Distinguishing features of developing natural killer cells.

Although NK cells were initially described as lymphocytes that lacked the characteristic markers of B and T cells, we now appreciate the plethora of activating and inhibitory receptors that define the NK cell surface phenotype. Recent studies have provided new insights into the molecular mechanisms that drive NK cell development, control the NK cell receptor repertoire and the cytokines that define the NK cell niche. These findings form the basis for an updated model of NK cell differentiation.