Backgating of lineage marker–positive subsets reveals contrasting SP profiles. Provided for comparison is a corresponding whole BM SP profile with percentage of reserpine-sensitive SP (R-SP), intermediate SP (I-SP), and non-SP populations indicated (A; 100 000 events). Display of NK1.1⁺ (B; 2087 events) or CD5⁺ (C; 1154 events) lymphoid cells on Hoechst red/blue plots revealed an enrichment of the rare intermediate SP population. In contrast, Gr-1⁺ cells (D; 72 800 events) contained very few intermediate or SP cells and mostly non-SP cells.