Final answer:
Haptens induce an immune response only in the presence of a carrier by triggering the production of IgE antibodies that bind to mast cells and cause an allergic reaction. The correct option is D. Induce an immune response only in the presence of a carrier
Step-by-step explanation:
The primary role of haptens in the context of the immune system is to induce an immune response only in the presence of a carrier. Haptens are small molecules that cannot elicit an immune response on their own, but when they bind to a larger carrier molecule, they can trigger an immune response.
This immune response is typically mediated by the production of antibodies, specifically IgE antibodies, which can then bind to mast cells and trigger an allergic reaction.
For example, if someone is exposed to a hapten such as poison ivy oil, it can bind to a carrier protein in the skin. This creates a complex molecule that the immune system recognizes as foreign. In response, the immune system produces IgE antibodies that bind to mast cells in the skin.
Upon subsequent exposures to the hapten, the hapten-carrier complex can bind to the IgE antibodies on the mast cells, leading to the release of histamines and other mediators that cause the characteristic itching, redness, and swelling of an allergic response. The correct option is D. Induce an immune response only in the presence of a carrier