Effect of duration of IFNγ incubation with day-5 ECFCs on reduction of ¹²⁵I-rhSCF–specific binding. Control cells not treated with rhIFNγ were incubated for the same periods of time at 37°C and then specific binding was determined as in Fig 1. Data are expressed as a percentage of the control and as means ± SD of three experiments. (★★) P < .001 between control cells and rhIFNγ-treated cells. ECFC purity was 61% ± 9% for control cells and 57% ± 5% for rhIFNγ-treated cells at 24 hours (P = .17), with no significant change in total cell concentrations over 24 hours (P < .5).