Rheumatoid Factor IgG ELISA
The IMMUNOLAB Rheumatoid Factor (RF) IgG ELISA Test Kit has been designed for the the detection and the quantitative determination of RF in serum and plasma. Further applications in other body fluids are possible and can be requested from the Technical Service of IMMUNOLAB.
Rheumatoid arthritis (RA) is a chronic inflammatory disease of unknown etiology. Rheumatoid arthritis is a systemic disease characterized by chronic proliferation and inflammation of joint cartilage and supporting structures. RA is mainly defined by clinical criteria, in which systematic pathogenetic studies have been hampered by doubts about the presence of common pathogenetic mechanisms and the relative lack of unique laboratory findings. IgG rheumatoid factor has been reported to be present in sera of patients with rheumatoid arthritis both with and without IgM rheumatoid factor activity. Rheumatoid factors are IgA, IgG and IgM immunoglobulins with antibody activity directed against antigenic sites on the Fc portion of IgG molecules. Because of its pentavalent structure and ability to cross-link immunoglobulin G antigen, IgM Rheumatoid Factor is the main class identified by clinically available diagnostic assays for Rheumatoid Factor detection. Rheumatoid factors may exist as the mu, gamma, alpha, and epsilon isotypes. Rheumatoid factors are found in 1 to 4 % of the general population. They are present in 75% of adult patients with the highest incidence of rheumatoid factors occurring in persons over 65 years of age and nearly all patients with Felty and Sjogren syndrome. The clinical correlation of an elevated rheumatoid factor should be interpreted cautiously. Increased titers may accompany a variety of acute immune responses, particularly viral infections and a number of other diseases (e.g., infectious mononucleosis, tuberculosis, leprosy, various parasitic diseases, liver disease, sarcoidosis, and lymphoproliferative syndromes). The earliest tests and those still most widely used rely on the agglutinating properties of the IgM class of rheumatoid factors. Sensitized sheep red blood cell (Waaler-Rose) and latex agglutination tests have been developed and routinely employed. These assays are most sensitive for the detection of Rheumatoid factor that is of the IgM isotype because of its multivalent structure. These tests provide a dilution which is difficult to standardize and have laborious processing and poor reproducibility. In contrast to these assays modern ELISA tests are characterized by a higher sensitivity and by the possibility to differentiate between IgA, IgG and IgM Rheumatoid Factors.
The IMMUNOLAB RF IgG test kit is based on the principle of the enzyme immunoassay (EIA). Goat IgG is bound on the surface of the microtiter strips. Diluted patient serum, ready-to-use calibrators and controls are pipetted into the wells of the microtiter plate. A binding between the RF IgG of the serum and the immobilized goat IgG takes place. After a one hour incubation at room temperature, the plate is rinsed with diluted wash solution, in order to remove unbound material. Then ready-to-use anti-human-IgG peroxidase conjugate is added and incubated for 30 minutes. After a further washing step, the substrate (TMB) solution is pipetted and incubated for 20 minutes, inducing the development of a blue dye in the wells. The color development is terminated by the addition of a stop solution, which changes the color from blue to yellow. The resulting dye is measured spectrophotometrically at the wavelength of 450 nm. The concentration of the RF IgG is directly proportional to the intensity of the color.
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