Anti-dsDNA
Enzyme-linked immunosorbent assay method for the quantitative determination of specific IgG autoantibodies to dsDNA in human serum.
Anti-double-stranded (ds) DNA antibodies are found along with a wide variety of antibodies recognising other nuclear components in Systemic Lupus Erythematosus (SLE). SLE is a disease of unknown aetiology, being characterised by widespread organ involvement including renal, CNS and skin as well as joint disease. Anti-dsDNA antibodies have been suggested to be directly involved in the disease process, being included in the ARA criteria for the diagnosis of the disease. This involvement is thought to be due to either dsDNA-anti-dsDNA complexes which have been detected in some patients or to the cross-reaction of anti-dsDNA antibodies with other molecules such as the phospholipids or glycosaminoglycans of connective tissues and cell surfaces. In SLE patients, levels of anti-dsDNA antibodies can be used in the monitoring of disease activity, since rapid increases have been reported to precede exacerbation of the disease and falls in antibody levels often accompany drug therapy. Anti-dsDNA antibodies are not detected in the sera of patients with drug-induced lupus.
The Autostattm II assay for detection of autoantibodies is a solid phase immunosorbent assay (ELISA) in which the analyte is indicated by a colour reaction of an enzyme and substrate. The Autostattm II wells are coated with purified antigen.
On adding diluted serum to the wells the antibodies present bind to the antigen. After incubating at room temperature and washing away unbound material, horseradish peroxidase conjugated anti-IgG monoclonal antibody is added, which binds to the immobilised antibodies.
Following further incubation and washing, tetra-methyl benzidine substrate (TMB) is added to each well. The presence of the antigen-antibody-conjugate complex turns the substrate to a dark blue colour. Addition of the stop solution turns the colour to yellow. The colour intensity is proportional to the amount of autoantibodies present in the original serum sample.