MPD is reproduced in Ptpn11^D61G/+ BM cell-reconstituted primary and secondary recipients. BM cells (1 × 10⁶) freshly harvested from 3-month-old Ptpn11^D61G/+ and WT littermates (CD45.2⁺) were directly transplanted into lethally irradiated BoyJ (CD45.1⁺) mice (noncompetitive repopulation assay; n = 3 and 7 for WT and Ptpn11^D61G/+ groups, respectively). White blood cell (WBC) counts in peripheral blood (A), percentages of neutrophils and lymphocytes (B), spleen weights (C), and percentages of donor cell-derived myeloid (Mac-1⁺/Gr-1⁺) cells in BM (D) and spleen (E) of the recipients were determined at 16 weeks or the indicated time points after the transplantation. BM cells (1 × 10⁶) harvested from 3-month-old WT or Ptpn11^D61G/+ littermates were transplanted with the same number of BoyJ BM cells into lethally irradiated BoyJ mice (n = 5 per group). Sixteen weeks after transplantation, WBC counts (F), percentages of neutrophils and lymphocytes (G), and spleen weights (H) of the recipient mice were determined. Spleens were photographed using a Canon PowerShot SD600 digital camera.