Abstract: Natural killer cells (NK) are important innate immune cells that do not require prior antigen exposure and can directly recognize and attack virus-infected cells and tumor cells. The activation and effector functions of NK cells are regulated by a balance of signals delivered through their surface activating receptors and inhibitory receptors, which bind to ligands on target cells to achieve cytotoxicity via “induced self” and “missing self” recognition models. The killing mechanisms of NK cells primarily include release of cytotoxic granules such as perforin and granzymes to induce target cell lysis, death receptor-mediated apoptosis, secretion of various cytokines,chemokines and growth factors to coordinate with other immune cells in killing tumor cells, thereby generating secondary immune responses and antibody-dependent cellular cytotoxicity(ADCC).

Key words: natural killer cells, chimeric antigen receptor-NK cells (CAR-NK cells), tumor, immunotherapy, carrier delivery