Effects of IFN-α2b and NIP-004 on human platelets and megakaryocytes in hu-NOG mice. Human cord blood–derived CD34⁺ cells were transplanted into immunodeficient NOG mice (hu-NOG). Three months after transplantation, human PEG-IFN-α2b was administered to hu-NOG mice 3 times weekly for 7 weeks. NIP-004 was administered daily to hu-NOG mice for 4 weeks, 3 weeks after initial treatment with PEG-IFN-α2b. (A) The number of human platelets was decreased by PEG-IFN-α2b in a dose-dependent manner. NIP-004 reversed the decrease in human platelets. By contrast, the number of murine platelets in hu-NOG mice was not changed because of the species specificity of human PEG-IFN-α2b and NIP-004. (B) DNA ploidy of human megakaryocytes in hu-NOG mice. Bone marrow cells collected from hu-NOG mice were stained with antihuman CD41a antibody and 7-AAD dye. The number of each ploidy in human megakaryocytes was measured by flow cytometry using Flow-Count Fluorospheres. Data are means plus or minus SEM from 5 mice (*P < .05 vs control; #P < .05 vs PEG-IFN-α2b 30 μg/kg).