What Is The Immune System

by Prachee last updated -

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The immune system of a person protects him or her from being attacked by various bacteria and viruses. Without us even realizing, the system is working 24/7 to keep our body free from the microorganisms that can harm us.

What is the Immune System?

Our immune system is the intricate network of interconnected organs which is our body’s second line of defense. The first line of defense includes physical barriers such as skin and mucous membranes. Mucous membranes cover the interior of walls of the digestive, respiratory, and reproductive systems.

If external microorganisms such as bacteria and viruses do manage to break through the physical barriers, the body’s second line of defense, the immune system, will kick in. One very good feature of the immune system is its memory. The units of the immune system are the foot soldiers who keep us away from infections and they remember the bacteria or viruses that have attacked in the past so that if they return, the body is fully prepared to handle them.

The immune system consists of white blood cells such as neutrophils, monocytes, lymphocytes, eosinophils, and basophils. These white blood cells act as the second line of defense.

The immune system can be further divided into two parts:

  • Innate Immune System: This is what you are born with and what protects you as an infant. The cells that are a significant part of this system are called phagocytes.
  • Acquired Immune System: This develops as an extension of the innate system and with support from it. It recognizes new invaders and develops antibodies against them, thus adapting your bodies to keep diseases at bay.

Causes of Low Immunity

The immune system of our body can be affected by several external and internal factors that are responsible for low immunity. Some of the causes of low immunity include the following:

Lack of Micronutrients in Diet

Our body needs a wholesome and healthy diet that not only includes carbohydrates, proteins, and fat but also micronutrients such as vitamins and minerals. These vitamins include vitamin A, vitamin B, vitamin C, vitamin D, vitamin E, vitamin H, and vitamin K. Some essential minerals include calcium, iron, copper, magnesium, zinc, folic acid, and iodine. A lack of micronutrients may not be fatal in the short run or even in the long run, but studies have shown that they have a significant effect on the immune system.

Virtual male and female stopping microorganisms from attacking their immune system

Exposure to Harmful Substances

Excessive exposure to harmful substances such as pesticides, insecticides, chemical cleaning agents usually found at home, workplace, or industries, and even in chemically farmed food can all lower immunity. Smoking and alcohol are also some of the major substances that are known to decrease immunity to sickness and disease.


Toxins are produced in our own body during metabolism. If these accumulated toxins are not flushed out from the body, they can have a devastating effect on the immune system. Excessive toxin exposure can, in some cases, lead to poisoning of the bone marrow, which is known as the heart of the immune system.

Abuse of Antibiotics

Overuse of antibiotics is another reason for a decreased level of immunity in our body. Furthermore, bacteria can build resistance against antibiotics when used regularly. If resistant bacteria attack again, the immune system, as well as the antibiotics, will fail to curtail them and result in diseases.

Lack of Sleep

Lack of sleep is also known to be one of the causes of low immunity in a person. Studies conducted by Michael Irwin at the University of California have found that a lack of sleep causes modifications in the cytokine network. Cytokines are known to be immunological signaling molecules. The changes in the cytokine network cause cellular immunity to decline, thereby causing the immune system to weaken.

Excessive Workouts

General and sustainable workouts are recommended not only for developing overall health, but also for the benefit of the immunity system. However, as the saying goes, too much of anything is good for nothing, excessive workouts burn more oxygen in the body. Such excessive burning of oxygen produces free radicals, which attack the immune system cells and bring their numbers down. Although this can be cured with the help of consuming nutrient-rich food, the damage may not be fully repaired.

Intake of High Cholesterol Food

Intake of high cholesterol foods has also been found to be one of the major causes of low immunity. High levels of cholesterol slow down the process of natural defensive cells or macrophages that destroy infectious bacteria.


Stress releases hormones such as neuroendocrine hormones, particularly glucocorticoids and catecholamines. It has been observed that stress, through the action of such stress hormones, has damaging effects on immunity. Stress can have an adverse effect on natural killer cell activity, lymphocyte populations, and proliferation, as well as antibody production. It can also lead to a reactivation of latent viral infections. These effects may lead to severe consequences on the health, including slowed healing of wounds, and reduced responses to vaccines.

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About the Author

Prachee is a content writer for Organic Facts and is responsible for writing on the latest wellness trends. A former Journalism & Media teacher, she prides herself on being able to seamlessly dabble between health, science, and technology. She has completed her Masters in Communication Studies from the University of Pune, India and is currently pursuing an online course on “Introduction to Food and Health” from Stanford University, US. Prachee fancies herself to be a poet and a cook when the rare lightning of inspiration strikes.

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