Quantification of bioluminescent signals in mice that received transplants of luciferase-transduced human CD34⁺ and CD34⁺CD38^- cells. Summary of data from 5 animals that received transplants of CD34⁺ cells and 3 animals receiving CD34⁺CD38^- cells in 3 separate experiments showing quantification of photon flux from each entire animal plotted against the number of days after transplantation. Means and SDs are presented. From day 36, mean signal from animals that received CD34⁺CD38^- transplants was significantly higher than mean signal from those that received CD34⁺ transplants (P < .05). Data from only one CD34⁺ animal are available on days 72 to 108. On days 1, 3, 6, and 10, mice that received transplants of CD34⁺CD38^- cells were not imaged. Control is a mouse that did not receive a transplant, after intravenous injection of luciferin. ▪ indicates CD34⁺; □, CD34⁺CD38^-. sr indicates steradian.