Morphologic changes in BM of GCV-induced thrombocytopenic mice. (A) BM of a HαIIbtk transgenic mouse. No megakaryocytes are present and cells from the erythrocytic lineage are decreased. Granulocytic cells such as neutrophiles (★) predominate in this BM compartment showing that the granulocytic lineage is unaffected. Large increase on the amount of macrophage-like cells (M) showing phagocytic activity in their cytoplasm was seen. Bar = 5 μm. (B) Section of BM obtained from a GCV-induced thrombocytopenic MαIIbtk mouse having several copies of the transgene integrated. Mature cells of the megakaryocytic, erythrocytic, and granulocytic lineage are severely decreased. Large macrophage-like cells with dense bodies suggesting phagocytic activity invade the BM. Cytoplasmic processes extend around the few resting hematopoietic cells. Poorly differentiated mononuclear cells (*) with high nucleocytoplasmic ratio, having the morphology of progenitor cells, seem to be present in higher amounts. Bar = 5 μm.