GUSB activity correlated with human CD45 expression in a flow cytometric assay on the bone marrow of NOD/SCID/MPSVII mice that received transplants of human CD34⁺ cells.

(A) Bone marrow from a NOD/SCID/MPSVII mouse that did not receive a transplant when incubated with a fluorescent substrate for GUSB followed by staining with an antihuman CD45 antibody showed slight background on the GUSB channel (2.6%). Minimal staining on the human CD45 channel was found (0.3%). (B) In similarly assayed bone marrow from a NOD/SCID/MPSVII mouse 12 weeks after the transplantation of cord blood CD34⁺ cells, only the population positive for human CD45 had significant GUSB activity. Cells negative for human CD45 displayed a level of GUSB activity (2.7%) comparable to that of the control NOD/SCID/MPSVII bone marrow (A).