Net effect of PI3Kδ deficiency for leukemia development. (A) Kaplan-Meier plot of PI3Kδ^+/− recipients after injection of PI3Kδ^+/−v-abl–transformed cells and of PI3Kδ^−/− recipients after injection of PI3Kδ^−/−v-abl–transformed cells. Matching genotypes of recipient animals with the genotype of the injected cell line abolished any differences in leukemia onset and progression (log-rank test; P = .95). (B) Accordingly, upon v-abl infection of newborn PI3Kδ^+/− and PI3Kδ^−/− recipients, no significant difference in survival kinetics was detected (log-rank test; P = 0.7). No differences were observed between PI3Kδ^+/+ and PI3Kδ^+/− control animals, as verified in an independent experiment (data not shown). (C) H&E-stained histologic sections of infiltrated bone marrow (top row), spleen (middle row), and liver (bottom row) of PI3Kδ^+/− and PI3Kδ^−/− animals that had been challenged with v-abl at the newborn age (magnification, ×100, Zeiss AxioImager 21, 10× objective, NA 0.25, air, camera: Pixelink Color, 1600 × 1200; software: PixelINK Capture 3.0).