Recombinant adenovirus-engineered dendritic cells (Ad.DC) are potent vaccines for induction of anti-viral and anti-cancer T cell immunity. The effectiveness of Ad.DC vaccines may depend on the newly described ability of Ad.DC to crosstalk with natural killer (NK) cells via cell-to-cell contact, and to mediate activation, polarization and bridging of innate and adaptive immunity. For this interaction to occur in vivo, Ad.DC must be able to attract NK cells from surrounding tissues or peripheral blood. We developed a novel live mouse imaging system-based NK-cell migration test, and demonstrated for the first time that human Ad.DC induced directional migration of human NK cells across subcutaneous tissues, indicating that Ad.DC-NK cell contact and interaction could occur in vivo. We examined the mechanism of Ad.DC-induced migration of NK cells in vitro and in vivo. Ad.DC produced multiple chemokines previously reported to recruit NK cells, including immunoregulatory CXCL10/IP-10 and proinflammatory CXCL8/IL-8. In vitro chemotaxis experiments utilizing neutralizing antibodies and recombinant human chemokines showed that CXCL10/IP-10 and CXCL8/IL-8 were critical for Ad.DC-mediated recruitment of CD56(hi)CD16(-) and CD56(lo)CD16(+) NK cells, respectively. The importance of CXCL8/IL-8 was further demonstrated in vivo. Pretreatment of mice with the neutralizing anti-CXCL8/IL-8 antibody led to significant inhibition of Ad.DC-induced migration of NK cells in vivo. These data show that Ad.DC can recruit spatially distant NK cells toward a vaccine site via specific chemokines. Therefore, an Ad.DC vaccine can likely induce interaction with endogenous NK cells via transmembrane mediators, and consequently mediate Th1 polarization and amplification of immune functions in vivo.