Liver kidney microsomal type 1 antibodies (LKM1)
A test to diagnose autoimmune hepatitis type 2.
Liver-kidney microsomal (LKM) autoantibodies are associated with Autoimmune Hepatitis type 2. This type of autoantibodies was discovered in 1973 by Rizzetto; when conducting indirect immunofluorescence test, he detected autoantibodies reacting with renal proximal tubules and cytoplasm of hepatocytes. Depending on target antigen, these antibodies are divided into 3 types, although in most if any cases, detection of basic type 1 autoantibodies is necessary and sufficient. The target antigen of LKM-1 is the microsomal cytochrome of p450 2D6 system. Type 2 and 3 antibodies are extremely rare in medically induced and viral Hepatitis; they have no independent clinical significance. Type 2 and 3 antibodies’ target antigens are also cytochromes and microsomal enzymes. The recommended practice for autoantibody detection is indirect immunofluorescence, which preserves the antigen in its native state and provides detection of all three types of antibodies.
LKM-1 antibodies are the main serological marker of autoimmune Hepatitis type 2, which predominantly affects children over 1 year of age and teenagers. Autoimmune Hepatitis type 2 is slightly more common in girls. Unlike autoimmune Hepatitis type 1, the disease is more active, more often leads to Cirrhosis, and is often accompanied by other autoimmune diseases, including Вiabetes, Vitiligo, and Autoimmune Thyreopathies. The lightning-like onset is common; the course of the disease is with periods of recrudescences and attenuation of the process; Cirrhosis often develops within 2 years. Extremely rare, LKM antibodies are detected in viral Hepatitis C (1-3%) and Hepatitis D. LKM1 antibody response can also be induced by some medicines (Tienam, Dihydralazine, Halothane, PHT, Phenobarbital, Carbamazepine). Autoantibodies to liver-kidney microsomes are rarely associated with viral Hepatitis, but interferon-alpha therapy in autoantibody seropositive patients may provoke a self-limited autoimmune disorder.
Muscle antibodies, antinuclear factor and high levels of gamma globulins are usually detected in the serum of autoimmune Hepatitis type 1 patients (chronic active Hepatitis). In type 2 autoimmune Hepatitis, LKM antibodies are detected. Finally, type 3 autoimmune Hepatitis is accompanied by the appearance of antibodies to soluble hepatic antigen. The detection of these autoimmune Hepatitis serological markers is included in the current criteria for this disease of the International Autoimmune Hepatitis Group 2008. The detection of any of these markers in high titre combined with high hypergammaglobulinaemia provides 4 of the 7 points required for a definitive diagnosis of autoimmune Hepatitis.