Histopathologic analysis demonstrates no reduction in lysosomal storage in the liver (A) or spleen (F) 24 hours after injection of peritoneal macrophages. A dramatic decrease in lysosomal storage is observed in the liver 7 (B), 15 (C), and 30 (D) days after injection. A similar reduction in storage is observed in the spleen 7 (G), 15 (H), and 30 (I) days after injection. Progenitor-derived macrophages provide an equivalent level of correction. The histopathological appearance of the liver (E) and spleen (J) from an untreated age-matched MPS VII mouse is shown. (Original magnification × 242.)