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.

Your immune system protects against disease, infection, and helps you recover after an injury.

The immune system is a complex fighting system powered by five liters of blood and lymph. Lymph is a clear and colorless liquid that passes throughout the tissues of the body.

Together, these two fluids transport all the elements of the immune system so they can do their jobs.

Like white knights slaying a dragon, white blood cells charge into battle at any sign of trouble. There are two different types of white blood cells: phagocytes and lymphocytes.

Phagocytes can move through your blood vessels and tissue to ingest or absorb invaders. Phagocytes target organisms that cause disease (or pathogens) and toxins. Toxins are a natural poison produced by some organisms as a form of protection. Sometimes when a phagocyte has absorbed a pathogen, it sends out a chemical that helps lymphocytes identify what kind of pathogen it is.

Each pathogen carries a specific type of antigen, and each lymphocyte in your body carries antibodies meant to fight the antigens carried by pathogens. There are three main types of lymphocytes in the body: B cells, T cells, and natural killer cells.

B cells create antibodies that attack bacteria, viruses, and toxins that enter the body. T cells kill cells in the body that have been overtaken by viruses or that have become cancerous. Like T cells, natural killer cells kill infected or cancerous cells. But instead of producing antibodies, they make a special enzyme, or chemical, that kills the cells.

Your body creates new antibodies whenever it’s infected with a new antigen. If the same antigen infects you a second time, your body can quickly make copies of the corresponding antibody to destroy it.

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.

Having a fever and inflammation can be unpleasant, but they’re signs that your body is doing its job. Fever releases white blood cells, increases metabolism, and stops certain organisms from multiplying.

Inflammation occurs when each damaged cell releases histamines. The histamines cause the cell walls to dilate. This creates the redness, heat, pain, and swelling of inflammation. As a result, your body limits the effects of the irritant.

Have you been running around like crazy, and suddenly find yourself sick? 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, and infection.

Exposure to sunlight is how 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 only needs about 10 minutes on a sunny day to get all the vitamin D they need. However, too much sun can cause temporary damage to your immune system and eventually lead to skin cancer. Remember some sun is good, but you need to protect your skin when you plan to spend time outside.

Skincare experts recommend all people wear sunscreen with broad-spectrum UVA and UVB protection, Sun Protection Factor (SPF) 30 or higher, and water resistance. When the sun is very strong, you should also wear protective clothing, such as:

  • long-sleeved shirts
  • long pants
  • wide-brimmed hats
  • sunglasses

Also, stay mostly in the shade when the sun’s rays are strongest, between 10 a.m. and 2 p.m.

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

Stress has a significant effect on your immune system. During stress, a series of events release cortisol, adrenaline, and other stress hormones from the adrenal gland. Together they help your body cope with stress. Normally, cortisol is helpful because it decreases the inflammation in the body that results from the immune responses caused by stress.

But if a person is chronically stressed, stress hormones can affect the way the body functions over time. This increases your risk of health problems, including:

  • anxiety
  • depression
  • digestive issues
  • heart disease
  • sleep disorders
  • weight gain
  • problems with memory and concentration

It’s important to find healthy ways to deal with your stress. This will decrease your risk of long-term stress and its related health problems. Some good ways to reduce stress include:

  • meditation
  • yoga
  • acupuncture
  • talk therapy
  • art therapy
  • exercise
  • eating healthfully

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.

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 and disgusting. While some of this may be true, you need those germs to stay healthy.

Your immune system can adapt, 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 wants to curse every molecule of pollen or dander around them. These microscopic particles cause the release of histamines, which create some of the nasty symptoms of allergies.

Allergies don’t affect everyone. They’re caused when your body mistakes something harmless, such as pollen or a type of food, as a pathogen. Your body launches an immune response against it, causing you to experience allergy symptoms.

Sometimes your immune system attacks the tissues in the body, causing disease. This is called autoimmunity.

Most people’s immune systems get used to their own tissue before they are born. They do 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 autoimmune diseases such as:

  • multiple sclerosis
  • lupus
  • rheumatoid arthritis
  • psoriasis

These diseases are treated with drugs that suppress the immune system.

Your immune system works hard to protect you every day, but there are things you can do to help it out:

  • Get a good night’s sleep. Your body can’t
    function correctly if you aren’t sleeping well.
  • Practice good hygiene. Washing your hands
    regularly can prevent infections.
  • Eat a balanced diet and get plenty of exercise. Eating
    nutritious food and staying active will help your body fight off infections.