Molecular biological significance of asialoglycoprotein receptor in autoimmune hepatitis type I

应用逆转录和聚合酶链反应从人肝脏mrna中分离出asialalglyprotein receptor (ASGPR) H1和L-H2编码的cdna。利用这些cdna在大肠杆菌中表达重组ASGPR蛋白。通过免疫这些重组蛋白获得了兔抗人ASGPR H1或L-H2的特异性血清。建立了细菌重组抗原酶联免疫吸附法（ELISA）检测血清ASGPR抗体。检测了自身免疫性肝炎、原发性胆汁性肝硬化、酒精性肝病、慢性丙型肝炎、慢性乙型肝炎、系统性红斑狼疮和健康受试者的血清。重组抗原ELISA法检测的抗asgpr抗体OD值与人肝抗原ELISA法测定的抗asgpr抗体滴度存在相关性。ELISA检测ASGPR蛋白的胞外结构域，发现自身免疫性肝炎对抗ASGPR抗体的敏感性相似，而慢性丙型肝炎对ASGPR抗体的反应性较低，提示与自身免疫性肝炎抗体反应的主要表位可能位于ASGPR蛋白的胞外结构域。1例自身免疫性肝炎患者外周血单个核细胞淋巴细胞在重组ASGPR抗原淋巴细胞刺激试验中显示刺激指数为4。自身免疫性肝炎患者体内可能存在一类与人ASGPR反应的淋巴细胞。

Reverse transcription and polymerase chain reaction was applied to isolate cDNAs encoding asialoglycoprotein receptor (ASGPR) H1 and L-H2 from human liver mRNAs. Using these cDNAs, recombinant ASGPR protein was expressed in E.coli. Rabbit antisera specific to human ASGPR H1 or L-H2 was obtained by immunizing these recombinant proteins. Enzyme-linked immunosorbent assay (ELISA) using bacterial recombinant antigen was developed to measure serum antibodies to ASGPR.Sera from autoimmune hepatitis, primary biliary cirrhosis, alcoholic liver disease, chronic hepatitis C,chronic hepatitis B,systemic lupus erythematosus, and healthy subjects were tested. High OD value was obtained almost exclusively in autoimmune hepatitis and chronic hepatitis C.The OD value of anti-ASGPR antibodies detected by ELISA using recombinant antigen was correlated with anti-ASGPR antibody titers that were determined by ELISA using human liver antigen. By using extracellular domain of ASGPR protein in ELISA,similar sensitivity to pick-up anti-ASGPR antibodies was demonstrated in autoimmune hepatitis and less reactivity was detected in chronic hepatitis C.It was suggested that main epitope which was reactive with antibodies in autoimmune hepatitis could be located on the extracellular domain of the ASGPR protein. Lymphocytes from peripheral blood mononuclear cells in a patient with autoimmune hepatitis showed a stimulation index as 4 in lymphocyte stimulation test with recombinant ASGPR antigen. There could exist a certain class of lymphocytes reactive with human ASGPR in autoimmune hepatitis patients.