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A human cytochrome P-450 is recognized by anti-liver/kidney microsome antibodies in autoimmune chronic hepatitis
L Kiffel1, J Loeper, J C Homberg
1INSERM U 75, CHU Necker-Enfants Malades, Paris.
Abstract:
1- Anti-liver/kidney microsome autoantibodies type 1 (anti-LKM1), observed in some children with chronic active hepatitis, were used to isolate their antigen in human liver microsomes. A protein, called P-LKM1 was thus purified. This protein was recognized by a rabbit antiserum directed against the related human cytochromes P-450 bufI and P-450 bufII. 2- A human liver microsomal protein immunoprecipitated with anti-LKM1 sera was also recognized by anti cytochromes P-450 bufI/II antibodies. 3- Anti-LKM1 antibodies potently inhibited microsomal bufuralol 1'-hydroxylation. These results displayed the possible identity between cytochrome P-450 bufI/II and LKM1 antigen.
Insights
Researchers identified a protein, P-LKM1, recognized by anti-liver/kidney microsome autoantibodies type 1 (anti-LKM1). This protein is likely cytochrome P-450 bufI/II, crucial in chronic active hepatitis.
Area of Science:
- Hepatology
- Immunology
- Biochemistry
Background:
- Autoimmune liver diseases, such as chronic active hepatitis, can be associated with specific autoantibodies.
- Anti-liver/kidney microsome autoantibodies type 1 (anti-LKM1) are markers found in some pediatric cases of chronic active hepatitis.
- Understanding the target antigens of these autoantibodies is crucial for diagnosing and understanding the pathogenesis of autoimmune liver diseases.
Purpose of the Study:
- To isolate and identify the antigen recognized by anti-LKM1 antibodies in human liver microsomes.
- To investigate the relationship between the anti-LKM1 antigen and cytochrome P-450 enzymes.
Main Methods:
- Purification of a protein (P-LKM1) from human liver microsomes using anti-LKM1 autoantibodies.
- Characterization of the purified protein using rabbit antiserum against human cytochromes P-450 bufI and P-450 bufII.
- Immunoprecipitation assays to confirm the reactivity of the P-LKM1 antigen with both anti-LKM1 sera and anti-cytochrome P-450 bufI/II antibodies.
- Enzyme activity assays to assess the effect of anti-LKM1 antibodies on microsomal bufuralol 1'-hydroxylation.
Main Results:
- A specific protein, designated P-LKM1, was successfully purified from human liver microsomes.
- The purified P-LKM1 protein was recognized by a rabbit antiserum against human cytochromes P-450 bufI and P-450 bufII.
- Immunoprecipitation confirmed that the human liver microsomal protein targeted by anti-LKM1 sera is also recognized by antibodies against cytochromes P-450 bufI/II.
- Anti-LKM1 antibodies demonstrated potent inhibition of microsomal bufuralol 1'-hydroxylation, an activity mediated by cytochrome P-450 enzymes.
Conclusions:
- The results strongly suggest that the LKM1 antigen is identical to cytochrome P-450 bufI/II.
- This identification provides a molecular basis for anti-LKM1 autoantibody production in chronic active hepatitis.
- The findings contribute to the understanding of autoimmune responses targeting specific cytochrome P-450 enzymes in liver disease.