Flow cytometric analysis of murine BM cells of NOD/SCID recipients of CFSE-stained xenografts of human CD34⁺ cells.

Human BM CD34⁺ cells were stained with CFSE and transplanted into conditioned NOD/SCID recipients. At 40 hours AT, mice were killed, and BM cells were stained with PE-conjugated immunoglobulin G₁ (isotype control, dot plot A) or PE-conjugated CD34 (dot plot B) and analyzed flow cytometrically. CFSE fluorescence was detected on the x-axis and that of PE on the y-axis. Dot plot A shows CFSE⁺ cells with background level of PE fluorescence (identified by the horizontal cursor) clearly distinguishable from murine CFSE⁻ BM cells. In dot plot B, which displays light scatter gated events from a listmode file containing 1.5 × 10⁵ events, a prominent population of CFSE⁺CD34⁺ cells can be identified. The percentage of cells contained in pertinent quadrants is given below each dot plot. Sort windows R1 and R2 in dot plot B were used to isolate CFSE⁺CD34⁺ and CFSE⁺CD34⁻ cells, respectively. Please note that the width of the sorting windows R1 and R2 was sufficient to include all detectable CFSE⁺ cells regardless of their proliferative history in the BM of recipient mice.