Background CD34+ progenitor cells develop into tryptase+, CD117+ mast cells when cultured in the presence of recombinant human stem cell factor (rhSCF). However, spontaneous IgE receptor (FcɛRI) expression during human mast cell development is not well examined.
Objective Here, the expression and function of FcɛRI in and on human bone marrow-derived mast cells (HBMMCs) during development were investigated.
Methods and Results At 4 weeks of culture, predominant cells expressed high-affinity IgE receptor α chain (FcɛRIα) on the cell surface determined by flow cytometry, but CD117 was less expressed. Immunocytochemistry with antitryptase mAb and anti-FcɛRIα mAb revealed intracellular and surface expression of FcɛRIα at 2 weeks of culture, but tryptase was less expressed. FcɛRIα mRNA transcript preceded that of tryptase mRNA at 2 weeks of culture determined by real-time RT-PCR, and FcɛRIα, FcɛRIβ, FcɛRIγ, and tryptase mRNA increased along with differentiation. FcɛRIα cross-link on HBMMC and 4-week-old mast cells/mast cell precursors induced the release of IL-5 and granulocyte macrophage-colony stimulating factor, which was enhanced by rhSCF.
Conclusion These data indicated that HBMMC constitutively and spontaneously expressed functional FcɛRI subunits at the early stage of differentiation, probably because of the differences in the ability and functional property of progenitors.