26 Captivating Immune System Facts for 2024

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Since we’re still in the middle of the global COVID-19 pandemic, we’ve prepared some immune system facts for you that might come in handy. In the present circumstances, everyone wants to boost their health. But, let’s be honest, there are a lot of things we don’t know about the way the human body functions. 

So what is the immune system, and how does it protect us from diseases? Don’t worry, we’ll walk you through the whole thing. Let’s get started.

Top 10 Facts About the Immune System

  • We’re about 43% human if we count all the cells.
  • White blood cells constitute nearly 1% of the blood.
  • Our immunity has a memory.
  • Bacteria in our body weigh between two and five pounds.
  • Not all the bacteria that live in the body are harmful—some are actually helpful.
  • The immune system can attack itself.
  • The gut contains 80% of the immune cells and 100 trillion microorganisms.
  • Allergies come from our immune system.
  • A strong immune system won’t prevent you from contracting the coronavirus.
  • Our immune system is made, not born.

The Immune System: Important Facts and Terminology

We can think of our immune system as our body’s version of the military. It protects us against diseases and helps us recover after an injury. While most of us know its fundamental function, there are many things about our body’s natural defense system that we may not be aware of. So let’s dig a little deeper.

1. The immune system is not a single unit, but it consists of many parts.

(John Hopkins Medicine)

An interesting fact about the immune system is that it consists of two main parts. The first one is the innate immune system. That is the first line of defense of the body, and we are born with it. The second one is the adaptive immune system. It is slower, more targeted, and develops as we are exposed to new pathogens. In essence, these two systems act as a team.

2. One of the not-so-fun immune system facts is that our immune system can attack itself.


The immune system’s task is to defend the body against damaging foreign bodies. But sometimes, it can’t tell the difference between harmless and dangerous situations. When that happens, white blood cells can’t distinguish between the pathogens and the body’s normal cells. That causes the immune system to destroy its own healthy tissues.

3. One of the more interesting facts about the immune system is that if there is any sign of trouble, white blood cells fight to knock out the invaders.

(Franklin Institute)

White blood cells are on the lookout for signs of disease all the time. If germs appear, they have particular tactics to destroy the enemies. In some situations, white blood cells produce protective antibodies to wipe out the germs, while in other, they surround and destroy the bacteria.

4. One of the cool facts about the immune system is that we need to make peace with the germs in our body since they’re not all bad.

(Harvard Medical School)

There is an infinite number of microbes that live in and on our bodies. What’s interesting though, is that we actually need some of them to maintain good health. The good microbes provide us with the essential nutrients and protect us against the bad. Our body needs to maintain a balance because when the good bacteria can’t defend us, the bad takes over and makes us sick.

5. The gut contains around 80% of the immune cells and 100 trillion gut microorganisms.

(Danone Nutricia Research)

With such a large percent of the immune system in the gut, the phrase “trust your gut” could actually become a wellness tip. So in general, the state of our gut determines how we feel and behave physically and mentally. But one thing’s for sure, the secret to a healthier life lies in the balance of good and bad bacteria. Well-developed gut microbiota is related to improved health and reduced risk of allergies, which is why so many people find great value in reliable prebiotic supplements.

Interesting Facts About the Immune System

We’ve already established that the immune system is our biological bodyguard. Since it plays such an important role, read on to learn some more incredible facts about it.

6. White blood cells constitute nearly 1% of our blood.

(Libre Texts)

White blood cells are the most powerful weapon in our immune system. They are our white knights in shining armor, always ready to fight foreign invaders. As shown by the immune system statistics, there are only 1% of white blood cells in five liters of blood in an adult’s body, but that’s more than enough to get the job done.

7. We’re only about 43% human if we count all the cells.


Half of our body is not human. There are only 43% of human cells in the body, and the rest are microscopic colonists. This cool fact about the immune system suggests that understanding our microbiome would help us to understand diseases better.

8. Bacteria in our body weigh between two and five pounds, as much as an average brain.


Our body contains trillions of bacteria, viruses, and fungi. Collectively, they are known as the microbiome, which weighs about two to five pounds. One of the fun facts about the immune system is that that’s roughly the weight of an average brain.

9. Allergies come from our immune system.

(John Hopkins Medicine)

Allergies are a very common health condition across the world. Allergic reactions happen when our immune system overreacts to a substance and treats it as harmful, producing antibodies to attack it. What’s more, based on the available immune system facts and functions it typically performs, we know that the immune responses can be mild to life-threatening.

10. Our immune system has a memory.


Immunological memory is the capacity of the immune system to respond more quickly and effectively to infectious agents it has already encountered before, i.e., its ability to learn and remember specific pathogens. To top that off, the adaptive immune system facts show that it can also provide long-standing protection against recurring infections.

 The concept of immune memory is based on the body’s capability to create antibodies against different pathogens. In a nutshell, we can say that our immunity has a memory bank.

Facts About the Immune System and COVID-19

Since the start of the coronavirus pandemic, people have been looking for ways to boost their immune systems. After all, our bodies’ defenses need to be as strong as possible. So how can we protect ourselves from this new virus? Curious to find out? Take a closer look at the following section.

11. The interaction of the microbiome with the immune system is very important for the antiviral immune response.

(Infectious Microbes & Diseases)

The immune system facts reveal that the gut microbiota provides signals to regulate the immune cells for inducing or subduing an immune response. These signals are necessary for the activation of the immune system under certain conditions. Therefore, the role of the gut microbiota in controlling immunity and in the impact of coronavirus infection is very important.

12. At least one in five admitted COVID-19 patients develop new antibodies that attack their tissue within a week of hospitalization. 

(Stanford Medicine)

COVID-19 has a massive impact on the human immune system and microbiome. The immune system statistics link the coronavirus to an increase in self-attacking antibodies. The autoantibodies can be early signs of a developing autoimmune disease.

13. One of the more encouraging immune system facts is that the regulation of the immune system can contribute to the control and elimination of viral infections.

(Infectious Microbes & Diseases)

SARS-CoV-2 causes inflammation within the respiratory tract. Secondary respiratory bacterial infections have been an important cause of many deaths related to COVID-19. Since the microbiome immune interactions regulate such infections, the microbiota is crucial not only for the antiviral immune response but also for the disease’s outcome.

14. The immune system statistics indicate that around 90% of people who have encountered COVID-19 will have antibodies to it.

(British Society for Immunology)

One of the ways to fight off an infection is for B cells to create antibodies. These antibodies stick to the virus to mark it for elimination by the immune system. Another way is by activating T cells, which attack and kill any cells infected with the virus. The B cells, their antibodies, and T cells remain in the body after the infection has gone.

15. A strong immune system won’t prevent you from contracting the coronavirus, according to the available immune system facts.

(Intermountain Healthcare)

SARS-CoV-2 is a novel pathogen. That means those who contract it don’t have existing antibodies to create a defense. However, if you develop a strong immune system while you’re healthy, you can sustain your body and fight viruses better.

Immune System Facts and Myths

With the COVID-19 pandemic still raging worldwide, immunity is on everyone’s minds. We all wonder how we can improve our health and have come across many misconceptions about it. The following section will replace them with facts that will help you learn more about your own body.

16. Myth: Our immune system will never change.


One of the interesting facts about the immune system that you should know is that it ages just like everything else in our body. That’s why older people become more vulnerable to diseases as the immune system gets slower in responding to pathogens.

17. Myth: There is no real need for vaccination because many people who were not immunized in the past led long and healthy lives.


For example, before the vaccine for measles was developed, the immune system statistics show that more than 90% of people were infected by the time they reached the age of 10. Many people who survived the disease suffered major consequences. Although sometimes vaccine-preventable conditions aren’t severe, we can never know how seriously a particular disease can affect us. 

18. Myth: Seasonal allergies are manifestations of a weakened immune system.

(Ask the Scientists)

One of the immune system interesting facts is that seasonal allergies are actually caused by an overreactive immune response. It can be difficult to tell allergies apart from other upper-respiratory issues because they have many similar symptoms. The difference is that allergies aren’t triggered by viruses or germs.

19. Myth: Giving a child several vaccines at the same time overloads the child’s immune system.


The facts about the immune system clearly state that receiving more than one vaccine at a time won’t have any negative effects on a child’s immune system. Every day, children come into contact with several hundred foreign substances that trigger an immune response just through breathing and eating. In addition to that, children are exposed to more antigens from a common cold than from vaccines. 

20. Myth: We should take as much vitamin D as we can.

(Mayo Clinic)

Vitamin D toxicity is a rare and occasionally serious condition that occurs when you have too much vitamin D in your body. According to the available immune system facts, the major outcome of vitamin D toxicity is a buildup of calcium in the blood, which can cause weakness, nausea, and vomiting.

21. Myth: We are all born with good immunity.

(Scientific American)

Available facts about the immune system indicate that our immune system is made, not born. The strength of the body’s defenses isn’t genetically programmed—at least not entirely. That being said, while some people are lucky to be born with a good immune system, others have immune deficiencies since birth.

How to Boost Your Immune System

Every day, our immune system works hard to protect us. If you’re looking for ways to keep it strong, the section below may help you. Read the following cool immune system facts to learn more about how you can improve your health.

22. Work on your gut health.

(American Psychological Association)

Stress is associated with changes in gut bacteria, which have been shown capable of influencing mood. As per the immune system statistics we mentioned earlier, nearly 80% of the immune system is located in the digestive system. So it’s for the best to keep your stomach happy and healthy.

23. Get good sleep.

(Mayo Clinic)

Lack of sleep affects your immune system. The available immune system facts reveal that people who don’t get enough sleep are more likely to get an illness caused by a virus. Lack of sleep can also influence your recovery if you do get sick. Moreover, the production of antibodies that fight infections is reduced during the periods when you don’t get enough sleep.

24. Let the light in.

(Sage Journals)

Vitamin D has a significant role in regulating the adaptive and innate parts of the immune system. What’s more, the available facts about the immune system seem to indicate that vitamin D supplementation can prevent respiratory illnesses or improve their outcomes. If you can’t get outside and enjoy the sunshine, you can always consider taking high-quality vitamin D supplements.

25. Exercise at least 30 minutes per day.

(Medline Plus)

Exercising has numerous benefits. It can strengthen and improve different parts of the immune system. Crunching the immune system numbers shows us that physical activity may help flush germs out of the lungs and airways, which may lower your chances of getting ill. Find a fun indoor or outdoor exercise that you enjoy and stick to your routine.

26. Eat healthy, balanced diets.


Since the onset of the pandemic, there has been a pronounced uptick in the interest in the immune system, from interesting facts to ways to improve our immunity. Nutritionists agree that a poor diet is one of the main reasons we are more prone to cold-weather illnesses. 

There is no cure for the common flu, but eating well and getting enough vitamins may help you avoid getting sick. Since it’s not always easy to plan meals that would cover all of your nutritional needs, some people supplement their diet with appropriate doses of top-quality multivitamins.

Finishing Thoughts

Our immune system is our greatest defense against any virus or infection. Even if we have good immunity, we should never take it for granted. Fortunately, there’s no shortage of amazing facts about the immune system that can help you learn more about your health and how to improve it. Pay attention to the signals your body sends you, try to establish a healthy routine, and stick to it. Your well-being should always be your main priority.


Why is the immune system so important?

The immune system is vital for our survival. Without it, our bodies would be open to attack from germs, parasites, viruses, and much more. In short, our immune system is the key to our health.

At what age does your immune system weaken?

We’re only as young as our immune system. Our immune system loses strength as we get older. That is a crucial reason why people over the age of 70 are most at risk of getting a disease.

Can a weak immune system be cured?

The immune system important facts show that people with a weak immune system can take several steps to improve their health. Good hygiene is one of the easiest ways to stay healthy. In addition to that, eating balanced diets, getting enough good sleep, and exercising can also help to boost the immune system.

What percent of the US population is immunocompromised?

If someone is immunocompromised, that means their immune system’s defenses are low. The immune system statistics state that, at the moment, people with a weakened immune system account for about 44% of US patients hospitalized with breakthrough COVID-19 infections, even though only 2.7% of the entire US adult population is immunocompromised.

At what age is your immune system strongest?

The immune system continuously matures during childhood and is fully developed by the age of seven or eight. Compared to many other functions of the body, most people’s immune systems work great at any age. Even though the immune system tends to get weaker with age, there’s a lot you can do to boost it. Luckily, the immune system facts we presented here can go a long way towards helping you stay healthy.

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Table of Contents
Top 10 Facts About the Immune System The Immune System: Important Facts and Terminology Interesting Facts About the Immune System Facts About the Immune System and COVID-19 Immune System Facts and Myths How to Boost Your Immune System Finishing Thoughts
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