Description(s):
Antibodies to the SSA antigen (also known as Ro antigen) are one of the most frequent serological markers of autoimmunity in rheumatic diseases. They appear in 60-70% of patients with Sjögren’s syndrome (SS), 30-40% of patients with systemic lupus erythematosus (SLE), and 3-5% of patients with rheumatoid arthritis (RA). The SSA antigen is comprised of an acidic 60 kDa protein that may exist in complex with RNA (80-112 bases). However, RNA is not required for SSA antigenicity. The SSA antigen is predominantly cytoplasmic, and not located in the nucleus. Therefore, patients with antibody to SSA may be ANA negative on routine testing. Approximately 62% of ANA negative lupus patients have antibodies to SSA. Two types of anti-Ro/SSA antibodies have been identified; Ro/SSA antigens of 60 kDa and 52 kDa. Anti-SSA-60 kDa antibodies are linked to certain disorders such as SS, SLE, neonatal lupus and congenital heart block. Clinically, the presence of aSSA52 has been reported in a wide variety of diseases, includes inflammatory myositis, primary biliary cirrhosis and SS.
Principle
Autoimmune ELISA kits measure autoimmune antibodies in the serum. It is based on the principle of a solid phase enzyme-linked immunosorbent assay. The assay utilizes a specific antigen for immobilization on the microtiter wells and anti-human IgG antibody conjugated to horseradish peroxidase (HRP) for detection. The test sample is allowed to react simultaneously with the two components, resulting in autoimmune antibodies being sandwiched between the solid phase and enzyme-linked antibodies. After incubation, the wells are washed to remove unbound-labeled antibodies. A HRP substrate, TMB, is added to result in the development of a blue color. The color development is then stopped with the addition of Stop Solution changing the color to yellow. The concentration of autoimmune antibodies is directly proportional to the color intensity of the test sample. Absorbance is measured spectrophotometrically at 450 nm.
Data
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