Solid-phase enzyme-linked immunosorbent assay (ELISA)

Many variations of the solid-phase immunoassay are possible. Depicted in the figure is a common antigen-binding immunoassay using a primary antibody (IgE in test serum) and secondary antibody (anti-IgE). The secondary antibody is labeled, either with a radioactive or fluorescent tag or with an enzyme that can act on a substrate to generate a detectable product.