The immune system

The immune system: Your body’s frontline defender

The immune system — which is a complex network of glands, tissues, and circulating cells — is your body’s frontline defense in the fight against infection by viruses, bacteria, and other bad guys. When confronted with an infection, the immune system gears up to neutralize the foreign invader and make you healthy again.

In order for your immune system to do its job properly, it has to be able to distinguish between the good guys (the cells, tissues, and organs that make up your body) and the bad guys (any foreign invader, such as a virus or bacteria that doesn’t share your genes). And get this: The immune system is so powerful that it would reject a pregnant woman’s developing fetus (which shares only some of her genes) if the hormones of pregnancy didn’t suppress her immune system.

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