Immune system 101: how immunity works + 4 ways to boost your immune system

During times when we’re facing a new health threat like COVID-19, we talk a lot about our immune systems. However, people should really focus on building up immunities all the time, says Dr. Chris Andershock, medical director at BlueCross BlueShield of Tennessee.

“The immune system is basically a series of layers, or walls, of protection around you,” says Dr. Andershock. “It starts with your skin and hair, and it includes everything from lymph nodes to T cells — all the barriers that prevent harmful particles from getting into your body.” 

How does your immune system work?

Dr. Andershock: Cells have the ability to prevent particles from being absorbed. Skin, for example, is like a soldier standing guard. If something penetrates the skin, it will trigger an early warning system that tells your body there’s a potential pathogen. 

Everything from the hairs in your nose to the cilia in your lungs is part of the immune system. If it’s working as it should, it will catch and sweep out viruses, bacteria, fungal spores and any other particles that can make you sick. When something makes it past those first lines of defense, it should be detected by your lymphatic system. If you’ve ever had swollen lymph nodes, it’s likely your body was fighting off infection. 

What kinds of immunity does your body have?

Dr. Andershock: In general, there are 2 types of immunity:

  • Innate immunity, which is something already present in the body, and
  • Adaptive immunity, which is created in response to being exposed to a foreign substance.

How has COVID-19 affected immune systems?

Dr. Andershock: A big part of our immune system relies on recognizing infections it’s come into contact with before (adaptive). Because it is new, no one had exposure to it before the COVID-19 pandemic. That means your body doesn’t have a memory of being challenged with a virus like this before, which takes antibodies out of the picture. 

You still have general immunities, of course, as part of your innate immune system. They may recognize dangerous cells and attack them. But this general defense is not as good as specific past experience would be. That’s a big reason the death rate is so much higher, especially in people with impaired immune systems. 

Dr. Suzanne Corrington explains what you need to know about how vaccines work and what to expect when you get one.

What are the signs your immune system isn’t working properly?

Dr. Andershock: People who are immunocompromised are likely to contract diseases more easily and often than the average person. Look for:

  • Recurrent infections that are frequent, severe or caused by things that don’t typically cause infection in regular people. Chronic sinus infections are a good example of this type of immunodeficiency. 
  • Unusual rashes, specifically on the palms of hands, soles of feet or other places you don’t typically see rashes.
  • Recurrent or chronic intestinal problems, which can be caused by inflammation or reduced immune response to pathogens that get through the gut lining. 
  • Prolonged healing of wounds. 

What things can people do to build up their immune system?

For the most part, you improve immunity by improving health, and you know how to do that — don’t smoke, eat healthy, and exercise. For immunity in particular, focus on 4 things:

1. Get quality sleep

Dr. Andershock: We need to start with sleep. Getting enough rest is arguably the single most important thing you can do to improve your immunity, and your health overall. 

7 tips for sleeping soundly

2. Be mindful of your environment

Dr. Andershock: It’s important to consider the air quality around you, and that includes inside our homes. Are you constantly breathing in animal dander and dust? Are you changing your air filters regularly? Is the air in your home humid or dry? Outside, can you avoid areas with pollen and pollutants?

You have to be purposeful in addressing the allergens that can create low-level inflammation, which runs down the immune system. 

WellTuned guide to inflammation

3. Increase exercise and sunlight

Dr. Andershock: It’s important to change up your environment from time to time. Make daily exercise part of your routine. You don’t have to join a gym or compete in a triathlon. Schedule a daily walk and get some vitamin D. You’ll be surprised how much better your body feels. 

How walking for 20 minutes a day can improve your quality of life

4. Boost your nutrient intake

Dr. Andershock: A well balanced diet with lots of vegetables and fruits goes a long way toward boosting your immune system. If you’re already eating well but still feel run down, consider increasing the following nutrients, preferably through healthy foods, or talk to your doctor about supplements.

Zinc aids recovery from viral infections and has anti-inflammatory and antioxidant properties. Foods that are high in zinc include chicken, red meat, oysters, crab, beans, nuts, whole grains, fortified breakfast cereals and dairy.

Vitamin C supports cellular functions of both the innate and adaptive immune systems. Foods that are high in vitamin C include cantaloupe, citrus, bell peppers, strawberries, broccoli, tomatoes, kale and snow peas. 

Vitamin D helps regulate both immune responses, and it decreases susceptibility to infection. Foods that are rich in vitamin D include fatty fish (salmon, herring, sardines), canned tuna, egg yolks and mushrooms. 

Vitamin B complex includes many types of B vitamins, such as B1 (thiamine), B6 and B9 or folate. B vitamins are essential in the production of blood cells (red, white and platelets); they support chemical reactions in the immune system; and they’re needed for cellular reproduction by DNA and RNA synthesis. Foods that are high in vitamin B include cold-water fish (salmon, tuna), chicken, green vegetables and chickpeas. Foods that are high in folate include peas, lemons, bananas and melons. 

More from Dr. Andershock:

Ashley Brantley

Ashley Brantley has been writing about food, culture and health for more than a decade, and has lived in three of Tennessee’s four major cities (Memphis, Nashville and Knoxville).

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Ashley Brantley has been writing about food, culture and health for more than a decade, and has lived in three of Tennessee’s four major cities (Memphis, Nashville and Knoxville).