Enhanced long-term engraftment capacity of p190-B^−/− FL cells. (A) WT and p190-B^−/− FL cells (0.4 × 10⁶ CD45.2⁺ FL) plus 1.6 × 10⁶ BM congenic competitor (CD45.1⁺) cells were injected into lethally irradiated recipient mice. The number of CD45.2⁺ versus CD45.1⁺ cells in the PB was determined between one and 6 months. Histograms show the percentage of CD45.2⁺ cells (left panel) and the absolute number of CD45.2⁺ cells (right panel) in the PB at the indicated time points after transplantation (mean ± SD; n = 24). *P < .05. (B-C) Serial transplantation of WT and p190-B^−/− FL cells. Average percentage of CD45.2⁺ cells in PB (B) and BM (C) 4 months after transplantation of primary, secondary, and tertiary recipients. Data are mean ± SD; n = 6 to 10 (1 representative experiment from 3 independent experiments all with similar results). (D) Flow cytometric analysis dot plot of LSK frequency in CD45.2⁺ BM cells from secondary recipient. Data shown are the frequencies of LSK cells (mean ± SD; n = 6). *P < .01. (E) Frequency of LSK (left panel) and LK cells (right panel) in CD45.2⁺ BM cells of primary and secondary recipients 4 months after transplantation. Data are mean ± SD; n = 6 to 10 (1 representative experiment from 3 independent experiments all with similar results).