Abstract

Human mast cells are known to arise from a CD34+/c-kit+ progenitor cell population that also gives rise to neutrophils, eosinophils, basophils, and monocytes. To further characterize cells within the CD34+/c-kit+ population that yield mast cells, this progenitor was additionally sorted for CD13, a myeloid marker known to appear early on rodent mast cells and cultured human mast cells, but not expressed or expressed at low levels on human tissue mast cells; and cultured in recombinant human (rh) stem cell factor (rhSCF), rh interleukin-3 (rhIL-3; first week only), and rhIL-6. Initial sorts revealed that although the majority of cells in culture arose from the CD34+/c-kit+/CD13−cell population, mast cells arose from a CD34+/c-kit+/CD13+progenitor cell that also gave rise to a population of monocytes. Sequential sorting confirmed that CD34+/c-kit+/CD13+cells in CD34+/c-kit+/CD13−sorts gave rise to the few mast cells observed in CD13−sorted cells. CD34+/c-kit+/CD13+cells plated as single cells in the presence of various cytokine combinations gave rise to pure mast cell, monocyte, or mixed mast cell/monocyte progeny. Addition of either rh granulocyte-macrophage colony-stimulating factor (rhGM-CSF) or rhIL-5 to the CD34+/c-kit+/CD13+progenitor cell population cultured in rhSCF, rhIL-3, and rhIL-6 did increase the number of total cells cultured and in the case of rhIL-5, did increase total mast cell numbers. Neither rhGM-CSF or rhIL-5 led to additional cell populations, ie, even with the addition of rhGM-CSF or rhIL-5, only mast cells and monocytes grew from CD34+/c-kit+/CD13+cells. Thus, human mast cells and a population of monocytes arise from precursor cells that express CD34, c-kit, and CD13; and within which, are mast cell, monocyte, and mast/monocyte (bipotential) precursors.