CD4⁺CD8⁺DP immature T cells appear 2 weeks after transplantation in bone marrow and spleen of BALB/c wt mice receiving syngeneic ICN1-transduced bone marrow cells. Cell suspensions from different organs were stained for the expression of CD4 and CD8 markers, and fluorescence-activated cell sorter (FACS) analysis was performed to determine EGFP⁺ and EGFP^- population percentages in bone marrow (BM; A), spleen (SPL; C), and thymus (THY; E) of mice that underwent reconstitution with bone marrow wt cells transduced with mICN1-(containing top panels) or empty retroviruses (bottom panels). Percentages of CD4⁺CD8⁺ cells in the EGFP⁺ (B,D; R2, left panels) and EGFP^- (B,D; R3, right panels) fractions from the same organs are indicated. Total yield of spleens is also included. Data are representative of at least 3 independent experiments.