Tracking of PKH26-labeled BM cells in vivo. Murine marrow cells (A) were labeled with PKH26 (B) and 10⁸ cells were injected into a lethally irradiated syngeneic mouse. Three hours later, PKH26⁺ cells that had “homed” to the bone marrow (C; 11% labeled) or spleen (D; 44% labeled) were identified by flow cytometry and sorted according to the gates depicted by the vertical lines.