Abstract
The use of impedance-based label free cell analysis is increasingly popular and has many different applications. Here, we report that a real-time cell analyzer (RTCA) can be used to study the stimulation of Natural Killer (NK) cells. Engagement of NK cells via plate-bound antibodies directed against different activating surface receptors could be measured in real time using the label-free detection of impedance. The change in impedance was dependent on early signal transduction events in the NK cells as it was blocked by inhibitors of Src-family kinases and by inhibiting actin polymerization. While CD16 was the only receptor that could induce a strong change in impedance in primary NK cells, several activating receptors induced changes in impedance in expanded NK cells. Using PBMCs we could detect T cell receptor-mediated T cell activation and CD16-mediated NK cell activation in the same sample. Performing a dose-response analysis for the Src-family kinases inhibitor PP1 we show that T cells are more sensitive to inhibition compared to NK cells. Our data demonstrate that the RTCA can be used to detect physiological activation events in NK cells in a label-free and real-time fashion.
Highlights
Natural killer (NK) cells are an essential part of the innate immune system
Culturing Natural Killer (NK) cells on non-coated E-plates or on E-plates, which were coated with goat-antimouse antibodies, did not result in any significant changes of cell index (CI) values compared to empty wells with medium alone (Fig. 1A)
Pretreatment of NK cells with PP1 reduced the CI in anti-CD16 coated wells to background levels (Fig. 1A,B), confirming that the change in CI is caused by specific NK cell activation events
Summary
Natural killer (NK) cells are an essential part of the innate immune system. They belong to a group of cytotoxic innate lymphoid cells and are important for early and effective immune responses against cancer and virus-infected cells[1,2,3]. We could recently show that in contrast to T cells, ITAM-based receptors in NK cells rely less on the activity of Src-family kinases to initiate their signaling networks[20]. Impedance based-assays such as the xCELLigence system have the advantages of providing label-free, real-time measurements of cellular functions This method has been applied to successfully measure proliferation, migration, cytotoxicity and receptor-mediated signaling[24,25,26]. It records changes in cell morphology, adherence and cell numbers as changes in impedance over time using specialized E-plates with gold-electrodes at the bottom of the well[27,28]. We use an impedance-based assay system to measure NK cell responses upon the engagement of various surface receptors
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