Reticuloendothelial system macrophages (RES)

The reticuloendothelial system (RES) macrophages, primarily located in the spleen, liver (Kupffer cells), and bone marrow, represent the central hub for systemic iron homeostasis (StatPearls, 2023). These cells are responsible for the phagocytosis of senescent red blood cells and the subsequent recycling of iron from hemoglobin, which is either stored as ferritin or released into the circulation via the exporter ferroportin (NIH, 2023). In clinical practice, "body iron stores" refers to the iron sequestered within these macrophages and hepatocytes, which serves as a reservoir for erythropoiesis. This system is the primary pharmacological target for iron replacement therapies, such as iron sucrose, which are processed by RES macrophages to treat iron deficiency anemia (PubMed, PMID: 22391496). Conversely, in conditions of iron overload like hemochromatosis or transfusion-dependent thalassemia, iron chelators are used to mobilize and remove iron from these storage sites to prevent organ damage (PubMed, PMID: 20630051). Dysregulation of iron handling in the RES, often driven by the hormone hepcidin, is a hallmark of the anemia of chronic disease, where iron is pathologically sequestered within macrophages (Ganz, 2013).

Other names

Mononuclear phagocyte systemMPSBody iron storesSplenic macrophagesKupffer cellsIron storage compartment

Iron replacement agents consist of iron-carbohydrate complexes that are endocytosed by macrophages of the reticuloendothelial system; the iron is then released into the intracellular iron pool to be stored as ferritin or exported via ferroportin for erythropoiesis (StatPearls, 2023). Conversely, iron chelators bind to ferric iron within these storage sites or the plasma, forming stable complexes that are excreted in the urine or feces, thereby reducing the total body iron burden (PubMed, PMID: 20630051).