Liver/kidney microsomal antibody type 1 and liver cytosolantibody type 1 concentrations in type 2 autoimmune hepatitis

Background—Liver/kidney microsomal antibody type 1 (LKM1) and liver cytosol antibody type 1 (LC1) are the serologicalmarkers of type 2 autoimmune hepatitis (AIH).
Aims—Since LKM1 and LC1 react against two distinctliver specific autoantigens (cytochrome P450IID6 (CYP2D6) and a 58 kDa cytosolic polypeptide respectively), the aim was to see whether LKM1and LC1 concentrations correlate with liver disease activity.
Patients—Twenty one patients with type 2 AIH were studied.
Methods—All sera were tested by indirectimmunofluorescence, counterimmunoelectrophoresis, and immunoblottingvisualised by enhanced chemiluminescence. To evaluate LKM1 and LC1levels, the 50 kDa microsomal reactivity (corresponding to CYP2D6) andthe 58 kDa cytosolic reactivity were quantified by densitometric analysis.
Results—Seven patients were positive for LKM1,nine for LC1, and five for both. Serial serum samples at onset andduring immunosuppressive treatment were analysed in 13 patients (fourpositive for LKM1, six positive for LC1 and three positive for both).During remission, LKM1 concentration remained essentially unchanged insix of seven patients, and decreased in only one. Conversely, in two ofnine patients, LC1 was completely lost, and, in the remaining seven, LC1 concentration was reduced by more than 50%. Afterimmunosuppression tapering or withdrawal, flare ups of liver necrosisensued with increasing LC1 concentration, but not LKM1.
Conclusions—LC1 concentration, at variance withthat of LKM1, parallels liver disease activity, and its participationin the pathogenic mechanisms of liver injury can be hypothesised.