In 1957 Ceppellin and Robbin et al. identified circulating DNA antibodies in the blood of patients with systemic lupus erythematosus. There are two major groups of serum anti-DNA antibodies associated with the pathogenesis and clinical manifestations of connective tissue disease. 1. anti-ds-DNA antibodies High levels of anti-ds-DNA antibodies are seen almost exclusively in SLE and are closely associated with disease activity, particularly with active lupus nephritis. Anti-double-stranded DNA antibody levels fluctuate with disease activity, with antibody levels decreasing or even turning negative during remission. Therefore, anti-double-stranded DNA antibodies can be used as an indicator of SLE activity to detect changes in SLE disease and to observe the efficacy of treatment. Since the anti-DNA antibody may turn negative or decrease in titer during the remission period of SLE, a negative result of a single measurement cannot exclude SLE. 2. Anti-SS-DNA antibody It is not only present in patients with SLE, but can also be present in other diseases that are not SLE, including inflammatory diseases, chronic active hepatitis, pharmacologic lupus, scleroderma, etc. Although it is identical to anti-ds-DNA antibodies in terms of pathogenicity, it is poorly specific and has little diagnostic value for SLE. In some SLE patients, DNA macromolecules can be present in the circulation or adherent to the microvasculature of multiple organs. All of these circulating or organ in situ DNA can react with circulating autoantibodies to form immune complexes that activate complement and lead to tissue damage.