Figures 1–9.

Figure 1. Mast cell hyperplasia, pancreas, naïve mouse. (a) Large aggregates of mast cells surround the pancreatic ducts and adjacent islets. Inset: there is a high level of granulation in these cells. Hematoxylin and eosin (HE). (b) The absence of nuclear labeling with antibody to hNuMA1 indicates that the cells are of mouse origin. The cytoplasmic color is non-specific staining due to mast cell granules. Figure 2. Mast cell hyperplasia, pancreas, mouse implanted with transduced hCD34+ cells (mouse no. 15). (a) Interstitial infiltrates of mast cells are present throughout the pancreas. Inset: the mast cells are smaller, have fewer granules and are paler when compared to the mouse mast cells in Figure 1. (b) Positive nuclear labeling with antibody to hNuMA1 indicates that these cells are of human origin. (c) Metachromatic staining of granules with toluidine blue supports the identification of the cells as mast cells. Figure 3. Mast cell hyperplasia, pancreas, humanized mouse (mouse no. 10). The identity of the mast cells is confirmed by positive labeling for c-Kit/CD117 (a) and mast cell tryptase (b). Figure 4. Mast cell hyperplasia, pancreas, mouse implanted with an acute erythroid leukemia (AEL) xenograft (mouse no. 20). (a) The pancreas contains both foci of large highly granulated mouse mast cells (arrows) and interstitial infiltrates of smaller, more lightly granulated human mast cells (arrowheads). HE. (b) The human cells show positive nuclear labeling for hNuMA1 (arrowheads), and the mouse cells are negative for nuclear hNuMA1 (arrows). Figure 5. Eosinophil hyperplasia, bone marrow of vertebra, humanized mouse (mouse no. 1). The bone marrow contains patchy areas with markedly increased numbers of eosinophil precursors (example area circled). Inset: cellular detail of eosinophil granules. HE. Figure 6. Eosinophil hyperplasia, bone marrow of sternum, mouse implanted with transduced hCD34+ cells (mouse no. 15). The circled areas indicate patches of eosinophil precursors and the inset shows cellular detail. HE. Figure 7. Eosinophil hyperplasia, bone marrow of sternum, mouse implanted with an AEL patient-derived xenograft (PDX). HE. Figure 8. Eosinophil hyperplasia, bone marrow of sternum, mouse implanted with an AML PDX. HE. Figure 9. Immunohistochemical labeling of a section from the mouse in Figure 6. The cells are confirmed to be of human eosinophilic lineage by positive labeling for the human-specific major basic protein (MBP). Inset: no labeling for mouse-specific MBP.