Competitive grafts in recipient mice transplanted with 3-month-old donor mice showing proliferative advantage of KI cells over WT cells. (A) Percentage of CD45.2⁺ blood myeloid (CD11b⁺ or Gr-1⁺) and lymphoid (B220+ or CD3+) cells from KI or WT origin in recipient mice showing progressive overgrowth of KI cells in competitive grafts. CD45.1 recipient mice were transplanted with either 100% KI cells (CD45.2) (■, dashed line, n = 5) or a mixture of 30% KI cells (CD45.2) plus 70% WT CD45.1+2 cells (●, solid line, n = 5). As a control, CD45.1 recipient mice were transplanted with a mixture of 30% WT CD45.2 cells and 70% WT CD45.1+2 cells (○, dashed line, n = 5). (B) Percentages of CD45.2⁺ cells from KI or WT origin in blood and tissues analyzed 34 weeks after competitive grafts showing progressive overgrowth of KI cells in late and early stages of differentiation. CD45.1 recipient mice were transplanted with either 100% KI cells (CD45.2) (black columns) or a mixture of 30% KI cells (CD45.2) plus 70% CD45.1+2 WT cells (gray columns). As a control, CD45.1 recipient mice were transplanted with a mixture of 30% WT CD45.2 cells plus 70% WT CD45.1+2 cells (white columns). (B-1) CD45.2, Gr-1, CD11b, B220, and CD3-positive cells were determined in blood. (B-2) Spleen weight (g) and marrow cellularity (×10⁶ cells/femur) in recipient mice. (B-3-4) CD45.2⁺, Lin-, LSK, and SLAM (LSK, CD48⁻, CD150⁺) cells were determined in BM (3) or spleen (4). ** indicates that the numbers of SLAM cells detected in the WT spleen samples were too low (10 ± 5 cells) to provide a reliable value. Data are mean values ± SEM, n = 3. *P ≤ .05 with the 2-tailed unpaired Student t test.