Anti-Jo-1
Enzyme-linked immunosorbent assay method for the semi-quantitative determination of specific IgG autoantibodies to Jo-1 in human serum.
The detection of Anti-Nuclear Antibodies (ANAs) has long been an important tool in the diagnosis of systemic rheumatic diseases. The antigens used in their detection are purified by the saline extraction of human or animal nuclei, this has led to them being termed Extractable Nuclear Antigens (ENAs). The most commonly measured ENA specifications are anti-SS-A/Ro, anti-SS-B/La, anti-Sm, anti-Sm/RNP, anti-Jo-1 and anti-Scl-70.
The ENA Jo-1 is a target for immune response in many patients with polymyositis and dermatomyositis and the antibodies to Jo-1 are considered markers for these conditions. In polymyositis the striated muscle becomes inflamed and the muscle fibre is degraded. When this condition exists along with typical skin changes, it is known as dermatomyositis. Approximately 25% of patients with these conditions will display higher levels of Jo-1 antibodies. Jo-1 antibodies are also associated with pulmonary fibrosis and Raynaud’s disease. The Jo-1 antigen has been identified as the enzyme histidyl-tRNA-synthetase
The AutostatII assay for detection of autoantibodies is a solid phase immunosorbent assay (ELISA) in which the analyte is indicated by a colour reaction of an enzyme and substrate. The AutostatII wells are coated with purified antigen (1).
On adding diluted serum to the wells the antibodies (2) present bind to the antigen. After incubating at room temperature and washing away unbound material, horseradish peroxidase conjugated anti-IgG monoclonal antibody (3) is added, which binds to the immobilised antibodies.
Following further incubation and washing, tetra-methyl benzidine substrate (TMB) (4) is added to each well. The presence of the antigen-antibody-conjugate complex turns the substrate to a dark blue colour. Addition of the stop solution turns the colour to yellow.