What's the Immune System?

To be immune (say: ih-MYOON) means to be protected. So it makes sense that the body system that helps fight off sickness is called the immune system. The immune system is made up of a network of cells, tissues, and organs that work together to protect the body.

What Do White Blood Cells Do?

White blood cells, also called leukocytes (say: LOO-kuh-sytes), are part of this defense system. There are two basic types of these germ-fighting cells:

1. phagocytes (say: FAH-guh-sytes), which chew up invading germs
2. lymphocytes (say: LIM-fuh-sytes), which allow the body to remember and recognize previous invaders

Leukocytes are found in lots of places, including your spleen, an organ in your belly that filters blood and helps fight infections. Leukocytes also can be found in bone marrow, which is a thick, spongy jelly inside your bones.

How Do Vaccines Help the Immune System?

So you have this great system in place. Is it enough to keep you from getting sick? Well, everyone gets sick sometimes. But your immune system helps you get well again. And if you've had your shots (also called vaccines), your body is extra-prepared to fight off serious illnesses that your immune system alone might not handle very well. If you get the shot that covers measles, for instance, it can protect you from getting measles, if you're ever exposed to it.

How Can I Help My Immune System?

Healthy kids can help their immune systems by washing their hands regularly to prevent infections, eating nutritious foods, getting plenty of exercise, getting enough sleep, and getting regular medical checkups. And if you feel great today, thank your immune system!