['Mast cells have been regarded as a potential source of cytokines. Although the human mast cell line HMC-1 and human lung mast cells have been shown to produce interleukin (IL) 13, it still remains uncertain whether cord-blood-derived human cultured mast cells produce IL-13.', 'Human cultured mast cells were raised from cord blood cells in the presence of stem cell factor (SCF) and IL-6. Levels of IL-13 mRNA were examined by a semiquantitative reverse transcriptase-polymerase chain reaction. IL-13 levels in the supernatants were measured with an enzyme-linked immunosorbent assay.', 'When the IgE-sensitized cultured mast cells were activated with anti-IgE, mRNA for IL-13 was amplified with a peak at 3 h after the stimulation. IL-13 was not detected in the supernatants of the activated mast cells in the absence of SCF, whereas the mast cells secreted significant amounts of IL-13 after the stimulation in the presence of SCF. Calcium ionophore A23187 also stimulated the mast cells to release IL-13 into the supernatant in the presence of SCF.'] Do cord-blood-derived human cultured mast cells produce interleukin 13 in the presence of stem cell factor?