Woman boxer training to fighting off immune challenges

How Does the Immune System Work?

Published: November 2021 | Updated: November 2021

Staying well may seem like a challenge, especially as cold winter months approach and your time indoors increases. Luckily, your body has a natural line of defense: your immune system.

Fortunately, it's fairly simple to support your immune health: healthy lifestyle choices are your most important weapon to arm your immune system so that it's ready for when foreign substances attack. Everything from what you eat to how well you sleep plays an important role in keeping your immune system healthy.

What is not so simple, however, is how the immune system works. So, let's dive into the most frequently asked questions about how this intricate network of cells, tissues, organs and other substances protects our health.

What are the 3 major functions of the immune system?

Sick woman on couch needs help from her immune system

Your immune system is your first line of defense against disease and illnesses. How does it manage to guard your health so masterfully? There are actually three distinct things the immune system does so that you can remain healthy:

  1. Fights off infection.

    First, your immune system is tasked with fighting off foreign cells and pathogens. Without a healthy immune system response, bacteria, viruses, and other germs that we come into contact with each day could compromise our health.
  2. Protects us from the environment.

    Second, your immune system helps to protect you by fighting off the environmental substances that we encounter—toxins, heavy metals and other chemicals, and more—all of which could be harmful to our health.
  3. Keeps your cells functioning normally.

    Lastly, your immune system is responsible for maintaining a healthy balance of normal cells throughout your body by removing dead cells (also called "senescent" immune cells) and being on alert for any abnormal cells, such as cancer cells, that could develop into a disease.

Innate and adaptive: the two major parts of your immune system

Doctor giving vaccine that help develop adaptive immune system

In addition to these three functions of the immune system, there are also two parts: your innate immune system and adaptive immune system.

Innate immune system: As the word "innate" suggests, your innate immune system is the immune system that has been actively protecting you since birth. Comprising your innate immunity are specific body parts, such as your skin and the mucous membranes that line your respiratory and gastrointestinal tracts, which protect your body from harmful substances so that you stay healthy, as well as immune cells. The innate immune system is the first responder to any threats to your immune health—and because of it, most foreign invaders usually don't stand a chance of entering your body and bloodstream!

Adaptive immune system: On the other hand, the adaptive immune system is continuously developed throughout your life. It basically "learns" from the various threats you've encountered over the years by creating antibodies to protect your body from these invaders if they try to cross your path again! An antibody is formed after the first exposure to a harmful substance—after which, your adaptive immunity system will recognize it and defend against it much faster. In addition to previous exposure to pathogens, vaccinations help build up your adaptive immune system by training it to make antibodies.

Is the immune system always working?

Your immune system is working 24 hours a day, 7 days a week (yes, even as you sleep!) to keep you healthy and protected against foreign invaders and microorganisms.

Your immune system is ready, willing, and able to act whenever it is needed. For example, if you were to get bitten by an insect, your skin might become itchy, and a red bump might appear. That itchy bug bite is a signal that your immune system was triggered and is working to detect what foreign substance or invading pathogen entered your body. After some time, your immune system cells fight off the damage caused by the bite and regenerate naturally.

Is skin part of the immune system?

Woman touching face while looking in the mirror

You may not realize it, but your skin plays a critical role in helping support your immune health. Your skin is the primary barrier between your internal systems and the world around you, acting as a shield between your bloodstream and foreign particles. In fact, your skin has around 20 billion  T-cells (cells that are part of your immune system) which help fight back against specific foreign particles.

Keratinocytes, which produce keratin, also help support your immune health by detecting antigens and sending white blood cells to the infected area. This part of your skin's immune system helps your body respond appropriately to when you have an injury (or simply an infected zit that you tried to pop!); not only does it help wounds heal, it also helps protect against infection.

What are the different types of immunity?

Woman breastfeeding her baby to provides natural immunity

Ever notice that children tend to have runny noses more often than adults? Each person's immune system is different, but in general, most of us develop higher levels of immunity as we transition from infancy to childhood and adolescence. We can thank that adaptive immune system for this increased resilience—after all, it's responsible for cultivating stronger immune health by creating antibodies to the pathogens that laid you up in bed when you were younger.

There are several different types of immunity which keep you strong at different phases in your life: active natural, active artificial and passive natural.

  • Active natural:

    This is an "active" immune response that your body acquires from being exposed to foreign invaders. An encounter with a pathogen causes your immune system to actively recognize the germ and immediately get rid of it.
  • Active artificial (i.e. vaccines):

    Immunizations produce a response from your immune system that is called active artificial immunity. For example, some types of vaccines offer your body a weakened form of a pathogen—and your body reacts by activating an immune response and making antibodies. (This is why you might feel unwell after a shot—which is actually a good thing because it means your body is gearing up for a response when it encounters the real thing!)
  • Passive natural (from pregnancy and breastfeeding):

    This occurs when a baby's immune system is provided antibodies from the mother—their natural immune health develops during their time in the womb and increases if the mother breastfeeds, further exposing her child to antibodies.

Ways to support your immune system

Bowl of steamed broccoli for immune support

If you are prone to feeling under the weather (or you're just a germophobe), you don't need to live in a plastic bubble to avoid getting sick. In fact, with the healthy lifestyle changes like a well-balanced diet, exercise, sleep, and hygiene, you can support your immune health day after day.

Just follow these simple do's and don'ts:

DON’T: Smoke

If you are looking to make a healthy lifestyle change that will not only help support your immune system, but overall health, then it is time to quit smoking cigarettes, cigars – and especially vaping. Smoking harms the immune system and impacts its ability to fight foreign invaders, making it harder for you to recover when you are feeling under the weather.

DO: Eat a well-balanced diet

Fueling your body with immune supporting foods is excellent way to help support your immune system and keep it strong. Your best bets include:

  • Citrus:

    Citrus fruits are a great source of vitamin C, which help support immune health by increasing the production of white blood cells. Stock up on oranges, including naval, clementine, and tangerines. Want a little less sweet and a little more zest? Go for grapefruit, lemons and limes, which also are packed with immune supporting vitamin C.
  • Broccoli:

    A great source of vitamins and minerals, broccoli is brimming with powerful antioxidants and is one of the healthiest veggies you can eat. The secret to keeping broccoli bursting with vitamins and minerals is to cook it as little as possible; if you don't love it raw, steaming is your second-best choice.
  • Spinach:

    This leafy green is packed with vitamin C and other antioxidants to help support your immune health. Sautee it with extra-virgin olive oil and a little garlic for a delish side dish!
  • Almonds:

    Vitamin C gets a lot of praise when it comes to supporting your immune health, but vitamin E deserves a little credit as well because it's an antioxidant—and antioxidants are famous for supporting a healthy immune response. So be sure to save some room on your plate (or even your pocket) for almonds, which are great source of vitamin E.

DO: Exercise

Breaking a sweat is one of the best ways to support a healthy immune system. A workout not only helps keep your lymphatic system flowing, but also supports general immune health so you can keep fighting off foreign invaders. Plus, that healthy sweat is a great way to detox!

Make sure to exercise in moderation and start slow and listen to your body – don't push yourself too hard. For beginners, start slow and take a walk for 30 to 45 minutes each day, or try stretching with a yoga class.

DO: Sleep well

Man sleeping to support immune health

Did you know that staying healthy is so easy, you can do it in your sleep? It's true! Sleep is an important part of your overall immune health because it provides a period of rest for your body to recharge and fight off foreign invaders.

Sleep also plays an important role in developing your immune system "memory," so it is better at recognizing and responding to foreign invaders—in fact, getting enough shut-eye even has been shown to help improve the body's response to vaccines.

It is important to get at least seven hours of uninterrupted sleep each night—and if you are sick of counting sheep or can't quite stay asleep after you hit the hay, here is a helpful guide to get to sleep faster.

Pro tip: the hormone melatonin not only promotes restful sleep, but it also has immune health benefits.

DO: practice good hygiene

Good hygiene goes a long way, especially when it comes to supporting your immune health. Your skin is your body's first line of defense, so to keep germs away it is important to:

  • Wash your hands with soap and water before touching food and after using the bathroom or handling garbage.
  • Cover your mouth and nose when you sneeze, use a tissue (or your elbow if you don't have one handy), and make sure to wash your hands immediately after.
  • Wash all wounds with an antiseptic and bandage immediately.
  • You may be tempted to pop a pimple or pick a healing wound, but resist the temptation! Doing so allows germs to enter your body.

References

By: Andrew Davis, Health & Wellness Writer

Andrew Davis is a graduate of Pace University NYC with a Bachelor of Arts in Psychology. He has more than a decade's worth of experience in content and social media in the health and wellness space. An avid traveler, Andrew also has volunteered as an English teacher and humanitarian in countries throughout Asia.

Scientifically Reviewed By: Michael A. Smith, MD