Immunofluorescent detection of SCF on retroviral producer cells. Fibroblasts were stained with FITC-conjugated antibody to human SCF with (A through C) or without (D and E) permeabilization and viewed under the fluorescence microscope (×400). (A) 1MI cells following transfection but before selection in histidinol; (B) 1MI-▵SCF cells following selection and cloning; (C) untransfected 1MI cells. (B) and (C) were photographed under exactly the same exposure conditions; (D) 1MI-▵SCF cells following selection and cloning; (E) untransfected 1MI cells. (E) Is overexposed to make the cells more visible.