Natural killer cell-based immunotherapeutic strategies.

Not until recently have Natural killer (NK) cells stepped out of the shadow of T-cells to be considered for cellular therapy of malignant diseases. This evolution has been facilitated by the discovery of specific receptors on NK cells that interact with HLA molecules on target cells but also the discovery of specific activating receptors. Since NK cells represent only about 10% of the lymphocyte population in blood, separation and enrichment are important steps if NK cells are to be used clinically. This is of particular consideration in the setting of allogeneic NK cell infusion where contaminating T-cells could potentially induce graft versus host disease. This review will describe the requirements for NK cells to recognize target cells, their ex vivo expansion and potential therapeutic applications.