ELISA
The ELISA method (Enzyme Linked Immuno-Sorbent Assay) is a technique used in biochemistry to determine if a certain substance--such as a specific cytokine or antigen--is present within a sample. It is sometimes abbreviated as "EIA."
This technique uses special antibodies that attach themselves to the substance. These antibodies generate a specific color. The amount of color indicates the amount of substance present. (Sometimes, the substance must be viewed under ultraviolet light for the antibodies to generate this color.)
Another set of antibodies are used to "capture" the substance. These antibodies adhere to both the substance and the testing container, thus holding the substance in place.
A more sophisticated and sensitive technique, the ELISPOT method, was derived from the ELISA techique.
ELISA Media
Direct ELISA diagram using a viral antigen
A sandwich ELISA. (1) Plate is coated with a capture antibody; (2) sample is added, and any antigen present binds to capture antibody; (3) detecting antibody is added, and binds to antigen; (4) enzyme-linked secondary antibody is added, and binds to detecting antibody; (5) substrate is added, and is converted by enzyme into a detectable form.
Human anti-IgG, double antibody sandwich ELISA
ELISA (Enzyme-Linked Immunosorbent Assay) plate
Schematic flowchart: ELISA and COVID-19 doi.org/10.7717/peerj.10180
