14

CHAPTER

211

Immunity

There’s a battle going on beneath your skin. Thousands of microbes crawl into
every nook and cranny of your body in a daily invasion. Yet you rarely notice
because an army of B cells, T cells, natural killer cells, and other parts of your
immune system counterattack, ripping most microbes to pieces. Those that sur-
vive give you a runny nose, cough, and feverish feeling, and, on rare occasions,
more serious illness.
The immune system fights invading bacteria, viruses, and pollen and venom
from bees. Anything foreign that enters your body is surrounded and either
neutralized or destroyed by your immune system before it can cause damage to
your body.
In this chapter, you’ll learn the parts of the immune system and how each
functions to give you protection days and years from now.

What Is Immunity?

An immune systemis an organism’s protection from invading organisms and for-
eign substances, such as bacteria, viruses, fungi, helminths, protozoa, pollen,

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