LT-HSC engraftment after BM transplantation is significantly impaired after hematopoietic cell depletion. (A) Peripheral blood analysis 48 hours after a single injection of 100 ng DT showed a significant depletion of leukocytes and platelets. (B) Pictogram describing a secondary transplant assay that used a GFP⁺ BM donation to DT-depleted and irradiated primary recipients. Primary BM was then transplanted along with WT competitor BM into irradiated WT secondary recipients. Bone marrow analysis for the presence of GFP positivity was performed at 16 weeks to evaluate the effectiveness of primary recipient LT-HSC engraftment defined as >1% GFP. (C) Flow cytometric analysis of mouse BM 16 weeks after secondary transplant assay evaluating the LT-HSC engraftment. WBC, white blood cell count.