Histochemical staining for β-glucuronidase activity (red) was performed on tissues from adult MPS VII mice 24 hours after injection with progenitor-derived macrophages derived from normal donors. β-Glucuronidase–positive cells assume a relatively uniform distribution in the liver (A), lung (B), and bone marrow (C). Enzyme-positive cells in the spleen are present predominantly in the red pulp, with rare positive cells observed in the germinal centers (D). In the kidney, the donor cells appear to be present primarily in the glomeruli (E). The newborn brain contains multiple β-glucuronidase–positive cells that are observed in both the meninges and the parenchyma (F). ([A], [C], [D], and [F], original magnification × 188; [B] and [E], original magnification × 300).