THE INFLUENCE OF INTERLEUKIN (IL)-4, IL-13, AND FLT3 LIGAND ON HUMAN DENDRITIC CELL DIFFERENTIATION FROM CORD BLOOD CD34+ PROGENITOR CELLS

: Culturing cord blood CD34+ cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor (TNF)-alpha for 12 days, and stem cell factor (SCF) for 5 days, resulted in a 40- +/- 26-fold expansion in cell numbers, with 38 +/- 20% dendritic cells (DCs). Interleukin (IL)-4 and IL-13, which share properties, were examined first. Adding either one to the former baseline condition beginning on day 0 halved cell growth while the percentage of DCs increased to 60-70%, resulting in unchanged DC yields. Delaying use of IL-4 or IL-13 to day 5 led to 25-fold cell expansion with approximately 80% DC, the yield of which was then twofold over that of baseline control cultures, while numbers of other cells decreased. IL-4 and IL-13 had no additive or antagonistic effect on DC generation. The effect of Flt3 ligand (FL), known to enhance proliferation of hematopoietic progenitors induced by other growth factors, was examined next. FL added alone induced DC in the same manner as SCF. Using both FL and SCF throughout the culture period enhanced total cell recovery fourfold above that of baseline control cultures on day 12 compared with > or =2.5-fold if either one was stopped on day 5. When both FL and SCF were used for 12 days, DC recovery was fivefold that of control cultures, whereas it was to three- to 3.5-fold when either one was stopped on day 5. A similar trend was noted for CD15+ cells, and, to a lesser extent, for CD14+ cells. Finally, using SCF and FL for 12 days, with IL-4 or IL-13 added from day 5 onwards, led to comparably enhanced cell yields relative to control cultures with approximately 60% DC. These data underline the need to use appropriate cytokine combinations and schedules to optimize generation of DCs from CD34+ progenitors. Associated with GM-CSF and TNF-alpha, IL-4 or IL-13 promotes differentiation and maturation of DCs over other myeloid cells. Under the same baseline conditions, FL appears to potentiate SCF throughout the culture period, inducing proliferation and development of DC as well as of other myeloid cells.