ELISA is a test used in immunology and medicine to detect antibodies and antigens. It uses enzyme-linked antibodies to determine results and has replaced radioactive tests. The most common type is indirect ELISA, used to detect antibodies against infectious diseases. The test involves adding a sample to a microtiter plate coated with a specific antigenic protein and using a secondary detection antibody labeled with an enzyme to cause a color change if the test is positive. The sandwich ELISA is used to detect antigens in a sample.
The ELISA method is a test used in immunology and other scientific fields to detect antibodies and antigens. ELISA stands for enzyme-linked immunosorbent assay, which refers to the fact that enzyme-linked antibodies are used to determine test results. The ELISA method is used in medicine to detect antibodies to disease as a diagnostic measure and is a common technique used in immunological and biochemical research.
The ELISA test was developed in the 1960s and 1970s as a replacement for immunological tests that involved the use of radioactive antibodies and antigens. The risks of using radioactive materials have made the testing process complicated and dangerous, and the advent of the ELISA method has solved both of these problems. Instead of using radioactive materials to determine the results of a test, ELISA uses enzymes that react with antibodies to form colored products. Color development in an ELISA test indicates a positive result.
There are several types of ELISA tests. The most commonly used ELISA method is called indirect ELISA; this is an antibody test used to determine if a certain type of antibody is present in a sample and at what concentration. In diagnostic medicine, this test is used to detect the presence of antibodies against infectious diseases such as HIV, hepatitis and others. The presence of antibodies to these diseases indicates that the individual being tested has been exposed to infectious agents. Typically, the sample used is a patient’s blood.
In this test, a specific antigenic protein is used to coat a microtiter plate. This small plastic plate contains 96 tiny wells and a single ELISA test can be run in each well. The antigen used for a given test depends on the type of antibody the test is trying to detect. For example, if ELISA is used for an HIV test, the antigen used would be specific for this virus.
As the test progresses, small amounts of the unknown sample are added to each well of the microtiter plate and the plate is incubated to allow the antibodies in the sample to bind to the antigen. Subsequently, a secondary detection antibody is added to each well of the plate. If the sample contains any of the type of antibody being tested, it will bind to the secondary detection antibody during the subsequent incubation period.
The key to the ELISA method is that the secondary antibody is labeled with a particular type of enzyme. The enzyme used is able to change the color of the sample under examination when it reacts with its substrate. Therefore, if a sample contains one of the test antibodies, adding the substrate to a well will cause the substrate to change color, due to the presence of the secondary antibody and its associated enzyme.
There are other variations of the ELISA method, including a test called the sandwich ELISA. This is used to detect antigens in a sample, rather than antibodies. In this test, the microwell plate is coated with a standardized sample of antibody. Next, the antigen test sample is added, followed by the addition of the secondary detection antibody and its associated enzyme. As with indirect ELISA, the formation of a colored product indicates a positive result.
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