What is the enzyme-linked immunosorbent assay (ELISA) primarily used for?

The enzyme-linked immunosorbent assay (ELISA) is primarily used for testing for antibodies, including those associated with viral infections such as the AIDS virus. This immunoassay technique is highly sensitive and specific, allowing for the detection of antibodies that the body produces in response to infections. When a person is exposed to a virus like HIV, their immune system generates antibodies against it, and ELISA can quantitatively measure these antibodies in blood or plasma samples.

During this process, a sample is added to a plate coated with antigens specific to the antibodies being tested; if antibodies are present, they will bind to these antigens. The binding is then detected through an enzyme-linked secondary antibody that produces a measurable signal, often a color change, indicating the presence and quantity of the specific antibody. This characteristic makes ELISA an essential tool in diagnosing and managing infectious diseases, immunological disorders, and vaccine responses.

Other options, while relevant to laboratory practices, do not represent the primary use of ELISA. Detecting cancer markers generally involves other assays, blood glucose measurement is accomplished through different methods such as glucose oxidase assays, and separating proteins by size is usually performed using techniques like gel electrophoresis rather than ELISA.