IL-4 and CD40 ligation affect differently the differentiation, maturation, and function of human CD34+ cell-derived CD1a+CD14- and CD1a-CD14+ dendritic cell precursors in vitro

We examined the effect of interleukin (IL)-4 or CD40 ligation on the differentiation and maturation of CD1a(+)CD14(-) and CD1a(-)CD14(+) dendritic cell (DC) precursors. Cord blood CD34(+) cells were cultured with granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor alpha, to which stem cell factor and Flt-3 ligand were added for 5 days. Phenotypic analysis of DC precursors on culture day 7 showed that CD1a(+)CD14(-) cells expressed higher CD11c and CD80 levels and lower CD116/GM-CSFR and CCR-5 levels than their CD1a(-)CD14(+) counterparts. Culturing CD1a(+)CD14(-) precursors with GM-CSF and TNF-alpha resulted in DC with heterogeneous CD1a, HLA;SMDR (DR), CD11b, and CD83 expression, 10% of which acquired CD14. IL-4 and CD40 ligation affected their differentiation in contrasting ways: IL-4 induced CD1a(hi)CD14(-) DR(lo)D11b(+)CD83(-)S100(+) DC with reduced MLR-stimulating capacity, whereas CD40 ligation led to CD1a(lo)/(-)CD14(-)CD40(-)DR(hi)CD11b(-)CD83(+)S100(+/-) DC with stronger MLR-stimulating capacity. Also, both IL-4 and CD40 ligation promoted RelB expression and nuclear translocation. When CD1a(-)CD14(+) precursors were maintained in only the presence of GM-CSF and TNF-alpha, this led to mixed populations of adherent macrophages and nonadherent CD1a(-)CD14(+) monocytes, and of CD1a(+)CD14(-) and CD1a(+)CD14(-) DC, which were DR(lo)CD11b(+)-CD83(-)S100(-). IL-4 or CD40 ligation prevented their differentiation into macrophages and resulted in DC with phenotypes close to those issued from CD1a(+)CD14(-) precursors, with only a minority staying CD14(+) but most being S100(-); their MLR-stimulating capacity also increased but remained lower than that of DC differentiated from CD1a(+)CD14(-) precursors. Thus, IL-4 or CD40 ligation induced CD1a(+)Cd14(-) and CD1a(-)CD14(+) DC precursors to differentiate into phenotypically close but functionally different DC populations, suggesting that DC function is primarily determined by their origin. The heterogeneity of DC should then be related to different developmental pathways and to different stages of maturation/activation.