Which of the following is the substance that triggers antibody production?

• A. Antigen
• B. Antibodies
• C. Aspiration
• D. Allergy

Answer: (A)

Antibody production begins when the immune system encounters a substance it recognizes as foreign, called an antigen. Antigens are any molecules or parts of molecules that the body can bind to—often features on bacteria, viruses, or toxins. When B cells meet an antigen, they become activated and many turn into plasma cells that secrete antibodies specific to that antigen. Those antibodies circulate to neutralize the invader or tag it for attack by other immune cells. The other options don’t fit because antibodies are the products of this response, not the trigger; aspiration is unrelated to immune triggering; and an allergy is a type of immune reaction to certain substances, not the general trigger for antibody production.