Recruitment and activation of natural killer cells in vitro by a human dendritic cell vaccine.

Recruitment of circulating natural killer (NK) cells into inflamed lymph nodes is known to provide a potent, IFN-gamma-dependent boost for Th1-polarized immune responses in mouse models. Such NK cell recruitment into draining lymph nodes is induced by certain s.c. injected adjuvants, including mature vaccine dendritic cells (DC), and is mediated by a CXCR3-dependent pathway. Here, we show that monocyte-derived immature human DCs stimulated with polyinosinic acid:polycytidylic acid, IFN-alpha, tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and IFN-gamma, alpha-type 1-polarized DC (alpha DC1), secrete profuse amounts of the CXCR3 ligand CXCL9/MIG and substantial amounts of CXCL10/IP-10 and CXCL11/I-TAC after withdrawal of maturation stimuli. In sharp contrast, no measurable production of these chemokines was found in DCs after maturation with the current gold standard maturation cocktail for human DC-based cancer vaccines consisting of TNF-alpha, IL-1 beta, IL-6, and prostaglandin-E(2) (PGE(2)-DC). PGE(2)-DCs preferentially produced the Th2 and regulatory T-cell-attracting chemokines CCL17/TARC and CCL22/MDC, whereas only marginal levels of these chemokines were produced by alpha DC1s. Functional studies in vitro showed that supernatants from mature alpha DC1s actively recruited CD3(-)CD56(+) NK cells and that adding anti-CXCL9/MIG antibodies to the alpha DC1 supernatant substantially reduced this recruitment. Finally, alpha DC1s were able to induce IFN-gamma production when cocultured with resting autologous NK cells, but only if concurrent CD40 ligation was provided. These novel findings indicate that injected human alpha DC1-based vaccines have the potential to recruit and activate NK cells during their arrival to draining lymph nodes and that this feature may be of relevance for efficient priming of Th1 cells and CTLs.