Detection of circulating autoantibodies directed against the asialoglycoprotein receptor using recombinant receptor subunit H1

Abstract

Background/aims: The asialoglycoprotein-receptor (ASGPR) is a major liver-specific target autoantigen in autoimmune hepatitis. ASGPR heteromers of two subunits H1 and H2 provide clearance of circulating asialoglycoproteins by receptor-mediated endocytosis. The aim of this study was to establish whether a recombinantly expressed subunit H1 presenting conformational epitopes is capable of detecting autoantibodies against ASGPR in patients with inflammatory liver disease.

Methods: The major subunit H1 was expressed in human-embryo-kidney 293-cells and prepared by ligand-affinity-chromatography similar to the complete receptor from normal liver. Reactivities of anti-ASGPR positive sera from 219 patients with both recombinant H1 and natural receptor were compared using enzyme-immunoassay (EIA).

Results: 194 of 219 sera (88.6%) showed absorbance values on 293-H1 within a range of +/-15% compared to the natural receptor. 145 of 149 sera (97.3%) positive on ASGPR were also positive on recombinant H1. Titers of 61/62 sera (98.4%) revealed no deviation of more than one dilution step. ASGPR reactivity could be inhibited in 29 sera with up to 50 ng/microl of 293-H1.

Conclusions: These results indicate that the antigenic sites of the human ASGPR are mainly located on the mammalian-expressed subunit H1. Therefore, 293-H1 is a powerful tool for the detection of autoantibodies against ASGPR.