Enhancement of Human Cord Blood CD34+ Cell-Derived NK Cell Cytotoxicity by Dendritic Cells

Abstract

NK cells and dendritic cells (DCs) are both important in the innate host defense. However, the role of DCs in NK cell-mediated cytotoxicity is unclear. In this study, we designed two culture systems in which human cord blood CD34+ cells from the same donor were induced to generate NK cells and DCs, respectively. Coculture of the NK cells with DCs resulted in significant enhancement of NK cell cytotoxicity and IFN-γ production. However, NK cell cytotoxicity and IFN-γ production were not increased when NK cells and DCs were grown together separated by a transwell membrane. Functional studies demonstrated that 1) concanamycin A, a selective inhibitor of perforin/granzyme B-based cytolysis, blocked DC-stimulated NK cytotoxicity against K562 cells; and 2) neutralizing mAb against Fas ligand (FasL) significantly reduced DC-stimulated NK cytotoxicity against Fas-positive Jurkat cells. In addition, a marked increase of FasL mRNA and FasL protein expression was observed in DC-stimulated NK cells. The addition of neutralizing mAb against IL-18 and IL-12 significantly suppressed DC-stimulated NK cell cytotoxicity. Neutralizing IFN-γ Ab almost completely inhibited NK cell cytotoxicity against Jurkat cells. These observations suggest that DCs enhance NK cell cytotoxicity by up-regulating both perforin/granzyme B- and FasL/Fas-based pathways. Direct interaction between DCs and NK cells is necessary for DC-mediated enhancement of NK cell cytotoxicity. Furthermore, DC-derived IL-18 and IL-12 were involved in the up-regulation of NK cell cytotoxicity, and endogenous IFN-γ production plays an important role in Fas-mediated cytotoxicity.

Intratumoral injection of immature dendritic cells enhances antitumor effect of hyperthermia using magnetic nanoparticles

“…In addition, DCs have been reported to activate NK cells by secretion of cytokines (IL-12 and IL-18) and costimulatory molecules. 45,46 Because NK cells can kill cancer cells that show low MHC class I expression, the activation of not only CTLs but also NK cells is helpful in melanoma therapy. These cytotoxic cells are stimulated in the lymph nodes by antigen presentation and/or cytokine secretion of mature DCs that migrate after hyperthermia.…”

Upregulation of natural killer cells functions underlies the efficacy of intratumorally injected dendritic cells engineered to produce interleukin-12

“…DC-NK cross-talk through cytokines has been recently confirmed with human DC and NK cells derived in vitro from cord blood CD34 ϩ cells [34]. In this case an involvement of IL-12, IL-18, and possibly IFN-␥ produced by DC was unraveled, showing also a possible role of DC-expressed CD40 acting through an unknown counterreceptor on NK cells distinct from CD40L [34]. In both pieces of work, DC were matured with TNF-␣ prior to exposure to NK cells.…”

“…It is worth mentioning in this regard that functionally inducible membrane-associated IL-12 on DC has been reported [50]. DC-NK cross-talk through cytokines has been recently confirmed with human DC and NK cells derived in vitro from cord blood CD34 ϩ cells [34]. In this case an involvement of IL-12, IL-18, and possibly IFN-␥ produced by DC was unraveled, showing also a possible role of DC-expressed CD40 acting through an unknown counterreceptor on NK cells distinct from CD40L [34].…”

“…The upregulation of NK functions that has already been seen in vitro with mature DC requires direct DC-NK contact [33] with the involvement of IL-12 and IL-18 [34]. We show that immature DC, such as those used for intratumoral injection [5,6], do not upregulate NK functions unless transfected with IL-12 and that cultured DC engineered to produce IL-12 potently activated NK cells both in vivo and in vitro.…”

Cimetidine modulates the antigen presenting capacity of dendritic cells from colorectal cancer patients

“…With the recent development of culture methods for propagating DC on a large scale from human peripheral blood mononuclear cells (PBMC) (Caux et al, 1992;Sallusto and Lanzavecchia, 1994), vaccination aimed at efficient production of CTL with tumour-antigenloaded DC represents a potentially powerful strategy to induce tumour rejection (Young and Inaba, 1996;Nestle et al, 1998). Moreover, since it has also been reported that DC stimulate NK cell activity (Fernandez et al, 1999;Yu et al, 2001), DC should be considered to be associated intimately with not only the production of CTL but also with the whole process of antitumour cellmediated immunity. However, there is little published information regarding the influence of cimetidine on DC function.…”