Anti-ssDNA
Enzyme-linked immunosorbent assay method for the quantitative determination of specific IgG autoantibodies to ssDNA in human serum.
Anti-single stranded (ss) DNA antibodies are found in a selection of connective tissue diseases. Anti-ssDNA antibodies are found along with several other antibodies recognizing nuclear components in drug-induced Lupus Erythematosus. The presence of anti-ssDNA antibodies can be an indication of general autoimmune dysfunction.
Anti-ssDNA antibodies are found in approximately 60% of patients with Systemic Lupus Erythematosus (SLE), 10 – 20% of patients with Mixed Connective Tissue Disease (MCTD), 10 – 30 % of patients with Primary Sjögren’s Syndrome (SS), 10 – 20 % of patients with Progressive Systemic Sclerosis/Scleroderma, 10 – 20 % of patients with Dermatomyositis/Polymyositis (DM/PM) and 35 – 40 % of Rheumatoid Arthritis patients. Antibodies to ssDNA are also associated with pre-eclampsia in pregnant women and can be found in up to 40 % of pre-eclampsia cases. There is also a high occurrence of anti-ssDNA in Antinuclear Antibody (ANA) positive type 1 autoimmune hepatitis with the antibodies found in approximately 85 % of cases.
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.