ELISA is the abbreviation for Enzyme-Linked Immuno Sorbent Assay.
The principle is the binding of a labeled specific antibody to the target antigen (called analyte). The signal of the enzyme labeled antibody is the conversion of a substrate, which can be detected and quantified.
The most important assay formats are:
Typical format in virology or allergy diagnostics e.g. for detection of specific IgG, IgE or IgM in human serum. This assay format is also known as Antigen-Down format.