The most crucial principle of ELISA (enzyme-linked immunosorbent assay) is a highly specific antibody-antigen interaction.
ELISA is a biochemical technique used to detect the presence of an antibody or an antigen in the biological sample. Simply described, in an ELISA, an antigen is immobilized on a solid surface and then a specific antibody is applied over the surface so that it can bind to the antigen. The antibody is usually linked to an enzyme, and in the final step, a substrate for that enzyme is added. The enzyme can convert it to some detectable signal, most commonly a color change. Medical usage of ELISA is in the diagnosis of HIV infection, pregnancy tests, measurement of cytokines…