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Immune System For Kids

The immune system protects your body from pathogens that make you sick like viruses, parasites, and bacteria.

The immune system is made up of cells, organs, and tissues that team up to fight against these invaders.

Your body is exposed to millions of germs every day, and the immune system is the reason they don’t always make you sick.


When germs do make you sick, your immune system works to fight off the infection.

Your body then remembers how to fight the infection if the same germ attacks your body again.

The older you get, the more germs your body becomes protected against. This is called immunity.

White Blood Cells

White blood cells, also called leukocytes, are germ-fighting cells.

There are two types: phagocytes and lymphocytes.

Lymphocytes are divided into B cells, which grow in the bone marrow, and T cells, which grow in the thymus. B cells create antibodies that fight against specific types of germs.

T cells kill off germs by also killing off the healthy body cells that are affected.

T cells also release messengers that send signals to other cells about the invader, kind of like a police officer calling for backup.


Phagocytes attack and kill off germs without destroying body cells. Both lymphocytes and phagocytes patrol the body looking for germs to fight.

When they do find germs, these germ-fighting cells begin multiplying, and T cells send messages to other cells to do the same.

Soon, your body has a whole army fighting against the germs that can make you sick.

Problems with the Immune System

Sometimes, people have problems with the immune system that keep it from working properly.

For example, allergies happen when the immune system overreacts and thinks something harmless, like peanuts or eggs, is dangerous for your body.


Some conditions, like juvenile rheumatoid arthritis and lupus, confuse the immune system and cause it to fight good cells instead of germs.

How to Keep Your Immune System Healthy

Your immune system fights for you without any help, but there are steps you can take to make your immune system’s job easier.

Wash your hands regularly, eat healthy food, stay active, and get plenty of rest.

Sunlight can also help your immune system, and it’s important not to experience too much stress.

sunset walk

Fun Facts About the Immune System

80% of your immune system’s activity happens in the intestines.

The cells in your body are marked with a system called Human Leukocyte Antigen (HLA).

Your immune system recognizes these markings and understands that these are your cells and shouldn’t be attacked.

Vaccines introduce viruses that have already been killed or modified into the body.

Your body doesn’t know this, though, so it attacks.

Later, if you ever get the real disease, your body is more prepared to destroy it.

Your skin is your body’s first line of defense.


It has special cells that can warn the body about incoming germs, plus glands that can kill some bacteria.

Your saliva (spit) and the tears in your eyes also have special chemicals that can break down many viruses and bacteria.

Mucus in your nose, throat, and lungs traps bacteria as well, and the acid in your stomach kills most germs. Your body works hard to keep you healthy and safe!

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