The asialoglycoprotein receptor was first characterized in 1968 by [https://www.sciencedirect.com/science/article/pii/S0021925818993373?via%3Dihub Morell et al.] and was the first mammalian lectin identified. The researchers transferred radioactively-labeled ceruloplasmin that had undergone a reaction via the enzyme neuraminidase to remove the protein's terminal sialic acid, generating an asialoglycoprotein. Upon injection of the radioactive protein into rabbits, the radioactivity of the entire asialoglycoprotein (rather than a portion of the protein) quickly moved from the blood into the liver. This rapid movement from the blood into the liver only occurred if the sialic acid of the protein was removed; i.e., if the protein had an exposed galactose residue (that would normally be covered by the sialic acid). Thus, it was concluded that a receptor is capable of recognizing asialoglycoproteins (i.e., proteins that have lost their terminal sialic acids) and removing them from circulation by transporting them to the liver.