BMT normalizes systemic heme-iron recycling and prevents pathological iron accumulation in kidneys. Perls’ stained cross-sections of paraffin-embedded tissues for nonheme iron. Areas of iron accumulation appear in blue. (A) In the spleen, heme-iron recycling macrophages loaded with iron were found throughout the red pulp of WT Ctr, were absent in untreated in KO Ctr, and were partially restored in KO BMT animals. (B) In the liver, iron-positive Kupffer cells were detected in WT Ctr animals (arrows) and were undetectable in untreated KO BMT animals but were present in large numbers in KO BMT animals (arrows). (C) In the kidneys, WT animals lacked iron accumulations, whereas the kidney KO Ctr animals had abnormal iron accumulations in proximal tubules and glomeruli. The kidneys of KO BMT animals appeared normal, consistent with restoration of normal recycling of Hb by donor macrophages in the liver and spleen. Scale bars represent 100 μm (A,C) and 50 μm (B).