AB46. DC factory: a new source of DC derived from CD34+ progenitor cells
Gang Liu1,2, Kang Li1,2, Jiantao Dong1,2, Jianhui Cai1,2
Background: Dendritic cell (DC) serves as “police” to recognize abnormal antigen and elicit potent adaptive immune responses by activating naïve T lymphocytes, and it is a promising immune tool in from of DC-based vaccine which is effective in building anti-tumor immune barrier. Large amount of matured, functional, homogeneous DC are essential for DC vaccination or DC-induced immunotherapy, but number of autologous DC from cancer patients ranged from 106-108 that is insufficient for clinical use. Thus, exploration of new method of DC generation is urgently needed.
Objective: To explore a new method of DC generation from CD34+ progenitors in fresh cord blood and identify the novel CD34-DC vaccine has comparable or superior capacity in inducing immune responses ex vivo compared with conventional PBMC-DC vaccine.
Methods: Isolation of CD34+ progenitors of cord blood and cultured them in GM-CSF/SCF medium for cell expansion for continuously 30 days, and DC were harvested by plastic adherent every 3 days during the whole expansion period. DC derived from peripheral blood monocytes were served as controls. Both of them were compared in morphology, phenotype, and functional assays including antigen uptake, mixed leukocyte reaction, cytokine secretion and chemotaxis. And in addition, DC vaccines were prepared with tumor lysate loading and the IFN-γ, cytotoxicity of CTL was compared.
Results: (I) GM-CSF/SCF cytokines lead to -10 log expansion of total CD34+ cells and -9 log of DCs during continuous 30 days cultivation ex vivo. CD34-DC exhibited similar features of morphology with PBMC-DC; (II) the expression rate of CD80, CD83, CD86 and HLA-DR in CD34-DC were comparable to PBMC-DC when matured, and in addition, CD80 expression in CD34-DC upregulated earlier; (III) CD34-DC exhibited stronger phagocytosis than PBMC-DC and the fifth culturing day in GM-CSF/IL-4 medium represented an ideal time points for antigen loading, even for those thawed from cryopreserved DCs in liquid nitrogen; (IV) CD34-DC vaccine secreted higher levels of IL-12 and IL-10 when stimulated by cocktailed cytokines than PBMC-DC, and the antigen-specific cytotoxic lymphocytes (CTLs) induced by them produced much more IFN-γ; (V) CD34-DC vaccine induced CTLs exhibited stronger cytotoxicity than those induced by PBMC-DC; (VI) CD34+ progenitors in cord blood had stable amplification capability and differentiation potential to dendritic cells.
Conclusions: Hence, a “DC factory” based on CD34+ progenitor enriched cord blood might be established, and its final production—DC vaccine, might be a promising immune stimulator for further use in cancer immunotherapy.
