Analysis of bone marrow cellularity and extramedullary hematopoiesis after GCV withdrawal. (A) Col2.3ΔTK mice were treated with PBS or GCV for 45 days, after which the treatment was stopped. At different days after the withdrawal of treatment, animals were killed and their bones were evaluated histologically for their ability to reconstitute bone marrow cellularity. Paraffin section were stained with hematoxylin and eosin, and microphotographs were taken at an original magnification of 10 ×. (B) Animals were treated with ganciclovir or PBS as described. Spleen and liver suspensions were evaluated by their ability to generate myeloerythroid colonies in methylcellulose at different time points after withdrawal of treatment.