In vivo marrow homing of mobilized KL and SKL cells. (A) The top histogram shows lineage markers (PE) and isotype staining of donor PBMNCs before transplantation. The bottom 2 plots show Sca-1 (PE-Cy7) vs c-kit (APC; right) and their isotype staining (left) in lin⁻ cells. M1: lin⁻ cells; R1: Sca-1⁺, c-kit⁺ cells in lin⁻ cells. (B) PBMCs mobilized by G-CSF or GROβ_Δ4 were stained with CFSE and 4 × 10⁷ cells were transplanted into lethally irradiated syngeneic recipients. Recipient marrow cells were harvested 16 hours after transplantation. The top plots show CFSE staining in nontransplanted recipient (left) and transplanted recipient marrow (right) stained with lineage markers (PE), anti-Sca-1 (PE-Cy7), and anti-c-kit (APC) antibodies. The R1 gate represents CFSE⁺ cells. The middle histogram represents lineage markers (PE) and isotype staining of CFSE⁺ cells. The bottom plots shows Sca-1 (PE-Cy7) vs c-kit (APC) staining and its isotype staining in the CFSE⁺ lin⁻ population. Gate R2 are Sca-1⁺ c-kit⁺ cells in CFSE⁺ lin⁻ cells. (C) Total KL or SKL cells in 2 × 10⁶ PBMCs homing to recipient marrow. Data are expressed as mean (± SEM) from 3 experiments using 30 donors and 3 recipients per group per experiment. *P < .05 compared with G-CSF.