Fluorescent In Vivo Tracking of Hematopoietic Cells

We report a new technology for in vivo tracking of hematopoietic cells, using fluorescent lipophilic probes. Because the probe is irreversibly bound in the lipids of the cell membrane. substantial numbers of dye molecules can be incorporated per cell and thus substantial signal to noise can be achieved. Although this technology can be used for all hematopoietic cells, these first findings are reported on red blood cells (RBCs) owing to the importance of the membrane to RBC function and integrity. We demonstrated that labeling 10% of the RBCs of a rabbit and reinjecting them into the animal makes possible the tracking of these cells at various times after injection. Further-