In the current issue of the journal (see page 553), Muratoriet al provide convincing evidence that cytochrome P4502D6 (CYP2D6) is present on the liver cell plasma membrane. This finding has important implications because CYP2D6 is the main target of liver kidney microsomal antibody type 1 (LKM1). Not only is LKM1 the serological hallmark of autoimmune hepatitis type 2 but it is also found in up to 10% of patients with chronic hepatitis C virus (HCV) infection where it appears to single out patients experiencing serious side effects while receiving interferon treatment.1

The issue as to whether CYP2D6 is present on the plasma membrane was critically reviewed in 19932 but was not resolved in view of the contrasting evidence at the time. Muratoriet al have settled this matter by incubating LKM1 containing sera with live hepatocytes …