Description
Intended Uses: This ELISA is a solid phase enzyme immunoassay employing human recombinant SLA/LP for the quantitative and qualitative detection of IgG antibodies against soluble liver antigen (SLA) in human serum.
Principle of the Assay: Serum samples diluted 1:101 are incubated in the microplates coated with the specific antigen. The antibodies, if present in the specimen, bind to the antigen. The unbound fraction is washed off in the following step. Afterwards anti-human immunoglobulins conjugated to horseradish peroxidase (conjugate) are incubated and react with the antigen-antibody complex of the samples in the microplates. Unbound conjugate is washed off in the following step. Addition of TMB-substrate generates an enzymatic colorimetric (blue) reaction, which is stopped by diluted acid (color changes to yellow). The intensity of color formation from the chromogen is a function of the amount of conjugate bound to the antigen-antibody complex and this is proportional to the initial concentration of the respective antibodies in the sample.
Background: Autoimmune hepatitis (AIH) is a chronic progressive liver disease of unknown origin that responds well to immunosuppressive therapy, but has a poor prognosis if untreated. Early and accurate diagnosis is therefore of great importance. AIH is characterized by histological features of periportal hepatitis in the absense of viral markers, by hypergammaglobulinemia and, in the majority of individuals, by the presence of autoantibodies in serum. 70% of all individuals have significant titres of anti-nuclear antibodies (ANA), smooth-muscle autoantibodies (SMA) or liver-kidney microsomal autoantibodies (LKM). These antibodies are of significant value for AIH but not specific for the disease since they also occur in 10-15% of individuals with viral hepatitis and other immune-mediated diseases. In contrast, antibodies to soluble liver antigen (SLA) and antibodies to a liver and pancreas antigen (LP) are the only to be specific for autoimmune hepatitis and are present in 20% of all AIH-individuals, many of whom are negative for other autoantibodies. It was shown that anti-SLA and anti-LP are directed against the same antigen and thus are identical. The SLA/LP antigen cloned and sequenced in 2000 is a protein of unknown function, suggested to be an UGA-suppressor tRNA-associated protein