Immunology

Architect is the analyzer that is used to detect the presence of antigens, Abs and analytes in the sample. The principle that it uses is the chemiluminescent microparticle immunoassay (CMIA) technology.

When the sample is loaded into the analyzer, the barcode on the plain tube will be scanned for the analyzer to conduct the respective test that was requested.

When the sample is processed, microparticles (paramagnetic microparticles coated with capture molecules) will be dispensed into the reaction vessel (RV) containing the sample (i.e.: serum). It will then be vortexed and incubated to allow the reagents and the sample to interact. If the analyte is present in the sample, it will bind to the corresponding capture molecule on the microparticles forming immune complexes. After incubation and vortexing, a magnet will attract the bound paramagnetic microparticles to one side of the surface of the RV. It will then undergo a first wash to remove unbound materials.

Next, a chemiluminescent acridinium labelled conjugate will be added into the RV. Similarly, the mixture will be vortexed and incubated. This conjugate will bind to the immune complexes. It will then undergo a second wash to remove unbound materials.

A pre-trigger solution (hydrogen peroxide) is added. It is used to acidify the environment to prevent early release of energy (i.e.: light emission) by the acridinium, it also prevents clumping of the microparticles and it will split the acridinium dye from the conjugate that is bound to the microparticle complex.

A trigger solution is added. It will cause the acridinium to be oxidized due to the presence of peroxide and alkaline solution. Oxidation of acridinium will produce N-methylacridone and release of energy (i.e.: light emission). The CMIA optical system will then measure the chemiluminescent emission to quantitate the concentration of the analyte present in the sample.

An example of a test conducted using the above principle is the Syphillis TP (Treponema pallidum). Syphillis is caused by an infection by the TP bacteria. It can be transmitted congenitally or through sexual contact. The analyzer will determine the amount (if any) of anti-TP in the patient’s serum. This will determine the diagnosis of syphilis.

Once the sample is loaded onto the analyzer, the patient’s serum, microparticles coated with recombinant TP Ag and assay diluents are aspirated and dispensed into the RV. Anti-TP present in the patient’s sample will bind to the TP Ag coated microparticle. After vortexing, incubating and washing the mixture, acridinium-labelled anti-human IgG and IgM conjugate is added. After a second vortexing, incubating and washing the mixture, the pre-trigger and trigger solutions are added to the RV. The resulting chemiluminescent reaction is measured using relative light units (RLUs). The higher the RLUs, the higher the amount of anti-TP measured.

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