Regeneration pattern of platelets in mice irradiated with 6 Gy TBI and treated with 0.3 μg/mouse of TPO 24 hours after TBI (□), 2 hours after TBI (▪), or placebo (○), data from one representative experiment, n = 3 per data point. The shaded area represents the mean platelet counts ±SD of 19 normal mice (1123 ± 89). *P < .0001 compared with control mice;^#P < .0001 compared with mice treated 24 hours after TBI.