Figure 5.

Application of exogenous granulocyte-macrophage colony-stimulating factor (GM-CSF) increases myeloid differentiation without affecting overall engraftment. (A) Schematic diagram of the experimental set up. Nine mice were transplanted intrahepatically with 1×10⁶ juvenile myelomonocytic leukemia (JMML) mononuclear cells of Patient #2. Five weeks later, human cell engraftment was confirmed by flow cytometry of CD45⁺ peripheral blood cells. Mice were divided into two experimental groups matched for level of engraftment in peripheral blood. Four mice received weekly injections of 5 μg recombinant human GM-CSF, while saline was administered in 5 mice. Applications were started eight weeks after transplantation. The animals were analyzed 12 weeks later. (B) The human CD45⁺ cell engraftment, the proportion of CD34⁺ progenitor cells and the proportion of CD33⁺ myeloid cells were determined in bone marrow (left) and spleen (right). Levels of human CD45⁺ and CD34⁺ cells were comparable between untreated (open symbols) and treated (filled symbols) animals. The proportion of CD33⁺ cells was significantly higher in bone marrow and spleen of treated animals (P=0.01, Mann-Whitney test).