SELECTIVE GROWTH OF HUMAN MAST-CELL INDUCED BY STEEL FACTOR, IL-6, AND PROSTAGLANDIN E(2) FROM CORD-BLOOD MONONUCLEAR-CELLS

To establish the method for generating a large number of mature human mast cells, we cultured cord blood mononuclear cells (CBMC) in several conditions in the presence of Steel factor (SF). Among several cytoki nes tested, IL-6 enhanced SF-dependent mast cell growth from purified CD34(+) cells for more than 8 wk in culture. When CBMC were cultured i nstead of CD34(+) cells, IL-6 enhanced the mast cell development in th e presence but not in the absence of PGE(2). PGE(2) enhanced the SF- a nd IL-6-dependent development of mast cells from CBMC probably by bloc king granulocyte-macrophage CSF (GM-CSF) secretion from accessory cell s, because 1) PGE(2) or anti-GM-CSF enhanced the mast cell development induced by SF and IL-6 from CBMC, but not from CD34(+) cells; 2) GM-C SF inhibited the enhancing effect of IL-6 on the mast cell development from CD34(+) cells; and 3) PGE(2) inhibited CM-CSF secretion from CBM C. The mast cells cultured in the presence of SF, IL-6, and PGE(2) for >10 wk were 99% pure, and seemed to be functionally mature, because 1 ) they contained 5.62 mu g of histamine and 3.46 mu g of tryptase per 10(6) cells; and 2) when sensitized with human IgE and then challenged with anti-human IgE, the cells released a variety of mediators such a s histamine, and an increase in intracellular Ca2+ was found in advanc e of the activation of membrane movement by using a confocal laser-sca nning microscope. Electron-microscopic analysis revealed that some of the cultured mast cells are morphologically mature since they filled w ith scroll granules and contained crystal granules.