The Immune System (textbook)

The immune system is the body's defense network that protects against infections and illnesses. It detects harmful invaders like bacteria, viruses, and fungi, and activates various cells and molecules to neutralize or destroy them. Key components include white blood cells, antibodies, and organs like the lymph nodes and spleen. The immune system also remembers past invaders, enabling faster responses if re-exposed. It maintains a delicate balance—overactivity can cause allergies or autoimmune diseases, while underactivity may lead to frequent infections. Overall, it works continuously to keep the body healthy by identifying and eliminating threats.