- For the artificial intelligence program, see ELIZA
The Enzyme-Linked Immunosorbent Assay (ELISA or EIA for short) is a method usually employed in biochemistry to detect if a certain substance is present in a sample. It utilizes antibodies specific to the substance; these antibodies are linked to an enzyme which causes a chromogenic substrate to produce a signal.
The steps of the general ELISA test are:
- Apply the sample to some sticky substrate, usually a plate with wells.
- Apply the enzyme-linked antibodies and let them bind to the substance.
- Wash the plate, so that unbound antibodies are removed.
- Apply a chemical which is converted by the enzyme into a fluorescent signal.
- View the result: if it fluoresces, then the sample contained the substance.
The enzyme acts as an amplifier: even if only few enzyme-linked antibodies are present, the enzyme molecules will produce many fluorescent signal molecules.
A variant of this technique is used in medicine to detect if a person's blood contains antibodies against a certain antigen (which would indicate past or present infection). The initial screening test for HIV infection is such an ELISA test. The steps are as follows:
- Prepare a plate to which the antigen is bound
- Apply the human serum to be tested
- Wash the plate, so that unbound antibodies are removed.
- Apply the enzyme-linked antibodies which specifically bind to the human antibodies.
- Wash the plate, so that unbound enzyme-linked antibodies are removed.
- Apply a chemical which is converted by the enzyme into a fluorescent signal.
- View the result: if it fluoresces, then the serum sample contained antibodies against the antigen.
See also:
External links