A radioimmunoassay for detection of circulating antibodies reacting with the hepatic asialoglycoprotein receptor protein

To determine whether circulating antibodues against the liver-specific membrane lipoprotein complex (LSP), which occur in a number of liver disorders, are directed at the hepatic asialoglycoprotein receptor protein (hepatic lectin) — recently shown to be a constituent of LSP — a radioimmunoassay for anti-hepatic lectin antibodies was developed based on the use of protein A in situ on staphylococcal cells to precipitate ¹²⁵I-labelled rabbit hepatic lectin/anti-lectin immune complexes. The assay was used to test sera from 30 patients (15 anti-LSP-positive and 15 anti-LSP-negative) with autoimmune chronic active hepatitis (CAH), hepatitis B virus-positive CAH or primary biliary cirrhosis. Anti-lectin antibodies (at titres of 1 : 200 to 1 : 1600) were found in all 15 anti-LSP-positive sera and were not detected in the 15 anti-LSP-negative patients. Hepatic lectin is a highly purifiable, liver-specific, hepatocellular surface component and the anti-lectin assay (which proved sensitive, reliable and easy to perform) will permit further exploration of the role of autoimmune mechanisms in the pathogenesis of various liver diseases.