Natural killer (NK) cells are innate lymphoid cells that, together with CD8+ T lymphocytes, are tightly correlated with immunesurveillance and the elimination of transforming and malignant cells both during early steps of tumorigenesis and metastasis. This capacity is due, but not limited to, their great cytotoxic capacity upon recognition of stress-related activating ligands of NK cells on the surface of tumor cells. Due to the emerging role of NK cells in the response to treatment with immune checkpoint blockers (ICBs) and other immunotherapies, it has become essential to deeply study this immune subset. As mentioned above, NK cell antitumor responses not only rely on their high cytotoxic capacity, cytokine production by this immune subset, such as interferon gamma (IFN-γ) or tumor necrosis factor (TNF-α), also plays a key role on NK cell function. In this chapter, we provide a detailed protocol to measure the intracellular expression of cytokines produced by NK cells upon stimulation. A step-by-step guide to isolate peripheral blood mononuclear cells, purify NK cells from whole blood, co-culture with tumor cell lines and evaluate their cytokine production capacity by flow cytometry is here provided.
Keywords: Cytokine; Flow cytometry; IFNG; NK cells; Tumor immunology.
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