As you probably already know, your blood is made up of both red and white blood cells, among other things. Your white blood cells – also known as leukocytes – are a powerful ally in keeping you fit and healthy. Here is a selection of interesting facts about these tireless little fighters:

• White blood cells only live a short life: only a few days to a few weeks.

• A drop of blood contains an average of between 7,000 and 25,000 white blood cells at a time.

• They’re produced in bone marrow as generic leucocytes and can become different types of leukocytes later on in the process.

• They act like independent single-cell organisms, able to capture invaders and wipe them out.

• There are actually five types of white blood cells. Some fight infection-causing invaders, along with outsiders like smoke and dust. Others produce antibodies, these are special proteins that help destroy foreign materials and “remember” how to make them the next time they enter your body. Some are even “alarm sounders” that control our immune response by expelling chemicals.

• Leukocytes known as T cells have a “split personality”: Some help control immune responses while others function as killer cells.

• Immune system soldiers crawl swiftly along the sides of blood vessels, moving like millipedes. Cells create tiny “legs” that attach and detach within seconds, allowing them to zip along while keeping a good grip on the vessels’ sides.

• White blood cells are able to identify proteins that indicate which cells are “you” and which are the nasty invaders. Special molecules tell them where to cross the blood vessel barrier so they can reach damaged tissue and begin to repair it.

• In bone marrow, white blood cells outnumber red blood cells 2:1. But in the bloodstream, there are about 600 red blood cells for every white blood cell. Unbelievably, white blood cells only make up 1% of our blood.

• Your own leukocytes help maintain a healthy immune system but according to the American Red Cross, they serve absolutely no purpose in donated blood.

• Our bodies can make up to 100 billion white blood cells every day, each one ready to soldier up and protect us from the things that wish to cause us harm. You can also have your white blood cell count tested to make sure you have the exact amount your body needs.