Receptor expression, mediator release, histamine content, and morphology of cells cultured in SCF and IFN-γ, IL-4, or IL-5. (A) CD34⁺ cells were cultured for 8 weeks, then stained with anti–FcϵRI-FITC mAb. (Numbers indicate percentage of positive cells from 1 representative experiment; n = 5.) (B) Cells cultured in SCF (black bars), SCF + IFN-γ (light gray bars), SCF + IL-4 (white bars), and SCF + IL-5 (dark gray bars) were sensitized with IgE overnight, then stimulated with increasing doses of antigen and β-hexosaminidase (B), and tryptase (C) release was measured. (D) Cytospin preparations were stained with toluidine blue to observe mast cell morphology (from 1 representative experiment; n = 5). (E) Histamine content was measured using ELISA. Asterisks indicate significance as measured by paired 2 sample t test (P > .01). Data in graphs are presented as the mean ± SEM (n = 5).