The role of natural killer cells in tumor control--effectors and regulators of adaptive immunity.

Natural killer (NK) cells are the primary effector cells of the innate immune system and have a well-established role in tumor rejection in a variety of spontaneous and induced cancer models. NK cell function is regulated by a complex balance of inhibitory and activating signals that allow them to selectively target and kill cells that display an abnormal pattern of cell surface molecules, while leaving normal healthy cells unharmed. In this review we discuss NK cell function, the role of NK cells in cancer therapies, the emerging concept of bi-directional cross-talk between NK cells and dendritic cells, and the implications of these interactions for tumor immunotherapy.