IL-4 AND CD40 LIGATION AFFECT DIFFERENTLY THE DIFFERENTIATION, MATURATION, AND FUNCTION OF HUMAN CD34(-DERIVED CD1A(+)CD14(-) AND CD1A(-)CD14(+) DENDRITIC CELL PRECURSORS IN-VITRO() CELL)

We examined the effect of interleukin (IL)-4 or CD40 ligation on the d ifferentiation and maturation of CD1a(+)CD14(-) and CD1a(-)CD14(+) den dritic cell (DC) precursors. Cord blood CD34(+) cells were cultured wi th granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor alpha, to which stem cell factor and Flt-3 ligand wer e added for 5 days. Phenotypic analysis of DC precursors on culture da y 7 showed that CD1a(+)CD14(-) cells expressed higher CD11c and CD80 l evels and lower CD116/GM-CSFR and CCR-5 levels than their CD1a(-)CD14( +) counterparts. Culturing CD1a(+)CD14(-) precursors with GM-CSF and T NF-alpha resulted in DC with heterogeneous CD1a, HLA;SMDR (DR), CD11b, and CD83 expression, 10% of which acquired CD14. IL-4 and CD40 ligati on affected their differentiation in contrasting ways: IL-4 induced CD 1a(hi)CD14(-) DR(lo)D11b(+)CD83(-)S100(+) DC with reduced MLR-stimulat ing capacity, whereas CD40 ligation led to o)/(-)CD14(-)CD40(-)DR(hi)C D11b(-)CD83(+)S100(+/-) DC with stronger MLR-stimulating capacity. Als o, both IL-4 and CD40 ligation promoted RelB expression and nuclear tr anslocation. When CD1a(-)CD14(+) precursors were maintained in only th e presence of GM-CSF and TNF-alpha, this led to mixed populations of a dherent macrophages and nonadherent CD1a(-)CD14(+) monocytes, and of C D1a(+)CD14(-) and CD1a(+)CD14(-) DC, which were DR(lo)CD11b(+)-CD83(-) S100(-). IL-4 or CD40 ligation prevented their differentiation into ma crophages and resulted in DC with phenotypes close to those issued fro m 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(-) prec ursors. Thus, IL-4 or CD40 ligation induced CD1a(+)Cd14(-) and CD1a(-) CD14(+) DC precursors to differentiate into phenotypically close but f unctionally different DC populations, suggesting that DC function is p rimarily determined by their origin. The heterogeneity of DC should th en be related to different developmental pathways and to different sta ges of maturation/activation.