Radioimmunoassay and Enzyme-Linked Immunosorbent Assay

In this article the principle of immune system and the history of the immunoassays until invention of two key techniques namely radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) are thoroughly reviewed. The article also covers the antibody production and different classes of antibodies while it also describes different types of antigens and the specific interactions between the two biomolecular entities. Side chain theory by Paul Ehrlich has established our first understandings of the specific interaction between the antibodies and the antigens. Further development of our knowledge has proven that various factors play significant roles in this interaction. Nevertheless, the principles of all immunoassays relied upon this key phenomenon: the coupling of an antigen with an antibody in a unique manner. This has laid the foundation of labeling strategies for conducting immunoassays. Radioactive substances were one of the primary labels used in immunoassay. Despite their popularity, they posed potential health threat to those exposed to the radiolabeled biomolecule. The article reviews the raise and the fall of RIA, which later was replaced by ELISA; the technique that even to date remains the gold-standard immunoassay and has various applications in different fields.