Immunity

The human immune system is made up of several organs and tissues that work together to fight infection. Important parts include bone marrow, a spongy filling inside certain bones; the thymus, an organ in the chest; a network of vessels called lymphatic vessels; and small lumps of tissue called lymph nodes. The tonsils and spleen also play a part in immunity.

📖 In short

Immunity is your body's ability to fight the germs and viruses that cause disease. Inside you is a brave little army called the immune system, guarding your body day and night and attacking every harmful invader.

🤩 Did you know?

The British doctor Edward Jenner gave the first vaccination in 1796.
The Russian scientist Metchnikoff discovered the cells that swallow germs.
Fever is sometimes a sign that your body is fighting germs.
There are two kinds of immunity: active, which the body makes, and passive, which it gets from outside.

🔎 Find out more

🌟 The first guards

Your skin is a wall that keeps germs out, the mucus in your nose traps them, tears and saliva have substances that kill them, and stomach acid destroys many of them.

🔍 The blood's white soldiers

If a germ gets into the body, white blood cells attack it. Some swallow germs, and others make special weapons called antibodies.

💡 A strong memory

The immune system remembers germs it has fought before, so if they come back it recognizes them and destroys them quickly, before they make you ill.

🎯 Make your immunity stronger

Enough sleep, varied food with vegetables and fruit, moving and playing, keeping clean and vaccines all make your immune system strong.

📸 More pictures

The humoral immune response begins when a B lymphocyte detects an antigen. B lymphocytes are made in the bone marrow, where they mature. Each B lymphocyte responds to a particular antigen. After attaching to the antigen, the B cell divides into identical cells. Some of these mature into plasma cells, which make the antibodies that fight infection.

The cell-mediated immune response is carried out by T lymphocytes, which are made in the bone marrow and mature in the thymus. First, an antigen-presenting cell breaks the antigen into small pieces called antigenic peptides. These peptides bind to major histocompatibility complex proteins, known for short as MHC proteins, forming MHC-peptide complexes. T cell activation begins when an MHC-peptide complex binds to the T cell receptor.

🧩 Test yourself

1 Which cells fight germs in the blood?

2 What is the first barrier that keeps germs out?

3 Which picture shows “Immunity”?