Transplantation with WT BM rescues lymphopenia. (A) Donor WT cells (Ly5.1) were transplanted into either WT or Lin28b mice and an engraftment assay was performed at 24 weeks after transplantation (n = 6 Lin28b recipients, n = 5 WT recipients). (B) Lymphocyte engraftment after transplantation at the indicated time points. White bars indicate WT; and black bars, Lin28b. (C) Quantification of naive (CD62L⁺CD44⁻), central memory (CD62L⁺CD44⁺), and effector memory (CD62L⁻CD44⁺) CD4⁺ cells in the peripheral circulation. (D) Quantification of naive, central memory, and effector memory CD8⁺ cells. White bars indicate WT; and black bars, Lin28b. (E) Percentage of WT (n = 3) or Lin28b (n = 3) recipients free of PTCL after transplantation of WT BM cells (C3, n = 12; D4, n = 16). Mice that died of causes other than PTCL were not included in this analysis (WT, n = 2; Lin28b, n = 3; C3, n = 5; D4, n = 3).