Most people are not very familiar with the functions of the immune system. However, ever since insects evolved, there has been some form of immunity that has a flexible response to various infectious agents and other environmental irritants.
In this article, you will learn some immune system facts related to both parts of immunity — innate and acquired (adaptive) — which interact together and exchange information continuously to keep us protected.
Furthermore, we displayed for you the most relevant statistics on the common immunity-related diseases, and, to fresh it up, we punched in with some seriously fun facts about the immune system.
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The Top 10 Immune System Statistics
- About 98% of thymocytes die in the thymus during negative selection.
- After puberty, the thymus shrinks by about 3% every year.
- Оne in every 500 individuals is affected by a primary immunodeficiency.
- Being too clean can increase your risk of getting an autoimmune or allergic disease.
- A healthy diet with sufficient quantities of proteins supports humoral immunity.
- Disease symptoms may represent the immune system doing its job, according to immune system statistics.
- Allergies are an example of the immune system overreacting to harmless antigens.
- Vitamin D is a hormone that modulates immune functions.
- Autoimmune diseases are more common in women.
- The immune system can be trained.
Now that you have read some of the facts and stats cherry-picked from the article, it’s time to dig deeper. Below you’ll find a ton of useful information regarding the immune system and more stats and facts to expand your knowledge. Enjoy!
Facts About the Immune System and its Cells
1. Humans have between 4,500 and 11,000 white blood cells in each microliter of blood.
The average number of white blood cells — which are mainly immune cells — depends on age and sex. However, the number of these cells can be lowered or elevated as a result of various diseases, making the complete blood count testing a routine investigation.
2. Most of the immune cells reside in tissues and not in the blood.
Besides the central immune organs such as thymus and bone marrow (where the immune cells come from and become immunocompetent), most of the immune cells are widespread in the peripheral immune system parts. These include lymph nodes, spleen, liver, mucosa of digestive and respiratory systems, skin, etc. Consequently, they can detect, react, and eliminate every pathogen that they encounter, ensuring a robust immune system defense.
3. About 98% of thymocytes die in the thymus during a process called negative selection.
The majority of future T lymphocytes, or the so-called thymocytes, fail during the development processes and die. Only the remaining 2% survive and leave the thymus as T cells, which can become immunocompetent. This is undoubtedly one of the most interesting facts about the immune system.
4. Hundreds of millions of different B cells circulate in the body.
The reason for this seemingly large number is the biological requirement of our body to recognize every single pathogen. Each B cell produces a unique antibody which is specific to a particular unknown or danger molecule.
5. Cytotoxic immune cells are involved in both anti-infectious and anti-tumor immunity.
These cells are cytotoxic immune cells and natural killer cells (NK cells), representing specific and nonspecific immunity, respectively. By killing virus-infected or tumor-host cells, they seek to limit the complications of pathological processes.
Facts About Immune System Organs
6. The lymph node is the principal meeting place of the immune system and antigens.
Independently from where the pathogen enters the body, usually, it’s delivered to the regional lymph nodes, where T and B lymphocytes reside, waiting for danger signals.
7. The thymus shrinks by about 3% yearly throughout middle age.
In the process called involution, the thymus is replaced with fat tissues after puberty. This is one of the most interesting thymus facts, showing that in older people, the expansion and regeneration of T cells play a role more significant than their production.
8. The spleen provides crucial support in antigen presentation to the immune cells.
Besides its other roles in the function of the immune system, important facts reveal that the spleen also aids hematopoiesis and red blood cell clearance, thus regulating the T and B cell response. Although you can live without a spleen, it was shown that surgical splenectomy due to trauma or diseases leads to severe dysregulation in immune functions to pathogens.
Since the immune responses to encapsulated bacteria are the most altered, splenectomized people are more prone to meningitis and sepsis. People who don’t have a spleen should take additional conjugated vaccines against specific pathogens.
Statistics on Immune System Diseases
9. Disease symptoms may represent the immune system doing its job.
Signs such as fever and inflammation can be seen in several diseases. They are part of the normal physiology of the immune system and are usually good signs. However, the cytokine storm or the release of a vast quantity of immune mediators, which can also be a part of the inappropriate immune response, denotes a bad prognosis due to many complications, including multiorgan failure and death.
10. Autoimmune diseases are more common in women.
The immune system facts unconditionally showed that women are more prone to the development of an autoimmune disease, probably due to hormonal factors. The female to male ratio is 10:1 for Hashimoto’s thyroiditis, 9:1 for systemic lupus erythematosus, 9:1 for primary biliary cirrhosis, 2.5:1 for rheumatoid arthritis, 2:1 for multiple sclerosis, etc.
11. Allergies are an example of an overreaction of the immune system to harmless antigens.
The allergic reaction is a nonspecific response to a specific molecule, such as pollen or dander, which leads to the release of histamine and other mediators. They are associated with unpleasant allergy symptoms that vary from mild, such as sneezing, to severe ones, including death.
12. Оne in every 500 individuals is affected by a primary immunodeficiency.
According to the current immune system information, there are over 400 different primary immunodeficiencies (PIDs). They can be diagnosed at any age, from early childhood to adulthood. The clinical manifestation of PIDs could be followed by recurrent, severe, unusual, or difficult-to-treat infections. It‘s important to remember that PID patients are at risk of other complications, including the occurrence of autoimmunity and malignancies.
13. Sleep deprivation, lack of physical activity, and stress can weaken the immune system.
All of these factors are proven to deteriorate the immune functions by different mechanisms. Moreover, chronic insomnia can influence the decline in white and red blood cell production.
Fun Facts About the Immune System
14. The immune system can be trained.
The immune cells have been training since their nascence, first in the thymus, and then in the circulation and tissues by encountering different pathogens. However, vaccines are also a way to train immune cells by avoiding complications arising from a real infection.
15. Being too clean can increase your risk of getting an autoimmune or allergic disease.
According to the “hygiene hypothesis,” although washing and disinfecting hands is the best way to avoid infection, this may increase the incidence of autoimmune and allergic diseases, according to the immune system statistics and pathogens-associated infection reports. This is especially valid for Western countries, where minimizing the meeting of some pathogens leads to the development of immune diseases.
16. Laughter helps our immune system to manage stress.
Twenty minutes of laughing a day leads to the release of dopamine and other hormones, which make us feel better, decrease stress, and help the immune system work properly. In such a way, laughter can be considered as a non-specific defense mechanism.
17. How friendly and extroverted you are may depend on your immune system.
One of the most interesting immunity facts comes from a scientific study that shows that the immune system could play a role in controlling social behavior through the interferon-gamma (IFNγ) cytokine. From an evolutionary perspective, the immune system may be activated to protect us from infections during socialization. This molecule can also be the link between immunity and neurological and psychiatric disorders, including autism.
18. As we get older, the immune system ages too.
The immune functions decline with aging, including dysfunction in the chemical barriers of innate immunity, adaptive immune cell activation, etc. This phenomenon explains why secondary immune deficiencies or autoimmune diseases may occur in older people.
How Food Impacts the Immune System Physiology
19. Vitamin D is a hormone that modulates immune functions.
Since deficiency and insufficiency in vitamin D are associated with susceptibility to infections, autoimmunity, or other problems, getting sufficient amounts of vitamin D through food and supplements can boost the immune system. It can also prevent many other complications associated with bone homeostasis.
20. A healthy diet with sufficient quantities of protein supports the humoral immunity.
A balanced diet is essential for well-being and maintaining a healthy immune system. Getting enough protein will help you fight off infections, particularly through the proper production of antibodies. The scientific facts about the immune system confirm that poor nutrition and some diets may lead to immune dysfunction that can alter humoral immunity, including a lack of flu-shot antibodies or other antibodies after vaccination.
21. Zinc is an essential micronutrient for cell-mediated immunity.
Many conditions, such as growth retardation, cognitive impairment, and immune dysfunctions, are attributed to zinc deficiency; thus, it makes sense to supplement it in the case of lower levels in the body. Some of the best foods to boost the immune system by increasing zinc consumption are meat, shellfish, legumes, nuts, dairy products, eggs, and whole grains.
Why is the immune system important?
The immune system provides all the protective mechanisms needed to fight off infections or other dangerous agents. It helps us clear the dead microorganisms after treatment, toxins, etc. Without the immune system, we wouldn’t be able to survive, not only because of the pathogens (viruses, bacteria, fungi, etc.) around us but also because the immune system is involved in the protection of tumor cells.
How does the immune system work?
The immune system works on many levels and through different mechanisms. First, the antigen is welcomed by the innate cells, which are responsible for the initial immune response and presentation to lymphocytes. T and B cells then recognize the antigen and activate, leading to the creation of specific immunity and the production of antibodies. Some of the activated T and B cells remain as memory cells, ready for rapid activation upon re-encounter with the same antigen.
Do flu shots weaken the immune system?
No, neither flu shots nor other vaccines weaken your immune system. The principle of vaccinations is to prepare the immune system for the possible encounter with pathogens. A real infection (flu, morbilli) leads to an immune system that could be weak for months. Furthermore, vaccinated people may also get the flu, but the infection is milder.
Regardless of the disadvantages of the immune system, such as being extremely energetically expensive or needing to be tuned to avoid the overreaction and development of immune-mediated conditions, the protection that it ensures is necessary to sustain life. The immune system facts can help us realize the essential role of our immune system in safeguarding our body.