Elimination of BM hematopoietic progenitor and stem cells. BM Lin^-Sca1⁺c-Kit⁺CD34⁺, Lin^-Sca1⁺c-Kit⁺CD34^-, and Lin^-Sca1⁺c-Kit⁺ cell proportions from 15 control and 15 BM failure mice were each multiplied by the total number of BM cells of each mouse, assuming that 2 tibiae and 2 femurs contained 25% of total BM cells, to calculate total cell numbers (top left). Two BM cell pools, each from 3 BM failure mice, and BM cells from 2 untreated control mice were tested for day 12 CFU-S, shown as total CFU-S per mouse (top right). BM cells pooled from 4 BM failure CByB6F1 mice were serial diluted from 1:2 to 1: 64, whereas BM cells from 2 untreated CByB6F1 control donors were diluted from 1:32 to 1:128, and each cell dilution was used to rescue 4 or 2 lethally irradiated (10 Gy) recipients. Recipient survival was monitored for 2 months (for those that received control BM) but only shown for 30 days here (bottom). Data presented in the top row are means with standard error bars.