TPO overexpression causes a comparable elevation in platelet and nucleated blood cell numbers and an anemia in hosts engrafted with TPO virus–infected BM cells from WT or

opg^−/− donors. Results are presented as the mean ± SD of 7 to 10 animals per experimental group. WT hosts engrafted with WT BM cells are shown with open triangles (▵); WT hosts engrafted withopg^−/− BM cells are shown with filled triangles (▴); opg^−/− hosts engrafted with WT BM cells are shown with open squares (■); andopg^−/− hosts engrafted withopg^−/− BM cells are shown with filled squares (▪). (A) TPO in plasma was measured with an enzyme-linked immunosorbent assay (ELISA) at 1, 2, and 3 months after transplantation. Values in normal WT or opg^−/−controls were 0.46 ± 0.05 ng/mL (n = 12). (B) Platelet numbers during the 3 months of follow-up. (C) Total numbers of nucleated blood during the follow-up. (D) Hematocrit values.