Human dendritic cell differentiation pathway from CD34+ hematopoietic precursor cells

Abstract

The most effective antigen-presenting cells for T lymphocytes are dendritic cells (DCs), the differentiation pathway of which, however, is incompletely characterized. We examined here how DCs differentiated from human cord blood CD34+ progenitor cells cultured with granulocyte-macrophage colony-stimulating factor, tumor necrosis factor-α, and stem cell factor. After 5 days, 2 of 3 nonadherent cells were CD13(hi)HLA-DR(hi)CD4+, half of them were also CD14+, and ≤10% were CD1a+. When day-5 sorted CD13(hi)CD1a- and CD13(lo) cells were further cultured, CD1a+ cells appeared in the already CD13(hi) population, whereas CD13(hi) cells, a minority of which rapidly became CD1a+, emerged from the CD13(lo) population. By day 12, still 66% of bulk cells in suspension were CD13(hi), most of which displayed high forward and side scatters of large granular cells. Half of CD13(hi) cells were CD1a+. All CD13(hi) cells expressed to the same extent DR, CD4, costimulatory and adhesion molecules, and various amounts of CD14. CD1a+ cells stimulated allogeneic lymphocytes more than CD13(hi)CD1a- cells and, although they were CD14+, both cell types were nonspecific esterase-negative nonphagocytic cells and were stronger mixed leukocyte reaction stimulators than were their macrophage counterparts. Eventually, the percentage of CD1a+ cells decreased. However, typical CD1a+ DCs still emerged in culture of sorted day-12 CD13(hi)CD1a- cells, and adding interleukin-4 to bulk cultures at that time led to the persistence of the CD1a+ population while diminishing CD14 expression. Thus, this system results first in the differentiation of CD13(hi) precursors that strongly express DR and CD4, from which more mature CD1a+ DCs continuously differentiate all along the culture period.