Understanding Haptens and Their Role in Immunoassays

Hapten is a small molecule that binds specifically to a particular antibody, and when it does so, it triggers an immune response. Haptens are typically not immunogenic on their own, but when they are linked to a carrier protein or other large molecule, they can elicit an immune response. The binding of the hapten to the antibody is called haptenation.

Haptens are commonly used in immunoassays, such as ELISAs (enzyme-linked immunosorbent assays), where they serve as the antigen being detected. In this context, the hapten is first attached to a carrier protein or other large molecule, and then added to a sample containing antibodies against the antigen of interest. If the hapten binds specifically to the antibody, it will trigger an enzymatic reaction that can be measured and quantified.

Haptens are also used in other immunological techniques such as Western blotting, radioimmunoassay (RIA) and enzyme-linked immunosorbent spot (ELISPOT) assays.