For this purpose, we isolated human NK cells from the blood of healthy donors, cocultured them with human melanoma cells overexpressing NGFR, and measured NK cell activation by analyzing the degranulation marker CD107a and the intracellular synthesis of the cytokines tumor necrosis factor–α (TNFα) and interferon-γ (IFNγ) by flow cytometry (Fig. 2E). Here, NGFR is linked to melanoma.