NK cell survival mediated through the regulatory synapse with human DCs requires IL-15Rα
Fabienne Brilot, Till Strowig, Susanne M. Roberts, Frida Arrey, Christian Münz
Fabienne Brilot, Till Strowig, Susanne M. Roberts, Frida Arrey, Christian Münz
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Research Article Immunology

NK cell survival mediated through the regulatory synapse with human DCs requires IL-15Rα

Abstract

DCs activate NK cells during innate immune responses to viral infections. However, the composition and kinetics of the immunological synapse mediating this interaction are largely unknown. Here, we report the rapid formation of an immunological synapse between human resting NK cells and mature DCs. Although inhibitory NK cell receptors were polarized to this synapse, where they are known to protect mature DCs from NK cell lysis, the NK cell also received activation signals that induced mobilization of intracellular calcium and CD69 upregulation. The high-affinity component of the receptor for IL-15, IL-15Rα, accumulated at the synapse center on NK cells, and blocking of IL-15Rα increased NK cell apoptosis and diminished NK cell survival during their interaction with DCs. Furthermore, IL-15Rα–deficient NK cells, obtained from donors with a history of infectious mononucleosis, showed diminished survival in culture with DCs. Synapse formation was required for IL-15Rα–mediated NK cell survival, because synapse disruption by adhesion molecule blocking decreased DC-induced NK cell survival. These results identify what we believe to be a novel regulatory NK cell synapse with hallmarks of spatially separated inhibitory and activating interactions at its center. We suggest that this synapse formation enables optimal NK cell activation by DCs during innate immune responses.

Authors

Fabienne Brilot, Till Strowig, Susanne M. Roberts, Frida Arrey, Christian Münz

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Figure 2

Cell-to-cell contact between NK cells and mDCs was established quickly and resulted in intracellular calcium release.

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Cell-to-cell contact between NK cells and mDCs was established quickly a...
(A and B) NK cells were conjugated by mixing them with mDCs for 1–5 min at 37°C. Cells were stained with anti–LFA-1 and anti-talin mAbs followed by Alexa Fluor 488–conjugated rabbit anti-mouse IgG (green). Shown are LFA-1 and talin in unconjugated resting NK cells (A) and in DC/NK cell conjugates (B) after 1 min of interaction. White arrows denote DC/NK cell interface. Representative images from 3 experiments are shown. Scale bars: 5 μm. (C) Mobilization of intracellular calcium was monitored by flow cytometry. Basal [Ca2+] was recorded during 30 s, after which indo-1–loaded NK cells and mDCs were mixed with each other for 1 min at 37°C and changes in the fluorescence of NK cells were monitored. NK cells were gated on size, CD3–, and CD56bright. Black arrows indicate when flow acquisition was appended after formation of conjugates and incubation of cells at 37°C. Data show the mean value of the response and are representative of 3 experiments.