Fig. 1.
Development of erythroleukemia after transplantation with bcr/abl-expressing C/EBPα−/− cells. (A) Wright-Giemsa staining of blood smears from mice transplanted with bcr/abl-expressing C/EBPαpos cells (panel 1), showing an increase in granulocytes (arrows), and bcr/abl-expressing C/EBPα−/− cells (panel 2), showing the appearance of erythroblasts (arrows). (Magnification: ×1,000.) (B) Expression of bcr/abl protein in 5 × 105 BM cells from mice transplanted with cells as indicated. The membrane was probed with an anti-c-abl antibody. (C) Cytospin of BM from mice after transplantation with bcr/abl-expressing cells. Note the predominance of granulocytic cells in the presence of C/EBPα (panel 1) and the accumulation of immature erythroid cells in the absence of C/EBPα (panel 2). Some mice also had an increase in mast cells (panel 3). (Magnifications: ×1,000, panels 1 and 2; ×400, panel 3.) (D) Histology of BM and spleen from mice after transplantation with bcr/abl-expressing cells demonstrating disruption of normal architecture. Hematoxylin and eosin (H&E) stain (panel 1) and MPO stain (panel 2) show extensive granulocytic, MPO-positive infiltration after transplantation of C/EBPαpos cells. Hematoxylin and eosin stain of a spleen from a mouse transplanted with C/EBPα−/−cells demonstrates the predominance of immature erythropoiesis (panels 3 and 4). Complete absence of mature myeloid elements in BM of these mice was confirmed by MPO immunostaining (panel 5). Accumulation of mast cells was detected by immunhistochemistry for mast cell tryptase (panel 6). (Magnifications: ×1,000, panels 1 and 4; ×400, panels 5 and 6; ×200, panels 2 and 3.) (E) Flow cytometric analysis of BM from bcr/abl-expressing C/EBPα−/− cells. The immunophenotype of the GFP+ cells is shown. The percentage of cells in each quadrant is indicated. (Left) In the absence of C/EBPα, no mature myeloid elements were detected. (Center) Instead, an accumulation of TER-119+ erythropoietic precursors was observed. (Right) Analysis of differentiation status of erythroid cells by staining with CD71 and TER-119 (9) demonstrated an increase in erythroid precursors (TER-119highCD71 high).