Dose- and time-dependent induction of Fas mRNA in ECFCs treated with rhIFNγ. Day-5 cells were incubated with IFNγ at 0 to 2,000 U/mL for 72 hours or with 2,000 U/mL for 0 to 72 hours, and then the total RNA was prepared. Twenty micrograms of total RNA was loaded in each lane. The blots were hybridized with a labeled probe for Fas and rehybridized with a probe for actin after stripping the initial probe. The ECFC purity at day 5 was 51% ± 9% and 56% ± 8%, respectively, and by day 8 it was 89% ± 6% and 91% ± 8%.