Figure 4: Cytotoxic assay by FACS analysis. A: Schematic view of the cytotoxic assay which allows analysing simultaneously target cells and cytotoxic T or NK cells. B: Prototypical example of cytotoxic assay by FACS with NK cells. NK cells are gated and excluded from the analysis (upper panel), the double positive CFSE+/7- AAD+ NPC population represents NPC lysed by the NK cells. When the NK cells are gated on the living cells (lower panel), the expression of CD107a and the secretion of IFN-γ can be analysed.