Autoimmune diseases (AIDs) are a group of diseases in which excessive and persistent autoimmune reactions lead to tissue and organ damage and cause corresponding organ lesions or clinical symptoms. Rheumatic diseases are a group of chronic diseases involving joints, cartilage, muscles and other connective tissues. Laboratory tests, especially immunological tests, are very important for the diagnosis of AID and rheumatic diseases. Only some of the commonly used tests for autoantibodies are described here. Antinuclear antibody (ANA) ANA is an autoantibody against various components of the nucleus of a cell without species or organ specificity, and can be divided into anti-DNA antibody, anti-histone antibody, anti-nucleolus antibody and antibodies against other cellular components. Together, these antibodies form the ANA spectrum. Anti-nuclear antibodies (ANA) are most commonly used to screen for systemic rheumatic diseases and autoimmune disorders.ANA tests may observe autoantibodies that react with nucleic acid and protein antigens in the cell nucleus. Antibodies that react to multiple antigens may be present in the cells. IFA can be identified only if the potency of a certain antibody is high. 1, homogenous (also called diffuse), the corresponding antigens are double-stranded DNA and histone complexes. It is common in SLE, especially in patients with kidney involvement. It can also be seen in other connective tissue diseases, such as rheumatoid arthritis, MCTD, dry syndrome, scleroderma, chronic active hepatitis and primary biliary hepatic sclerosis. 2.Peripheral (peripheral type) The corresponding antigen is double-stranded DNA, mostly seen in patients with active SLE. 3.Speckle (Speckle) is mainly antibodies against ENA, including Sm, RNP, SSA, SSB, Scl-70. It is generally believed that low potency speckle ANA is not specific to connective tissue disease and does not actually represent a clinical abnormality. Highly potent anti-Sm antibodies are mostly associated with SLE. Highly potent anti-RNP autoantibodies are seen in MCTD but also in SLE. anti-SSA and anti-SSB antibodies, seen in S.S, are also seen in SLE. when patients have anti-SSA antibodies, skin manifestations and photosensitivity are usually predominant. Scl-70 antibodies are associated with scleroderma. 4. Nucleoli (nucleolar type) The target antigen is a nucleoprotein associated with RNA molecules. It is mostly seen in scleroderma. 5.Centromere (mitotic type) Anti-mitotic antibody (ACA), mostly seen in CREST syndrome of systemic scleroderma. Commonly used detection methods are IFA, ELISA, immunoblotting, RIA, immunospot method, colloidal gold standard spot immuno-permeation method, etc.. Among them, IFA is one of the more widely used methods. Mouse liver sections or Hep-2 cells are generally used as substrate antigen slices, and when patient serum is added, the ANA in the patient serum can bind to the corresponding antigenic components in the cells. Then fluorescently labeled anti-human IgG is added, and bright green fluorescence in the cell nucleus is visible under fluorescence microscopy.