C-kit ligand induction of immature neutrophils in cultures of human umbilical cord blood

Human cord blood cells cultured in suspension with soluble c-kit ligand produce immature mast cells from their agranular precursors; cocultures of cord blood and mouse 3T3 fibroblasts produce fully mature human mast cells. We noted cells of the neutrophil lineage in the c-kit ligand-supplemented suspension cultures. Similar cultures were prepared from individual cord bloods with several sources of the c-kit ligand, including mouse fibroblast conditioned media, a partially purified mouse 3T3 fibroblast factor(s), recombinant human stem cell factor, recombinant murine mast cell growth factor, and were sampled sequentially for routine and cytochemical ultrastructural studies. These studies show that peroxidase-positive azurophilic granule-containing neutrophilic myelocytes develop in quantity from their agranular precursors in cord blood when the c-kit ligand is present, but little to no maturation to mature neutrophils with specific granules occurs. Specific granules were also absent in the neutrophil precursors. The effect of c-kit ligand in vitro on two cell lineages in man is similar - i.e., it permits the development of immature cells to differentiate from their agranular precursors in cord blood, but complete maturation to fully mature mast cells or neutrophils does not occur.