Replicative Response, Immunophenotype, and Functional Activity of Monocyte-Derived versus CD34+-Derived Dendritic Cells Following Exposure to Various Expansion and Maturational Stimuli

Dendritic cells (DCs), generated ex vivo from blood mononuclear cells (PBMC) or CD34+ stem cells, are being used to develop novel immunotherapies. To establish optimal DC generation, a direct comparison of the optimal cell source, culture conditions, and maturation stimuli was performed, utilizing phenotypic and functional assays as end points. Plastic adherent monocytes from PBMC were expanded in a serum-free medium (X-Vivo 10) for 7 days using GM-CSF/IL-4; CD34+ cells were expanded for 14 days using GM-CSF/IL-4/ Flt3L, in either X-Vivo 10 alone or with albumin or autologous plasma. Expanded DC from both cell sources were matured for 7 days with CD40L or IFN-α/TNF-α. Starting from 2 × 107 monocytes, the optimal expansion/maturation process yielded 1.73 ± 0.52 × 106 CD86+ DC. Optimal expansion of CD34+ cells (83.9 ± 25.0-fold) was achieved using X-Vivo 10 with 5% plasma, matured with CD40L, and yielded 10.68 ± 2.72 × 106 CD86+ DC from 1 × 106 CD34+ cells. Mature DC from PBMC or CD34+ cells had similar enhanced expression of MHC class II HLA-DR, CD80, CD83, and CD86 and were potent stimulators of mixed lymphocyte reactions. Prior to maturation, all groups of DC actively phagocytosed apoptotic melanoma cells (approximately 50% of HLA-DR+). CD34+ DC matured with CD40L or IFN-α/TNF-α had reduced phagocytic capability (34 and 31% of HLA-DR+ DC, respectively). Similar expansion and functional activity was found using cryopreserved DC precursors, cultured in gas permeable bags. We conclude that both cell lineages produce potent mature DC, permitting exploration of the optimal clinical strategy to trigger anti-tumor immune responses in patients with malignancies.