Expression of FLT3 on CD34⁺ cells (left-hand panel) and coexpression of CD38 and FLT3 on CD34⁺ BM cells (right-hand panel). For analysis of FLT3 expression, BM MNC cells were stained simultaneously with HPCA-2–FITC and BV10-PE. Cells within region 1 (R1) were considered as CD34⁺FLT3⁺ and those in region 2 (R2) were considered as CD34⁺FLT3⁻. The right-hand panel shows expression of CD38 (FITC) and FLT3 (PE) on CD34⁺ cells enriched by 561-Dynal bead enrichment. The cell suspension contained 98.6% CD34⁺ cells. The quadstat is positioned to indicate the level of PE staining observed with the IgG-PE control.