Histologic sections of spleen and femur from mice engrafted with WT or TGF-β1^−/− virus–infected hematopoietic cells.

Three mice in each group (WT5, WT8, WT14 and KO8, KO11, KO14) were killed 4 months after transplantation. Representative sections are shown. Spleen sections stained by hematoxylin and eosin from (A) WT5 engrafted with TGF-β1^+/+ cells and (B) KO14 engrafted with TGF-β1^−/− cells show the hyperplasia of megakaryocytes and granulocytes. Silver staining revealed massive fibrosis in spleen sections from WT5 (C), whereas no significant reticulin deposition was detected in KO14 (D). Longitudinal femur sections stained by hematoxylin and eosin from WT5 (E) show the growth of new bone trabeculae within the marrow cavity and from KO14 (F) where no bone growth was detected. Silver staining of a femur section from WT5 (G) showing myelofibrosis and from KO14 (H) shows no deposition of reticulin fibers. Original magnifications: A-D, × 400; E-H, × 250.