A Level Biology Practice Exam

Which term refers to a chemical that triggers an immune response?

1. Antibody

2. Antigen

3. Antitoxin

4. Antibiotic

The correct answer is: Antigen

The term that refers to a chemical that triggers an immune response is indeed antigen. Antigens are substances that are recognized by the immune system as foreign, prompting the body to produce an immune response. This response often involves the production of antibodies, which are specific proteins that bind to the antigens and help neutralize or eliminate them. Antigens can be found on the surface of pathogens such as bacteria and viruses, as well as in other foreign substances. When the immune system detects an antigen, it recognizes it as a potential threat, which leads to the activation of various immune cells. This process is crucial for the body’s defense against infections and diseases. In contrast, antibodies are created by the immune system in response to antigens, while antitoxins specifically neutralize toxins produced by certain pathogens. Antibiotics are medications used to treat bacterial infections but do not directly trigger an immune response.