What are haptens?

Haptens are indeed substances that only exhibit antigenic properties when they are attached to a larger carrier molecule, commonly a protein. By themselves, haptens are too small to invoke an immune response; however, when they bind to a protein, they create a new structure that is recognized by the immune system. This complex prompts an immune response, leading to the production of antibodies specifically targeting the hapten-protein conjugate.

The ability of haptens to generate an immune response only when conjugated is crucial in immunology, particularly because it helps clarify how some small molecules can lead to allergies or other immune reactions. For example, many drug allergies can be attributed to haptens that have formed complexes with proteins in the body. This understanding underscores the role of carrier proteins in the immunogenicity of substances which, when recognized as foreign, can activate immune pathways.

Other options do not accurately define haptens. Pseudomolecules, full-sized antigens, and inorganic molecules present different mechanisms or characteristics distinct from those of haptens. Full-sized antigens, for instance, are capable of elicting an immune response by themselves without the necessity for a carrier, while inorganic molecules do not typically demonstrate the characteristic antigenicity associated with