The role of CD9 on homing of cord blood CD34⁺ cells in NOD/SCID mice. (A) Cord blood CD34⁺ cells were cultured in the presence of an anti-CD9 mAb (ALB6; 10 μg/mL) or an isotypic mAb (IgG; 10 μg/mL) for 4 hours, and injected intravenously into NOD/SCID mice (1.9 × 10⁵ to 5 × 10⁵ cells per mouse). Bone marrow (BM) and spleens (SP) of recipient mice were analyzed for the presence of human CD45⁺CD34⁺ cells by flow cytometry 20 hours after transplantation (n = 11). P values are indicated. Right panel, representative flow cytometry analysis plots of human cell detection in BM and SP samples of transplanted mice. BM and SP samples from a mouse stained with isotypic antibodies (Iso) are also presented. The gates used for identification of human CD45⁺CD34⁺ cells and the frequency of human cells are indicated. (B) CD34⁺ cells were pretreated with IgG or ALB6, and transplanted into anti-CD122 (α-CD122)-treated or untreated NOD/SCID mice (n = 4). (C) Sorted CD34⁺CD9⁻ or total CD34⁺ cells (8.7 × 10⁴ to 2.1 × 10⁵ cells/mouse) were transplanted into NOD/SCID mice (n = 6). Homing level of each population was determined by flow cytometry. (D,E) CD9 expressions in (D) total CD34⁺ cells (n = 9) or (E) sorted CD34⁺CD9⁻ cells (n = 8) before injection were compared with those homed to BM and SP in NOD/SCID mice. Right panels, representative dot plots showing CD9 expression on injected and homed CD34⁺ cells. The percentage of cells in each quadrant is depicted.