Plasmacytoid dendritic cell-induced migration and activation of NK cells in vivo.

NK cells are cytotoxic cells of the innate immune system. They have been found to be critical in the defense against infections and also against some tumors. Recent studies have shown that NK cells require signals from accessory cells to induce their recruitment and activation at the site of infection or tumor growth. In this study, we examined whether plasmacytoid DC (pDC) could recruit and activate NK cells in vivo. When CpG-stimulated pDC were injected i.p. to C57BL/6 mice, they efficiently recruited NK cells, a process that was dependent on NK cell CXCR3 and CD62L and in part on CCR5. NK cells isolated from the peritoneum of mice inoculated with TLR7/8 or TLR9-stimulated pDC exhibited greater cytotoxicity against YAC-1 tumor cells than NK cells recovered from mice inoculated with control pDC. The present results are discussed in relation to pDC-induced NK cell migration and activation in vivo.