The body reacts to the injection of a vaccine by producing ____________.

• A. Hormones
• B. Antigens
• C. Antibodies
• D. Enzymes

Answer: (C)

Vaccines introduce a harmless piece of a pathogen that the immune system can recognize. In response, B cells activate and produce antibodies—proteins that bind specifically to that pathogen. These antibodies neutralize the invader and mark it for attack, and memory B cells remain to provide a faster, stronger response if the real pathogen is encountered later. Hormones regulate body processes and aren’t produced as the primary defense to a vaccine. Antigens are the substances that trigger the immune response, not what the body makes in reaction to vaccination. Enzymes are metabolic catalysts and aren’t produced as the direct outcome of a vaccine exposure.