Human CD56^bright NK cells: An update

Human NK cells can be subdivided into various subsets based on the relative expression of CD16 and CD56. In particular, CD56^brightCD16^-/dim NK cells are the focus of interest. They are considered efficient cytokine producers endowed with immunoregulatory properties, but they can also become cytotoxic upon appropriate activation. These cells were shown to play a role in different disease states, such as cancer, autoimmunity, neuroinflammation, and infection. Although their phenotype and functional properties are well known and have been extensively studied, their lineage relationship with other NK cell subsets is not fully defined, nor is their precise hematopoietic origin. In this article, we summarize recent studies about CD56^bright NK cells in health and disease and briefly discuss the current controversies surrounding them.