Expression of Mac-1 on long-term reconstituting stem cells from normal and 5-FU–treated bone marrow. Erythrocyte-depleted WBM was collected from normal and 5-FU–treated mice, stained with anti–Mac-1, and sorted into 3 populations as indicated (A, normal; C, 5-FU); the relative representation is shown as a percent within each gate. WBM cells from normal mice were sorted into Mac-1⁻ (32% of bone marrow), Mac-1^low (15%), and Mac-1^high (53%) populations from Ly5.2-expressing mice. The equivalent of 2 × 10⁵ WBM cells from each population was injected into irradiated Ly5.1 recipients in competition with 2 × 10⁵ Ly5.1 WBM cells. Thus, 0.64 × 10⁵ cells of the Mac-1⁻ population were injected per recipient, 0.3 × 10⁵ cells of the Mac-1^low population per recipient, and 1.06 × 10⁵ cells of the c-kit^high population per recipient. The equivalent populations were sorted from 5-FU–treated Ly5.2 mice and 0.62 × 10⁵ cells of the Mac-1⁻ cells, 0.22 × 10⁵ of the Mac-1^low cells, and 1.16 × 10⁵ of the Mac-1^high cells were injected per irradiated Ly5.1 recipient in competition with 2 × 10⁵ Ly5.1 WBM cells. Recipient mice were assayed for donor-type reconstitution after at least 16 weeks postreconstitution and the percent of donor-derived cells in each lineage was determined for each recipient of Mac-1⁻, Mac-1^low, or Mac-1^high cells (B, normal; D, 5-FU). The long-term reconstitution data for mice that received 5-FU–treated bone marrow represents the sum of 2 independent experiments with 5 mice in each group.