Rheumatoid Factor Rheumatoid factor is an autoantibody that targets degenerate IgG and is found in the serum and joint fluid of patients with rheumatoid arthritis and certain autoimmune diseases. RF can be divided into four types: IgM, IgG, IgA and IgE. Clinical significance: 1, RF is very significant for the diagnosis of RA, with a positive rate of 60-80%. From the X-ray analysis of early RA patients, patients with persistent positive IgMRF are more likely to have bone erosion. IgMRF titers correlate with signs of RA disease activity, such as the number of joint pain and joint swelling. high IgMRF titers are a reliable and sensitive indicator of RA disease activity. Cyclic guanosine polypeptide antibody (CCP) CCP antibody is a polypeptide fragment of cyclic polysilicon. The IgG type is the predominant antibody. Clinical significance: CCP antibodies are highly specific for rheumatoid arthritis, with a positivity rate of 51% and specificity >96%, and have a strong correlation with the prognosis of rheumatoid arthritis in patients with positive rheumatoid factor. Anti-nucleosome antibodies Anti-nucleosomes are a component of the chromatin of cells that are composed of DNA and histones linked in a specific way. It has an important role in the induction and pathogenesis of SLE. Clinical significance: Anti-nucleosome antibodies appear earlier in the early stages of SLE than anti-dsDNA and anti-histone antibodies and have a higher specificity. The positivity rate is 50-90% and specificity is >98%. RA33 antibody Anti-RA33 antibody does not cross-react with other anti-extractable nuclear antigen antibodies, rheumatoid factor, anti-perinuclear factor antibody and anti-keratin antibody, which are polyclonal antibodies, mainly of IgG type. Clinical significance: RA33 antibody, in atypical early rheumatoid arthritis rheumatoid arthritis can appear, the positive rate of 27-45%, osteoarthritis, ankylosing spondylitis and psoriatic arthritis do not appear this antibody. Thus, anti-RA33 antibody is considered as one of the laboratory indicators to differentiate rheumatoid arthritis from other arthritis. a-cytosolic protein antibody a-cytosolic protein antibody is a salivary gland-specific autoantigen extracted from the lacrimal gland of a mouse model of desiccation syndrome, and the antigenic qualities are identified as a-cytosolic protein, a cleavage product of cytosolic protein. Clinical significance: a-cell lining protein antibody may play an important role in the pathogenesis of desiccation syndrome; it has significance for the diagnosis of desiccation syndrome; it may be related to the severity of the disease and prognosis of patients with desiccation syndrome.