CD200 is a marker of LSC activity measured by xenotransplantation assays. (A) Schematic of experimental protocol showing cell sorting strategy based on CD45 and CD200 expression followed by transplantation into NSG mice. (B) Sorting gates and level of human CD45⁺ engraftment in injected femur following transplantation at indicated doses of sorted populations from 4 representative AML samples expressing CD200 on ≥10% of CD45^dim blasts (AML5, AML13, AML21, and AML47). (C) LSC frequencies in CD45^dimCD200⁺ blasts and CD3⁻CD19⁻ MNCs for samples AML13 and AML21, calculated using ELDA (extreme limiting dilution analysis) software. (D) Sorting gates and level of human CD45⁺ engraftment in injected femur following transplantation at indicated doses of sorted populations from a representative AML sample expressing CD200 on <5% of CD45^dim blasts (AML27). For panels B and D, each symbol represents 1 mouse; red symbols indicate leukemic grafts, green symbols indicate multilineage grafts, black symbols indicate no engraftment; mean ± standard deviation is shown for each cohort of mice.