STUDY OF ANTIGENIC SITES ON THE ASIALOGLYCOPROTEIN RECEPTOR RECOGNIZED BY AUTOANTIBODIES

The aim of this study was to identify the epitopes recognized by antib odies to the asialoglycoprotein receptor, a specific hepatocyte protei n, from sera of patients with autoimmune hepatitis. An ELISA test was used to detect anti-asialoglycoprotein receptor antibodies in the sera of patients with autoimmune hepatitis. Positive sera were tested agai nst the same antigen by slot blot, by Western blot and by immunoprecip itation of the untreated protein and following treatment with P-mercap toethanol (P-ME) and endoglycosidase F. The mature, unglycosylated and partially glycosylated forms of the asialogly coprotein receptor synt hesized by HepG2 cells were tested against positive patients' sera, as well as the in vitro translated unglycosylated form of the H-1 subuni t of the receptor. Sera from patients with autoimmune hepatitis recogn ized equally the native form, as well as the P-ME-modified form, but l ess well the deglycosylated form of the human mature receptor. No reac tivity was found when these sera were tested against the denatured hum an protein. In addition, neither the unglycosylated H-1 subunit nor an y of the HepG2-synthesized asialoglycoprotein receptor forms bound to the antibodies. Altogether, these results show that anti-asialoglycopr otein receptor antibodies in the sera of patients with autoimmune hepa titis are directed against conformational structures of the mature het ero-oligomeric form of the human liver protein and that at least some epitopes were located on the extracellular domain of the antigen.