Hanging in the balance: natural killer cell recognition of target cells Review Article

Natural killer (NK) cells kill certain tumor cells and virus-infected cells directly. Until recently, little was known about how they recognize their targets. Now, several candidate NK receptors have been identified, some of which may have carbohydrate ligands. Some of the receptors deliver positive signals, others negative signals. Thus NK cells seem to balance many different inputs to decide whether to kill a target.