Immune system
The body's defence against pathogens, based mostly on white blood cells.
Last updated
Analogy
An army with scouts, soldiers and a memory of past enemies.
In practice
After you catch chickenpox once, your body remembers it and usually fights it off quickly next time.
Practice
Flashcards
- What do white blood cells do?Engulf pathogens, make antibodies and make antitoxins.
Interview questions
- Explain how a vaccine gives protection against a disease.
- A vaccine contains a dead or weakened pathogen or its antigens
- White blood cells make antibodies against the antigens
- Memory cells stay in the body
- A later infection is destroyed quickly before symptoms develop
Questions people ask
What are the three ways white blood cells attack pathogens?
Phagocytes engulf pathogens and digest them. Lymphocytes make antibodies that stick to antigens on pathogens and mark them for destruction. Some lymphocytes also make antitoxins, which cancel out poisons released by bacteria. Together these three actions clear the infection from the body.
Why do you get a fever when you are ill?
A higher body temperature makes it harder for many pathogens to multiply and helps white blood cells work faster. The brain raises the body's temperature set point when it detects infection. A mild fever is a normal defence, though a very high one needs medical care.