Millions of bad bacteria and viruses surround you. Luckily, your body’s immune system has tools to destroy them. Your skin acts as your first line of defense.
Cells in your skin send a warning when germs land on it. Your skin reacts to the warning. It starts to make chemicals. T ese chemicals are germ killers. Unfortunately, germs can get past your skin.
T ey can attack through your eyes, mouth, and nose. T ese body parts fight germs, too. Imagine a cold virus attacking you, for
example. It zooms up your nostril. It quickly faces many traps inside your nose. First, it could get stuck in gooey mucus.
Next, the hairs in your nose try to sweep the virus out. Viruses don’t give up easily, though. T ey can irritate your nose. T at could make you sneeze. A sneeze could toss them out of your body.
Your body’s first lines of defense put up a good fight. Sometimes, though, germs can get past them. For instance, they might find a cut in your skin. T ey slip past your skin and into your bloodstream. T ere, they can multiply so fast that your body has a hard time fighting them off . T at’s when your white blood cells kick into
action. Millions of them fl oat in your blood. T ey’re like police officers on patrol. T ey’re looking for invaders like bacteria and viruses. T ere are diff erent kinds of white blood cells. T ey each have diff erent jobs. Here’s how your blood cells fight germs.
Let’s say you cut your finger. One group of white blood cells rushes to the scene. T ey check out the damage. T ey discover that germs have entered the cut. T e white blood cells quickly surround the germs. T ey punch holes in them and gobble them up. T is kills some germs. It damages and kills some white blood cells, too. Next, two other types of white blood cells
move in. One kind is called a B cell. T is cell is like a factory worker. It makes antibodies. Each antibody matches the germ it’s being sent to fight. It doesn’t actually kill the germ, though. It sticks to it. It’s like a sign. It tells other white blood cells that they need to come and destroy this germ. T e other kind of white blood cell is called
a T cell. T ese cells have two jobs. Some are like generals. T ey tell other cells what to do. Others are fighters. T ey hunt for the germs tagged by the antibodies. T en the T cells destroy the germs.
Your saliva and Mucus (yellow) clings to nose hairs (green). 14 NATIONAL GEOGRAPHIC EXTREME EXPLORER tears can kill germs.
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