Figures 21–23.

NSG-SGM3 mice implanted with acute erythroid leukemia (AEL) patient-derived xenografts (PDX). Figures 21 and 22. Engraftment of human leukemia cells, mouse no. 20. Figure 21. Bone marrow. (a) The marrow is filled with a homogeneous population of leukemic cells and occasional, scattered pigment-containing macrophages. HE. (b) The erythroid leukemic cells are positive for GATA1. Figure 22. Macrophage proliferation, liver. (a) There are aggregates of large macrophages with prominent cytoplasmic pigment. HE. Inset: cells are positive for hNuMA1. (b) The cells include multinucleated giant cells. Inset: intracytoplasmic erythocytes indicating erythrophagocytosis. HE. (c) The cytoplasmic pigment stains positively for iron. Prussian blue. (d–h) The cells are immunolabeled for hCD68 (d) and hCD163 (e) and are surrounded by mouse F4/80-positive cells (f). Admixed within these aggregates are low numbers of leukemic cells, identified by positive GATA1 labeling (g). Surprisingly, this mouse showed no CD3-positive T cells (h); the brown pigment in the image is iron, not immunolabeling. Figure 23.Macrophage proliferation, hemophagocytosis, and lymphocytic proliferation; liver, mouse implanted with an AEL PDX in which the leukemia did not engraft (mouse no. 19). (a) The liver contains mixed aggregates of macrophages (with cytoplasmic pigment) and small lymphocytes. HE. (b) The cytoplasmic pigment stains positively for iron. Prussian blue. (c) Low to moderate numbers of CD3-positive T cells are present.