NK cell activating receptors and tumor recognition in humans

Natural killer (NK) cells have been known for many years as the lymphocyte subset characterized by the highest cytolytic potential against virus-infected and tumor-transformed cells. A surprisingly high number of surface molecules have been recognized that regulate human NK cell function. These include MHC-specific inhibitory receptors, which impair NK cells' ability to attack normal self-tissues, and activating receptors and coreceptors that allow them to recognize and kill transformed cells. The recent identification of some of the cellular ligands specifically recognized by these receptors/coreceptors contributes to elucidation of the mystery of the role played by NK cells in immune responses.