Human Anti-dsDNA IgG ELISA Kit

Anti-DNA antibodies include anti-double-stranded DNA (dsDNA) and anti-single-stranded DNA (ssDNA) antibodies. Anti-ssDNA antibodies can occur in many diseases and are therefore of no practical value in clinical practice. In 1967, Arana discovered an autoantibody that could bind to natural DNA (nDNA) in the serum of patients with systemic lupus erythematosus (SLE), called anti-natural DNA antibodies or anti-double-stranded DNA antibodies. Subsequent studies have shown that anti-dsDNA antibodies are present almost exclusively in the serum of SLE patients and are a marker antibody for SLE. Anti-dsDNA is closely associated with the onset, pathological changes and prognosis of SLE. Anti-dsDNA antibodies bind to the deoxyribose phosphate backbone of DNA (the peripheral region) to form immune complexes. They can remain in the circulation or be deposited in local tissues, causing inflammatory damage by activating complement and playing an important role in the pathogenesis of systemic lupus erythematosus. There are two subtypes: IgG and IgM.

Figure 1. The pathogenic mechanism of anti-dsDNA antibodies in LN. (Sources: Wang X, et al. 2019)

Methods for determining this antibody include indirect immunofluorescence (IIF), radioimmunoassay, ELISA, haemagglutination, etc. IIF has the advantage of high sensitivity and specificity. It uses Trypanosoma equina or C. versicolor as substrates and exploits the biological characteristics of pure double-stranded DNA kinetochores in their bodies to perform immunofluorescence assays. Those with a serum dilution of 1:5 or higher can be diagnosed as positive. The titer of normal individuals is less than 1:5. It can be used for screening tests against dsDNA. When performing a radioimmunoassay, it is important to select the DNA antigen, which must be dsDNA. The ELISA must coat the DNA on an enzyme-labelled plate. ssDNA is easy to coat directly, whereas dsDNA must be coated with a medium such as polylysine, fish arginine or methylated bovine serum albumin. There is no comparability between different detection methods because the sources of DNA antigens are different, the antigen states are different, the reaction conditions are different, and the sensitivity and affinity of antibodies of different methods are different.

Anti-double-stranded DNA antibodies have a high specificity for diagnosing SLE, with a specificity of 90% to 95%. They are specific indicators of SLE. They rarely occur in other diseases or normal people and are parallel to the activity of the disease. As the disease activity is controlled, the antibody titer can decrease or disappear. Some scholars believe that once anti-dsDNA antibodies are detected in normal people, 80% to 90% will eventually develop into SLE within 5 years. Anti-double-stranded DNA antibodies combine with DNA to form immune complexes that are deposited on the glomerular basement membrane, or they directly act on glomerular antigens to cause renal damage in SLE patients. Therefore, anti-double-stranded DNA antibodies are closely related to lupus nephritis (LN). The titer of anti-dsDNA rises and falls with the activity of the disease. In patients with improved condition, the titer often decreases or even turns negative. Therefore, negative anti-dsDNA antibodies cannot rule out systemic lupus erythematosus. Its detection rate and titer depend on the activity of the disease. Different subtypes of anti-dsDNA antibodies are associated with different clinical phenotypes of SLE. IgM anti-dsDNA antibodies may be related to SLE skin lesions, and IgG antibodies are related to the occurrence of SLE nephropathy. Some scholars believe that the ratio of IgG/IgM subtype antibodies can be used as one of the predictive indicators of SLE nephropathy. Data show that those with positive anti-dsDNA antibodies have more proteinuria, hematuria, progressive renal function deterioration, and repeated attacks of LN than those with negative anti-dsDNA antibodies, which is statistically significant. Patients with positive anti-dsDNA antibodies have a 12-fold higher risk of nephritis than those with negative anti-dsDNA antibodies. Therefore, it is shown that those with positive anti-dsDNA antibodies, especially those with persistent high titers, often have renal damage. At the same time, the latest research also believes that the increase in anti-dsDNA antibody titers is related to the activity of LN and is one of the independent risk factors for LN. The results showed that the positive rate of anti-dsDNA antibodies in the LN group was 65.22%, significantly higher than the 51.67% in the SLE group without nephritis; the titer of anti-dsDNA antibodies in the group without nephritis was mostly low, while the high titer of antibodies in the LN group, 1:320 accounted for 26.67%, and 1:1000 accounted for 9.33, which was significantly higher than that in the group without nephritis. These are consistent with the latest research, indicating that anti-dsDNA antibody detection can be used as an important indicator for the diagnosis and efficacy observation of LN. And when the anti-dsDNA antibody titer is high (1:320, 1:1000), the corresponding ANA titer is also very different between the LN group and the group without nephritis. The high titer results of ANA in the LN group accounted for the majority, while the high, medium and low ANA titer results in the group without nephritis were more evenly distributed, and the difference between the two groups was statistically significant. This shows that the combined detection and analysis of anti-dsDNA antibodies and ANA is more meaningful for the diagnosis of LN.

Duplex DNA
ds-DNA
Double Helix DNA
dsDNA Molecule
Double-Stranded Deoxyribonucleic Acid
Double-Stranded Nucleic Acid