Which glycoprotein binds with hemoglobin to facilitate removal by the reticuloendothelial system?

Which glycoprotein binds with hemoglobin to facilitate removal by the reticuloendothelial system?

• A. Haptoglobin
• B. Ceruloplasmin
• C. Alpha1-antitrypsin
• D. Fibrinogen

Answer: (A)

Free hemoglobin released into the bloodstream is scavenged by a plasma glycoprotein called haptoglobin. It binds Hb with high affinity, forming a stable haptoglobin–hemoglobin complex. This complex is recognized and cleared by macrophages of the reticuloendothelial system (notably in the liver and spleen) via receptors such as CD163, preventing the toxic effects of free heme and conserving iron. The other proteins listed do not bind free hemoglobin in this way: ceruloplasmin carries copper and acts as a ferroxidase, alpha1-antitrypsin inhibits proteases, and fibrinogen is involved in clot formation.

Free hemoglobin released into the bloodstream is scavenged by a plasma glycoprotein called haptoglobin. It binds Hb with high affinity, forming a stable haptoglobin–hemoglobin complex. This complex is recognized and cleared by macrophages of the reticuloendothelial system (notably in the liver and spleen) via receptors such as CD163, preventing the toxic effects of free heme and conserving iron. The other proteins listed do not bind free hemoglobin in this way: ceruloplasmin carries copper and acts as a ferroxidase, alpha1-antitrypsin inhibits proteases, and fibrinogen is involved in clot formation.