Anti-Gastric Parietal Cell
Enzyme-linked immunosorbent assay method for the semi-quantitative determination of specific IgG autoantibodies to GPC in human serum.
Circulating antibodies to intracellular antigens of gastric parietal cells, antibodies to intrinsic factor (type I) and antibodies to intrinsic factor B12 complex (type II) are all a common feature of pernicious anaemia (PA). Employing an indirect immunofluorescence assay, antibodies to gastric parietal cells are detected in more than 95% of patients with pernicious anaemia. Type I and II antibodies to intrinsic factor are technically difficult to detect, making anti-GPC antibodies the test of choice.
Anti-gastric parietal cell antibodies are also found in 60% of atrophic gastric and 22% of gastric ulceration cases without detectable anaemia because these conditions occur well before the onset of pernicious anaemia.
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.
The colour intensity is proportional to the amount of autoantibodies present in the original serum sample.