Selective Generation of Different Dendritic Cell Precursors from CD34 super(+) Cells by Interleukin-6 and Interleukin-3

There is a growing interest in generating dendritic cells (DCs) for using as vaccines. Several cytokines, especially stem cell factor (SCF) and FLT3-ligand (FL), have been identified as essential to produce large numbers of myeloid precursors and even to increase DC yield obtained by the action of granulocyte- macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor alpha (TNF- alpha ). However, there are few studies on the effect of the early-acting cytokines, commonly used to expand CD34 super(+) progenitor cells, on DC generation. We report here that in the absence of serum, SCF, FL, and thrombopoietin (TPO) plus interleukin-6 (IL-6) and SCF, FL, and TPO plus IL-3 were able to generate CD14 super(+)CD1a super(-) and CD14 super(-) CD1a super(+) myeloid DC precursors from CD34 super(+) cells, but IL-6 had an inhibitory effect on the generation of CD14 super(-) CD1a super(+) cells. Both DC precursors differentiated into mature DCs by GM-CSF, IL-4, and TNF- alpha , and DCs obtained from both types of culture exhibited equal allostimulatory capacity. CD1a super(+) DCs generated could be identified on the basis of DC-specific intracellular adhesion molecule-grabbing nonintegrin (DC- SIGN) expression, a novel C-type lectin receptor expressed on dermal DCs but not on Langerhans cells. In addition, the inclusion of IL-3 to the culture medium induced the appearance of CD13 super(-) cells that differentiated into plasmacytoid DC (DC2) on the addition of TNF- alpha , allowing the identification of developmental stages of DC2. Like true plasmacytoid DCs, these cells secreted interferon- alpha after TLR9-specific stimulation with a specific CpG nucleotide.