In vivooverexpression of Flt3 ligand expands and activates murine spleen natural killer dendritic cells

Abstract

Natural killer dendritic cells (NKDC) are a unique class of murine immune cells that possess the characteristics of both natural killer (NK) cells and dendritic cells (DC). Because NKDC are able to secrete IFN-gamma, directly lyse tumor cells, and present antigen to naïve T cells, they have immunotherapeutic potential. The relative paucity of NKDC, however, impedes their detailed study. We have found that in vivo, overexpression of the hematopoietic cytokine Flt3 ligand (Flt3L) expands NKDC in various organs from 2-18 fold. Flt3L expanded splenic NKDC retain the ability to lyse tumor cells and become considerably more potent at activating naïve allogeneic and antigen-specific T cells. Compared to normal splenic NKDC, Flt3L-expanded splenic NKDC have a more mature phenotype, a slightly increased ability to capture and process antigen, and a similar cytokine profile. In vivo, we found that Flt3L-expanded splenic NKDC are more effective than normal splenic NKDC in stimulating antigen-specific CD8 T cells. Additionally, we show that NKDC are able to cross-present antigen in vivo. The ability to expand NKDC in vivo using Flt3L will facilitate further analysis of their unique biology. Moreover, Flt3L-expanded NKDC may have enhanced immunotherapeutic potential, given their increased ability to stimulate T cells.

Coexpression of Flt3 ligand and GM-CSF genes modulates immune responses induced by HER2/neu DNA vaccine

“…Furthermore, our results also demonstrate that splenocytes from mice vaccinated with pN-neu plus pFLAG or pFL/ pGM had more potent cytolytic function, which included NK-cell activity. Because Flt3L can expand and activate murine splenic NKDC, a unique subset of cells possessing the characteristics of both NK and DC, and Flt3L-expanded NKDC have potent cytolytic function and increased T-cell stimulatory capacity, 41 we cannot exclude the possibility that NKDC or other effector cells may participate in the antitumor immune responses. To this end, DC engineered to express Flt3L were demonstrated to enhance tumor-specific cytotoxic T-and NK-cell responses and induce antitumor immunity.…”

The ‘kiss of death’ by dendritic cells to cancer cells

“…More interestingly, the authors showed that, subsequent to OVA-loaded YAC-1 cell killing, NKDCs up-took and presented OVA antigen to specific class-I restricted T cells, thus claiming the benefit of these cells to kill their target and directly cross-present resultant antigen to specific T cells. 53 However, several major pitfalls resided in the recognition of NKDCs as a cell type per se, with a dual functional identity directly linking innate and adaptive immunity. First, the isolation of this subset is based on CD11c and NK1.1 expression, which does not allow a clear distinction from classical NK cells (for extensive comments see Spits and Lanier 61 ).…”

Killer dendritic cells: mechanisms of action and therapeutic implications for cancer

“…Flt-3 ligand and GM-CSF have been used to expand systemic DC populations in both humans and mice. However, in mice, IKDC are preferentially expanded in vivo by CpG, 15,17 Flt-3 ligand 50 (or during viral infection 14 ). In the event that a human equivalent of murine NKDC/IKDC is identified, factors supporting their expansion and sustained functionality in vivo should receive considerable clinical attention.…”