antigens

Antigens are molecules or parts of substances, like bacteria, viruses, or toxins, that your immune system recognizes as foreign or harmful. When an antigen enters your body, it triggers an immune response, prompting various immune cells to activate and fight off the invader. Think of antigens as unique identifying markers on the surface of these invaders—they help your immune system distinguish between harmless substances and actual threats. This recognition process is essential for protecting your body from infections and for developing immunity, as your immune system can remember these antigens to respond faster if the same invader appears again.