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 antibodies to SSA may be ANA (Antinuclear Antibody) 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 Anti-SSA-52 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-mouse 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 antigen and the enzyme-linked antibodies. After incubation, the wells are washed to remove unbound antibodies. Then an HRP substrate is added to develop a blue color. The color development is 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.

Literature

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Citations

Irgm1 coordinately regulates autoimmunity and host defense at select mucosal surfaces. Azzam, Kathleen M., et al. JCI Insight, vol. 2, no. 16, 2017, doi:10.1172/jci.insight.91914.