Dose-response curves for the multilineage effect of TPO administered IV immediately after 6 Gy TBI. Peripheral blood cell counts 10 days after 6 Gy TBI. Values are means ± SD, n = 6 for the doses of 0.01, 0.03, and 0.1 μg and n = 12 for the dose 0.3 μg/mouse. The vertical line in the upper panel represents the dose level of 0.15 μg/mouse, which results in 50% saturation of c-mpl on platelets. The placebo control levels coincide with the level at which the horizontal axis is set.