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Adaptive Natural Killer Cells Integrate Interleukin-18 during Target-Cell Encounter.

ABSTRACT: Human cytomegalovirus (HCMV) infection induces adaptations in the natural killer (NK)-cell compartment. Expanded subsets of adaptive NK cells display potent effector functions against cellular targets, despite their apparent unresponsiveness to stimulation with classical dendritic cell-derived cytokines interleukin (IL)-12 and IL-18. However, it remains unclear whether adaptive NK cells have completely lost their ability to sense inflammation via IL-12 and IL-18 or whether these pro-inflammatory signals can be functionally integrated into defined contexts. Here, we demonstrate that adaptive NKG2C+ NK cells can be costimulated by the presence of pro-inflammatory cytokines during target cell-induced activation. Cytokine costimulation of adaptive NK cells resulted in elevated interferon (IFN)-gamma and tumor necrosis factor (TNF) production, which promoted protein expression of HLA class I and adhesion molecules as well as transcription of genes involved in antigen processing and antiviral states in endothelial bystander cells in vitro. We further show that IL-18 drove costimulation in functional assays and was sufficient for elevated cytokine production in the absence of IL-12. Hence, adaptive NKG2C+ NK cells-although poorly responsive to IL-12 and IL-18 as an isolated stimulus-integrate IL-18 as a costimulatory signal during target-cell encounter.

SUBMITTER: Hammer Q

PROVIDER: S-EPMC5776097 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:ObjectiveSystemic juvenile idiopathic arthritis (sJIA) is characterized by fever, arthritis, rash, hepatosplenomegaly, and macrophage activation syndrome; however, its pathogenesis is still unclear. Elevated serum interleukin (IL)-18 concentrations and decreased natural killer (NK) cell activity are characteristic of active disease; thus, we examined IL-18 signaling in NK cells from sJIA.MethodsWe analyzed mitogen-activated protein kinase (MAPK) p38 and nuclear factor κ light chain enhancer of activated B cells (NFκB) p65 phosphorylation in NK cells after in vitro recombinant IL-18 (rIL-18) stimulation in 31 patients with sJIA. Associations between clinical features, serum IL-18, and phosphorylation intensity were analyzed. Furthermore, we investigated the effects of high IL-18 concentrations on phosphorylation in NK cells.ResultsPatients were divided according to their disease activity: systemic features (n = 8), chronic arthritis (n = 7), remission on medication (n = 10), and remission off medication (n = 6). MAPK p38 and NFκB p65 phosphorylation intensity were the highest in healthy controls, followed by remission off medication, remission on medication (vs. control; MAPK p38, P < 0.01; NFκB p65, P < 0.05), chronic arthritis (P < 0.001, P < 0.001), and systemic features (P < 0.001, P < 0.001). The systemic features group showed a complete defect in phosphorylation. Serum IL-18 was the highest in the systemic features group followed by chronic arthritis, remission on medication (P < 0.01), remission off medication (P < 0.01), and healthy controls (P < 0.01). Phosphorylation intensity was negatively correlated with serum IL-18 (MAPK p38, r2 = 0.42; NFκB p65, r2 = 0.54). Furthermore, healthy control NK cells were cultured with rIL-18; impaired phosphorylation was reproduced in vitro.ConclusionImpaired IL-18 signaling in NK cells correlated with disease activity in sJIA. High serum IL-18 exposure induces impaired MAPK and NFκB phosphorylation in NK cells.

Project description:BACKGROUND & AIMS:Production of interferon (IFN)-? by natural killer (NK) cells is attenuated during chronic infection with hepatitis C virus (HCV). We investigated whether this is due to intrinsic or extrinsic mechanisms of NK cells. METHODS:Peripheral blood mononuclear cells (PBMCs) were collected from patients with chronic HCV infection or uninfected blood donors (controls); NK cells and monocytes were isolated or eliminated. We cultured hepatoma cells that express luciferase-tagged subgenomic HCV replicons (Huh7/HCV replicon cells) or their HCV-negative counterparts (Huh7) with NK cells in the presence or absence of other populations of PBMCs. Antiviral activity, cytotoxicity, and cytokine production were assessed. RESULTS:NK cells produced greater amounts of IFN-? when PBMC were cocultured with Huh7/HCV replicon cells than with Huh7 cells; NK cells and PBMCs from controls suppressed HCV replication to a greater extent than those from patients with chronic HCV infection. This antiviral effect was predominantly mediated by tumor necrosis factor (TNF)-? and IFN-?. The antiviral activity of NK cells and their production of IFN-? were reduced when they were used in coculture alone (rather than with PBMC), or after depletion of CD14(+) monocytes, after knockdown of the inflammasome in monocytes, or after neutralization of interleukin-18, which is regulated by the inflammasome. These findings indicate a role for monocytes in NK cell activation. Compared with control monocytes, monocytes from patients with chronic HCV infection had reduced TNF-?-mediated (direct) and reduced NK cell-mediated (indirect) antiviral effects. Control monocytes increased the antiviral effects of NK cells from patients with chronic HCV infection and their production of IFN-?. CONCLUSIONS:Monocytes sense cells that contain replicating HCV and respond by producing interleukin-18 via the inflammasome and by activating NK cells. Patients with chronic HCV infection have reduced monocyte function, attenuating NK cell IFN-?-mediated responses.

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Adaptive Natural Killer Cells Integrate Interleukin-18 during Target-Cell Encounter.

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