Figures 15–17.

Histiocytosis, hemophagocytosis, and human lymphocyte engraftment; humanized NSG-SGM3 mouse (mouse no. 2). Figure 15. Spleen. (a) There is a visible distinction between the white pulp (white star) and red pulp (black star). HE. (b) The red pulp area contains numerous large macrophages with abundant cytoplasm and frequent cytoplasmic pigment. HE. Inset: the cells are immunolabeled for hNuMA1. (c) Hemophagocytosis is occasionally indicated by engulfed erythrocytes in the macrophage cytoplasm (bounded by arrowheads). HE. (d) Marked hemophagocytosis and iron accumulation (inset). Prussian blue. (e-k). Most of the macrophages are immunolabeled for hCD68 (e), with fewer being positive for hCD163 (f). The white pulp is populated by human lymphocytes, based on morphology with HE stain (g) and positive labeling for hNuMA1 (inset). The white pulp contains similar numbers of CD3-positive T cells (h) and PAX5-positive B cells (i). Most of the T cells are CD4 positive (j) with fewer CD8-positive cells (k). Figure 16. Lung. There is minimal to mild perivascular infiltration of lymphocytes and histiocytes. The histiocytes occasionally contain intracytoplasmic pigment (inset). Figure 17. Bone marrow. (a) Large histiocytes and multinucleated giant cells are scattered throughout the bone marrow, occasionally containing intracytoplasmic pigment (inset). HE. (b) The histiocytes are immunolabeled for hCD68.