text · Dataset · Sep 2015
  • Source
    • "Human natural killer (NK) cells are considered professional cytotoxic cells integrated into the effector branch of innate immunity during antiviral [1], antitumoral [2], antimicrobial [3], and antiparasitic [4] responses and also exert regulatory effects on innate and adaptive immunity through various cytokines and chemokines or cell-to-cell-dependent contacts [5]. This immunoregulatory function is attributed mostly to CD56 bright NK cells that are characterized by high CD56 expression [6], while CD56 dim NK cells have the most evident cytotoxic properties [7– 9]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: 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.
    Full-text · Article · Sep 2015 · Cellular Immunology
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