How does the immune system work?

Every day your marrow makes about 100 billion new defenders. Immune cells are born in the red bone marrow, T cells are trained in the thymus, and they gather in about 600 lymph nodes, the tonsils, the spleen and the gut's Peyer's patches.

Read how it works: How does the immune system work? · The history of the immune system · More boxes on Glassbox

Chapters in this interactive model

1. An army spread through your body: Lymph vessels and nodes, the thymus, spleen, tonsils and bone marrow.
2. Walls, fire and hungry cells: Skin, mucus and acid keep germs out. When one gets in, inflammation and eater cells hit back in minutes.
3. Learning the enemy: T cells and B cells learn one germ’s exact shape and build weapons made for it.
4. Memory, and training without the danger: Why you rarely get measles twice, how a vaccine teaches the same lesson safely, and how a crowd protects the few who can’t be vaccinated.
5. The body’s drain and filter: Fluid leaks out of your blood all day. Lymph vessels collect it, filter it through the nodes and pour it back.
6. When defences misfire, and how to help them: Allergies, autoimmunity, HIV, antibiotic resistance, and the habits that keep your army strong.