Engraftment of G-CSF–mobilized human peripheral blood CD34⁺ cells in sublethally irradiated NOD/SCID mice. The percentage of human cells in (A) BM, (B) spleen, and (C) PB was determined by flow cytometry at 6 to 8 weeks after transplantation. Open circles represent untreated animals, closed circles represent animals treated with human G-CSF, triangles indicate animals treated with G-CSF and SCF (see Materials and Methods for dosage). Number of animals depicted in (A) through (C) is 81, 38, and 75, respectively. (D) Mean level of bone marrow engraftment (± SD) in five individual experiments spanning the range of the number of CD34⁺cells injected. Number of animals: in experiments 1 and 2, n = 6; in experiments 3 through 5, n = 4.