The foreign particles or substances that trigger an immune response are called what?

• A. Antigen
• B. Antibody
• C. Basophil
• D. Osteoporosis

Answer: (A)

An antigen is any foreign substance that can provoke an immune response. The immune system recognizes specific features on antigens, called epitopes, and responds by producing antibodies or activating T cells to neutralize or remove the threat. Antibodies, on the other hand, are proteins made by B cells that bind to antigens to help defend the body. Basophils are white blood cells involved in allergic and inflammatory processes, not the triggers themselves. Osteoporosis is a bone-density condition, unrelated to immune triggers. So the foreign particles or substances that trigger an immune response are antigens.