Flow cytometry, immunohistochemistry, and casting analyses of the endothelial cell composition in LDSAC and HDSAC populations. Representative flow cytometry evaluation of endothelial cells either from LDSAC or HDSAC cultures in the late stage of Friend disease. (A) The chosen region (R1) from the total cell population, negative for CD45, either from HDSAC or LDSAC adherent cell populations. (B) The percentage of gated R1 cells that are positive for flk-1 (M1) in the HDSAC population. (C) The percentage of gated R1 cells that are positive for fetal liver kinase-1 (flk-1) (M1) in the LDSAC population. Immunohistochemistry of VE-cadherin stained with 3′3-diaminobenzidine DAB (red) and counterstained with hematoxylin for blood vessel detection was performed on healthy and erythroleukemic spleen sections as described in “Materials and methods” (D,F, respectively). Casting images were performed according to “Materials and methods” on healthy and erythroleukemic spleens in late-stage disease (E,G, respectively).