True or False: A hapten can elicit an immune response by itself.

A hapten is a small molecule that, on its own, cannot provoke an immune response. It lacks the molecular size and complexity required to be recognized by the immune system as a threat. However, when a hapten binds to a larger carrier protein, it can form a new structure that can be recognized by immune cells, allowing the immune system to respond.

This characteristic of haptens emphasizes their need for a larger molecule to generate an immune response. The immune system typically reacts to large, complex molecules, such as proteins, which contain multiple epitopes that can be recognized by antibodies. When haptens become attached to larger molecules, they can create new epitopes that the immune system can recognize.

Understanding this aspect of haptens is crucial in contexts such as allergy development and the creation of some vaccines where these small molecules play a role only when conjugated to larger proteins.