Expression of Fas on ECFCs after incubation with rhIFNγ. Day-5 cells were cultured in liquid medium in the presence of rhIFNγ at 0 to 1,000 U/mL for 48 hours (A) or at 1,000 U/mL for 24 to 96 hours (B). At the indicated times, the cells were incubated with FITC-MoAb to Fas (CD95) or FITC-murine IgG1. Flow cytometric analysis was then performed. The open histogram shows the CD95 fluorescence of the cells incubated without rhIFNγ and the solid histogram shows the CD95 fluorescence of the rhIFNγ-treated cells. The purity of the day-7 cells was 89% ± 9% (A) and 81% ± 7% (B).