Induction of differentiation of human mast cells from bone marrow and peripheral blood mononuclear cells by recombinant human stem cell factor/kit-ligand in long-term culture

interleukin-3 [IL-3], IL-4, and stem cell factor [SCF]) promote the growth of mast cells (MCs). However, so far little is known about factors controlling differentiation of human MCs. Recent data suggest that human MCs express receptors (R) for SCF. The aim of the present study was to investigate whether recombinant human (rh) SCF induces differentiation of human MCs from their precursor cells. For this purpose, bone marrow (BM; normal donors, n = 6) and peripheral blood (PB; normal donors, n = 11) mononuclear cells (MNC) were cultured in the presence of rhSCF, rhlL-3, rhlL-4, rhlL-9, recombinant human macrophage colonystimulating factor (rhM-CSF), or control medium in long-term (8 weeks) suspension cultures. After 4 weeks, up to 5% Of the MNC (BM and PB) cultured in the presence of rhSCF, but not in the presende of other cytokines, were found to exhibit the characteristics of MCs. These MCs expressed the YB5.B8reactive domain of the SCF R as well as IgE R, as determined by combined toluidine blue/immunofluorescence staining. ROWTH and differentiation of hematopoietic (progenG itor) cells is regulated by a complex network of cytokines and a variety of microenvironmental factors.'" Recently, a novel hematopoietic growth factor, stem cell factor (SCF), has been identified.4-s SCF is primarily produced by stroma cells. The mature protein is either expressed on the stroma cell surface or released to act as a soluble (growth) fact~r.~,~ The membrane-bound form of SCF is determined by tissue-specific, alternative splicingy and may act as a local growth hormone or/and as a homing receptor for hematopoietic (progenitor) cells expressing receptor (R) for SCF. A number of previous and more recent observations suggest that in the murine system, SCF is involved in growth and differentiation of mast cells (MCS).~O-'~ MC-deficient SI/Sld mice exhibit a defect of the microenvironment,1° and the defect has been mapped to the gene (located in the Steel locus [SI]) encoding for SCF." Administration of SCF (also termed steel factor [SF] or MC growth factor [MGF]) may repair MC deficiency in SI/Sld mice in local areas6 More recent studies have shown that recombinant SCF (rSCF) induces in vivo growth and differentiation of MCs in normal mice12 as well as growth and differentiation of murine MCs in vitro.6J2