ELISA
Immunology · Biotechnology · Biochemistry
Say it: ee-LY-zuh
Short for enzyme-linked immunosorbent assay
ELISA is a lab test that uses enzyme-linked antibodies to detect and measure a specific antigen or antibody in a sample through a color change.
Also: ELISAs, enzyme immunoassay
Definition
What is ELISA?
ELISA, short for enzyme-linked immunosorbent assay, is a laboratory method for finding out whether a particular substance is present in a liquid sample such as serum, and how much of it there is. It depends on the precise binding between an antibody and its antigen. The test runs in a plastic plate with many small wells, and the molecules involved stick to the surface of each well.
In every version, one antibody carries an attached enzyme, often horseradish peroxidase or alkaline phosphatase. After unbound material is washed away, a colorless substrate is added, which the enzyme turns into a colored product; more color means more target, and a plate reader measures it as absorbance. In a direct ELISA, antigen fixed in the well is detected by a single enzyme-linked antibody. In a sandwich ELISA, a capture antibody grabs the antigen and a second, enzyme-linked antibody binds on top, making the test very sensitive. An indirect ELISA detects antibodies in a patient's blood: a known antigen in the well catches them, and an enzyme-linked antibody against human antibodies reveals them.
ELISAs are used to screen for infections such as HIV and Lyme disease, with positive results confirmed by another test, and they are a standard research tool.
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Terms that go with it
- AntibodyAn antibody is a Y-shaped protein made by B cells and plasma cells that binds tightly to one specific antigen and helps the body destroy it.
- AntigenAn antigen is any molecule the immune system can recognize as a target, especially one that prompts antibodies or T cells to respond against it.
- EnzymeAn enzyme is a biological catalyst, usually a protein, that speeds up a specific chemical reaction without being used up in the process.
- B cellA B cell is a lymphocyte, a kind of white blood cell, that produces antibodies and forms a key part of the adaptive immune system.
- BiotechnologyBiotechnology is the use of living organisms, cells or their molecules to make products or carry out processes that are useful to people.
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