EXPANSION OF IMMUNOSTIMULATORY DENDRITIC CELLS AMONG THE MYELOID PROGENY OF HUMAN CD34(-MARROW PRECURSORS CULTURED WITH C-KIT LIGAND, GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR, AND TNF-ALPHA() BONE)

Human CD34(+) bone marrow progenitors cultured in the presence of gran ulocyte-macrophage CSF (CM-CSF) develop along a myeloid pathway, and t he addition of exogenous TNF-alpha leads to the differentiation of den dritic cells among the myeloid progeny These bone marrow CD34(+)-deriv ed dendritic cells that develop during 2-wk culture have the same morp hologic, phenotypic, and functional properties that distinguish mature dendritic cells in blood. c-kit ligand does not directly influence de ndritic cell differentiation per se, but rather increases the total ce ll number in synergistic combination with GM-CSF and TNF-alpha. This d egree of expansion translates into an effective yield of similar to 1. 7 x 10(6) mature dendritic cells per single mi of normal adult human b one marrow, compared with similar to 10(6) dendritic cells usually obt ained from 450 to 500 ml of peripheral blood. In addition to dendritic cells that constitute similar to 10 to 15% of the total myeloid proge ny, the cultures contain monocytes/macrophages and intermediate granul ocytic precursors. Monocytes/macrophages and dendritic cells together comprise all of the class II MHC-positive progeny. Sorted cells bearin g the CD14(+) HLA-DR(+) phenotype of mature monocytes are at least 1.5 to 2 logs less active than CD14(-) HLA-DR(+) dendritic cells as stimu lators in the allogeneic MLR, even though both CD14(+) and CD14(-) sub populations share expression of several costimulatory ligands, The syn ergistic combination of c-kit ligand, GM-CSF, and TNF-alpha therefore expands substantial numbers of immunostimulatory CD14(-) HLA-DR(+) den dritic cells from defined CD34(+) progenitors in human bone marrow. Th is should facilitate the use of dendritic cells in the manipulation of T cell-mediated immune responses.