Anti-centromere antibodies (ACA) are an immunological marker for diagnosis of CREST syndrome, a limited form of systemic sclerosis. At least 9 proteins are known to be associated with the centromere complex, but CENP-B is normally considered to be the major centromere antigen. CENP-B has a molecular weight of approximately 66 kDa and plays an important role in the formation of the centromeric chromatin. CENP-B antibodies are present in the sera of up to 80% of patients with CREST syndrome. These autoantibodies are also often detected in sera from patients with Raynaud’s phenomenon and occasionally in other rheumatic diseases such as systemic lupus erythematosus, Sjögren’s syndrome, and rheumatoid arthritis. ACA have also been reported to occur with high prevalence in patients with primary biliary cirrhosis, in patients with malignancies and occasionally in normal individuals.
Autoimmune ELISA kits measure autoimmune antibodies in the serum. It is based on the principle of a solid phase enzyme-linked immunosorbent assay. The assay utilizes a specific antigen for immobilization on the microtiter wells and anti-human IgG antibody conjugated to horseradish peroxidase (HRP) for detection. The test sample is allowed to react simultaneously with the two components, resulting in autoimmune antibodies being sandwiched between the solid phase and enzyme-linked antibodies. After incubation, the wells are washed to remove unbound-labeled antibodies. A HRP substrate, TMB, is added to result in the development of a blue color. The color development is then stopped with the addition of Stop Solution changing the color to yellow. The concentration of autoimmune antibodies is directly proportional to the color intensity of the test sample. Absorbance is measured spectrophotometrically at 450 nm.