Normal homing and localization of transplanted hematopoietic cells in recipient BM. (A) Frequencies and total numbers of homed BMNCs in recipient BM. BM cells pooled from 3 mice (CD45.1⁺) were injected into IR or NR recipients (CD45.2⁺). Seventeen hours after transplantation, BM cells were harvested and stained with anti-CD45.1 and CD45.2. The frequency of donor cells was then measured by flow cytometry. Total absolute number of donor cells was also calculated. **P < .01. n = 4. (B) Localization of the homed cells. CFSE-labeled Lin⁻c-kit⁺ cells were injected into IR or NR recipients that were scarified 17 hours after transplantation. The homed cells were identified on the sections of femurs based on CFSE staining with fluorescence microscopy. Images show the cells under a 490/20-nm filter (green, left), 555/28-nm filter (red, center column) and their overlay (right). Arrows indicate homed cells. The top panel was from a NR recipient, and the bottom panel was from an IR recipient. The photograph was taken under 40×/0.60 by a digital camera (RT Slider-Spot, model 2.3.1.1.) with Spot Version 4.0.9 software (Diagnostic Instruments). Adobe Photoshop CS Version 8.0 (Adobe System) and Microsoft Office PowerPoint 2003 software were used for image sizing and displaying. (C) Enumeration of the homed cells in proximity to the endosteal niche. Total homed cells from NR and IR recipients per section were counted, and the lodgment was quantified by the proportion of homed cells located within the endosteal region. **P < .01. n = 20 sections.