Enzyme immunoassays (EIAs) use the catalytic properties of enzymes to detect and quantify immunologic reactions. Enzyme-linked immunosorbent assay (ELISA) is a heterogeneous EIA technique used in clinical analyses.[1] In this type of assay, one of the reaction components is nonspecifically adsorbed or covalently bound to the surface of a solid phase, such as a microtiter well, a magnetic particle, or a plastic bead. This attachment facilitates the separation of bound and free-labeled reactant...| www.ncbi.nlm.nih.gov
The Antigen antibody interaction can be related to a lock and key mechanism. Each antibody has a unique design that fits into the shape of the antigen.| microbialnotes.com