Establishment of a novel radioligand assay using eukaryotically expressed cytochrome P4502D6 for the measurement of liver kidney microsomal type 1 antibody in patients with autoimmune hepatitis and hepatitis C virus infection

J Hepatol. 1997 Jun;26(6):1396-402. doi: 10.1016/s0168-8278(97)80477-1.


Background/aims: Liver kidney microsomal type 1 antibody (LKM1) is the diagnostic marker of autoimmune hepatitis (AIH) type 2 and is also found in patients with hepatitis C virus (HCV) infection. Cytochrome P4502D6 (CYP2D6) is the documented target antigen of LKM1 in AIH, but not in HCV infection. To compare the reactivity in the two conditions, we established a radioligand assay using eukaryotically expressed CYP2D6 as target.

Methods: A 1.2-kb human CYP2D6 cDNA was isolated from a human liver cDNA library and subcloned into an in vitro transcription vector pSP64 Poly(A). Recombinant CYP2D6 was then produced by in vitro transcription/translation, metabolically labelled with 35S methionine and used in the immunoprecipitation assay. Antibodies that bound radiolabelled CYP2D6 were immunoprecipitated and their levels assessed as cpm. Sera from 50 LKM1-positive patients (26 with AIH; 24 with HCV infection), 128 LKM1-negative patients and 57 normal controls were tested.

Results: Reactivity to 35S labelled CYP2D6 was observed in all LKM1-positive sera from patients with AIH and HCV infection, but in none of the controls. The cpm in both conditions were significantly higher than in normal controls (p<0.0001), and were correlated with the immunofluorescence titres of LKM1 (r 0.87, p<0.001 and r=0.64, p<0.001 for AIH and HCV infection, respectively). Reactivity to 35S labelled CYP2D6 was inhibited by addition of an excess of eukaryotically expressed CYP2D6.

Conclusions: CYP2D6 is a major target antigen of both AIH and HCV infection. The novel radioligand assay is highly sensitive and specific.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Animals
  • Autoantibodies / blood*
  • Autoimmune Diseases / diagnosis*
  • Autoimmune Diseases / immunology
  • Biomarkers
  • Child
  • Child, Preschool
  • Cloning, Molecular
  • Cytochrome P-450 CYP2D6 / analysis
  • Cytochrome P-450 CYP2D6 / biosynthesis
  • Cytochrome P-450 CYP2D6 / immunology*
  • Hepatitis / blood
  • Hepatitis / diagnosis*
  • Hepatitis / immunology*
  • Hepatitis C / diagnosis*
  • Hepatitis C / immunology
  • Humans
  • Infant
  • Infant, Newborn
  • Kidney / enzymology
  • Liver / enzymology
  • Middle Aged
  • Radioimmunoassay
  • Radioligand Assay
  • Rats
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / immunology
  • Reference Values
  • Regression Analysis
  • Reproducibility of Results
  • Stomach / enzymology


  • Autoantibodies
  • Biomarkers
  • Recombinant Proteins
  • anti-liver kidney microsome antibody
  • Cytochrome P-450 CYP2D6