Immune System Facts

Your Home Defense

Your immune system is your body's version of the military: sworn to defend against all who threaten it, both foreign and domestic. It has some really interesting soldiers that help make this possible.

When functioning properly, your immune system protects against disease, infection, and helps you recover after an injury. Then again, like everything, something can go wrong and change the entire game.

Read on to learn more about the fascinating world that is your immune system.

A River of Blood & Lymph

The immune system is a complex strategic fighting system powered by five liters of blood and lymph, a clear and colorless liquid that passes throughout the tissues of the body. Together, these two fluids transport all the different elements of the immune system so they can effectively do their jobs.

Your immune system is comprised of the skin, bone marrow, thymus, spleen, white blood cells, antibodies, hormones, and more. Learn more about some of those pieces and how to help your immune system.

White (Knight) Cells

Like white knights slaying a dragon, white blood cells charge into battle at the sign of trouble. The different types of white blood cells patrol your body with a variety of weapons, including antibodies that will overpower the offending organism. Some of them prefer just to eat the bacteria.

These brave soldiers only live up to a few weeks, so it's a good thing there's a lot of them – a single drop of blood can contain up to 25,000 white blood cells.  In conditions like leukemia, a blood cancer, as many as 50,000 white blood cells can live in a drop of blood.

Natural Killer Cells Are Awesome

These guys are the hit men of your body. Armed with a protein that breaks down a cell's membrane, natural killer cells seek out cells with abnormal membranes or outside covers, such as tumor cells and cells that are infected with a virus.

When natural killer cells spot someone they don't like, they kill them on contact. But like other white blood cells, these guys are the good guys.

Fever & Inflammation Are Good Things

While fever and inflammation are unpleasant symptoms, they are signs that your body is doing its job. Fever releases white blood cells, increases metabolism, and stops certain organisms from multiplying.

Inflammation is merely the result of each damaged cell releasing histamines, which in turn cause the cell walls to dilate. This creates the redness, heat, pain, and swelling of inflammation. This allows your body to limit the effects of the irritant.

Sleep Now or Forever Hold Your Peace

Been running around like crazy and all of a sudden you're sick? Well, that's your immune system getting its revenge.

If you're not getting more than five hours of sleep a night, your immune system can become depressed, just like you. This leaves you open to colds, flu, infection, and other things that will take you away from the things you've been sacrificing sleep for.

Some Sun is Good

Exposure to sunlight is the way your body naturally produces vitamin D. This helps ward off an array of bad things like depression, heart disease, and certain cancers. It's even good for people with autoimmune disorders.

A fair-skinned person needs only about 10 minutes on a sunny day to get all the vitamin D they need. However, too much sun (to the point of sunburn) can cause temporary damage to your immune system.

Stress Damages Your Immune System

Your immune system is ready for anything you can throw at it, but sometimes, it can only handle so much. 

Stress hurts your body in many ways, but it has the most significant effect on your immune system. During stress, a series of events release cortisol, a hormone from the adrenal gland that helps your body cope.


The saying goes that laughter is the best medicine, and there's truth to that. Laughter releases dopamine and other feel-good chemicals in the brain, all of which can help decrease stress.

Twenty minutes of laughter a day may not keep the doctor away, but it may help keep your immune system working properly.

Be Careful When Pumping Iron

Don't you hate when someone doesn't wipe down a machine after using it at the gym? Besides being gross, it's a good way to get everyone sick.

While everyone at the gym is getting ripped, the bodies going the extra mile are producing excess amounts of cortisol and adrenaline, the same chemicals produced during stressful periods.

So when you're in the gym, pace yourself and avoid any puddles on the stationary bikes.

You Need Germs to Stay Healthy

Your gut is filled with tons of bacteria and other things to help you digest your food. But germs outside your body are normally regarded as vile, disgusting things. While some of this may be true, you need those germs to stay healthy. 

Your immune system can adapt to things, which is why human beings have been around for so long. Once your body comes in contact with a foreign substance, it attacks it and remembers it. If it comes back, your body knows what to do. This is most apparent with measles: one infection is usually enough to protect you for life.


Anyone who experiences seasonal allergies or hay fever probably want to curse out every molecule of pollen or dander around them. This microscopic little buggers cause the release of histimines, which create all of the nasty symptoms of allergies. 

Allergies affect some and not others because of the way their body attempts to protect itself against the allergens.

Your Hyperactive Immune Disorder

In some people, their immune system attacks tissues in the body, causing disease. This is called autoimmunity.

Most peoples' immune systems get used to their own tissue before they are born. It does this by turning off the cells that would attack them. Autoimmune disorders are when the body mistakenly attacks healthy tissue. This is what occurs in people with multiple sclerosis, lupus, rheumatoid arthritis, psoriasis, and other conditions. They are treated with drugs that suppress the immune system.

It turns out your immune system isn't always the good guy.

Learn More

Now that you've learned some of the odder points of your immune system, you can help keep it healthy so it can keep you healthy. That includes getting enough rest, laughing a lot, and being mindful of your sun exposure.

Then again, those with autoimmune disorders know that keeping their immune system in check takes more than that. Learn more about immunodeficiency disorders and how they affect the immune system.