MPN and B-cell malignancy coexist in Stat1^−/−mice. (A) Representative smears (BM, PB, original magnification: 40×; hematoxylin and eosin stainings) and photographs of spleens and livers. (B) Presence of Gr1⁺Mac1⁺ cells of wt and MPN⁺Stat1^−/− animals (FACS; BM, spleen). One representative example per genotype is shown in (A) and (B). (C) FACS analysis of Gr1⁺Mac1⁺ and CD19⁺ (spleen). One representative example per experimental group is shown. (D) Absolute cell numbers of CD19⁺ cells in BMs and spleens of transplanted mice (n = 3 each). Data represent means ± SD; BM cntrl vs BM Stat1^−/− recipient. **P < .01; ***P < .001). (E) Representative photographs of spleens of control (phosphate-buffered saline injected) and BMT mice.