A hapten is a small molecule that can trigger an immune response in the body, but only if it is linked to a larger molecule. Thus, a hapten cannot produce an immune response on its own, but can become an antigen when bound to a protein or other macromolecule.
For example, allergens such as bee venom or house dust contain haptens. When a hapten binds to a protein in the body, a hapten-protein complex is formed, which can trigger an immune response. In this case, the body begins to produce antibodies against the hapten-protein complex, which can lead to an allergic reaction.
Haptens also play an important role in drug production. Some drugs, such as penicillin, contain haptens, which bind to bacterial proteins and cause their death. Some anticancer drugs also contain haptens, which bind to certain proteins on the surface of the tumor and cause its destruction.
In conclusion, haptens are important molecules that play a role in allergic reactions and drug production. Their ability to bind to proteins and other macromolecules makes them useful tools for the development of new drugs and therapeutic methods.