IL15 and neoplasm: Notably, cytokine-expressing NK cells, including CD19IL15 CAR-NKs (Figure 4c), IL-15 NKs (Figure 4d), and IL-21 NKs (Figure 4e) exhibited a small peak in cytotoxic NK cell ratios, corresponding to the transition of a subset of cytotoxic NK cells into the vigilant phenotype upon tumor clearance.