Improved T-ALL engraftment in NSG compared with NS122 recipients. (A) Irradiated NSG mice were injected intrafemorally with 1 × 10⁴ to 1 × 10⁷ T-ALL cells from 5 patients. RF cells from xenografts were analyzed by flow cytometry to determine engraftment and the percentage of human CD45⁺CD7⁺CD5⁺ cells. Each dot represents the percentage of CD45⁺CD7⁺CD5⁺ cells for each NSG recipient, with the bar representing the mean percentage for the T-ALL sample. (B) NS122 and NSG mice were injected intrafemorally with T-ALL 7017 at the cell doses indicated. RF cells from xenografts were analyzed by flow cytometry to determine engraftment and the percentage of human CD45⁺CD7⁺CD5⁺ cells. Each dot represents the percentage of human CD45⁺CD7⁺CD5⁺ cells for one recipient, with the bar representing the mean percentage for the cell dose. T-ALL 7017 did not engraft in NS122 mice but engrafted in NSG recipients. (C) T-ALL cells (7017) were sorted for CD7 and CD1a expression. Irradiated NSG mice were injected intrafemorally with 1 × 10⁵ to 2 × 10⁵ CD7⁻, CD7⁺CD1a⁻, or CD7⁺CD1a⁺ cells. Flow cytometric analyses of RF cells recovered from 3 NSG mice injected with 7017 T-ALL CD7⁻ cells are shown in the top 3 rows, and one NSG recipient of 7017 CD7⁺CD1a⁻ cells is shown in the bottom row. The panels show RF human CD45⁺ cells (left column) from xenografts coexpressing surface CD3 and TCRαβ (middle left column), CD4 and CD8 (middle right column), and HLA-DR and CD19 (right column). Human CD45⁺ cells in CD7⁻ recipients did not express surface CD3, TCRαβ, CD4, or CD8, indicating that these are not mature T cells. Some cells expressed surface CD19 and HLA-DR (right column, second, and third panels), suggesting that these cells are derived from the B cell lineage. RF cells from engrafted CD7⁺CD1a⁻ NSG recipient (bottom row) are CD4⁺CD8⁺ DP, consistent with the immunophenotype of the 7017 patient leukemia.