Medical Laboratory Scientist (MLS) ASCP Practice Exam

A hapten is a small molecule that, when combined with a larger carrier protein, can elicit a specific immune response. In its unbound form, a hapten is typically not immunogenic on its own; it becomes immunogenic only when it is conjugated with a larger molecule, such as a protein.

In this context, proteins serve as suitable carriers because they have the ability to bind haptens and provide the necessary size and structural complexity to activate the immune system. This coupling enables the body to recognize the combination as foreign and mount an immune response, effectively transforming the hapten into an immunogenic entity.

The other choices—carbohydrates, fats, and nucleic acids—generally do not provide the same immunogenic characteristics when coupled with haptens. While they may interact with the immune system, they have not been traditionally utilized as carrier molecules in the same way proteins are for haptens. Therefore, proteins are the correct answer as they are essential for the conversion of haptens into immunogenic substances.