IMMUNOBIOLOGY Dynamic behavior of NK cells during activation in lymph nodes

nists induce natural killer (NK)–cell activa-tion by stimulating dendritic cells (DCs) to produce cytokines and transpresent IL-15 to NK cells. Yet the cellular dynam-ics underlying NK-cell activation by DCs in secondary lymphoid organs are largely unknown. Here, we have visualized NK-cell activation using mice in which NK cells and DCs express different fluores-cent proteins. In response to polyI:C or lipopolysaccharide, NK cells maintained a vigorous migratory behavior, establish-ing multiple short contacts with maturing DCs. Furthermore, mature antigen-loaded DCs that made long-lived interactions with T cells formed short-lived contacts with NK cells. The different behaviors of T cells and NK cells during activation was corre-lated with distinct calcium responses upon interaction with DCs. That NK cells become activated while remaining motile may constitute an efficient strategy for sampling local concentrations of cyto-kines around DCs in secondary lymphoid tissues. (Blood. 2009;114:3227-3234