Functional differences between dendritic cells derived from CD34+ bone marrow and peripheral blood stem cells

It has been previously demonstrated that dendritic cells (DCs) are characterized by an immature stage with high antigen internalization capacity, followed by a mature stage with predominantly immunostimulatory ability. The shift from the immature to the mature state can be induced in vitro by the addition of tumor necrosis factor-a (TNFa). The aim of our study was to investigate the maturation steps of DCs obtained from CD34(+) cells from peripheral blood stem cells (PBSC) and bone marrow (BM).

DCs were generated in vitro from PBSC and BM CD34(+) selected cells. The endocytic activity of the cells was measured by means of dextran-FITC uptake and alloreactivity evaluated with mixed leukocyte reactions. Immunophenotypic analysis was performed by flow cytometry.

We observed that DCs from PBSC, in contrast to the BM derived DCs, were never able to take up soluble antigens. Mixed leukocyte reactions (MLR) performed both on PBSC and BM CD34(+) derived DCs showed an allo-stimulatory activity comparable to normal controls at day 10, but significantly higher at day 14 after the addition of TNFa. Immunophenotypic analysis showed typical dendritic markers in all the samples and, after treatment with TNFa, enhanced expression of co-stimulatory molecules.

Our data seem to indicate that, in our culture conditions, BM-derived DCs could be efficiently used for pulsing with specific peptides, while PBSC-derived DCs, being functionally mature, should be more suitable for gene therapy.