White Blood Cell

immune system · body defense · microscopic

Tiny body guards. White blood cells are part of your immune system and are larger than red blood cells. They travel through your blood looking for harmful germs and invaders that could make you sick.

Three main types. There are three main groups of white blood cells: granulocytes (which grab and destroy germs), lymphocytes (which remember past invaders), and monocytes (which are large cleanup crew members).

Attack the bad guys. When white blood cells find a dangerous bacterium or virus, they can surround it and destroy it before it harms your body. This is how your body fights off infections like colds and flu.

Always on patrol. Your bone marrow is constantly making billions of new white blood cells to replace the ones that get used up fighting germs. Your body is basically a never-ending factory of defenders.