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The immune system is a complex network of cells and organs that defend the body against infection.

The main parts of the immune system are:

- white blood cells

- antibodies

- complement system

- lymphatic system

- spleen

- bone marrow

- thymus


You can hear and feel the beating of your heart, so you know it’s working. The immune system, however, is silent.

Even though we are much less aware of our immune system, it is at work 24/7 protecting us from thousands of potentially deadly attacks every day.

Let’s examine the different lines of defense used by the immune system to protect us.


The first line of defense is known as innate immunity. This is a range of protective mechanisms we are all born with.

The innate immune system provides nonspecific protection against various pathogens such as viruses, bacteria, fungi, protozoans, and worms.

A number of defense mechanisms serve the innate immune system, which includes physical barriers such as the skin, chemical barriers such as antimicrobial proteins that harm or destroy invaders, and cells that attack foreign cells and body cells harboring infectious agents.

Before moving on to the second line of defense, let’s delve a little deeper into the defense mechanisms of innate immunity.


The skin is an external barrier made from layers of cells serving as a protective barrier to infection. Not only does skin provide a protective barrier to keep invaders out, but it also secretes fatty acids and enzymes.

The fatty acid, oleic acid, can kill certain bacteria while the enzyme lysozyme, can break down the outer wall of certain bacteria.

Internally, mucous membrane linings of the respiratory, gastrointestinal, and genitourinary tracts provide a protective barrier of cells that are constantly being renewed. The membrane traps small particles to prevent them

from attaching to cells.

Another crucial aspect of innate immunity is chemical barriers to infection.

When microbes penetrate the body’s protective barriers and enter the internal tissues, they encounter a variety of chemical substances that attempt to prevent their growth.

There are many mechanisms and cells by which chemicals work to harm or destroy invaders. These processes go beyond the scope of what we can discuss here, just know that they are continually on the lookout for foreign invaders and ready to strike at any time.


Many of you are familiar with this response but may have only heard of the dangers it can pose: inflammation.

Inflammation can eliminate infection or hold it in check until specific, acquired immune responses have time to develop.

Infection often results in tissue damage, which may trigger an inflammatory response. The signs of inflammation include pain, swelling, redness, and fever, which are induced by chemicals released by macrophages. (cells that eat foreign bodies)

Inflammation is a healthy protective immune response. However, when chronic inflammation exists in the body, chronic disease develops.


The second line of defense is called acquired immunity.

Acquired is named as such because you are not born with this form of immunity; it is acquired through exposure to pathogens.

This line of defense is acquired from:

- exposure to an infection or disease

- another person’s antibodies


It is well-established that persons who contract certain diseases and survive generally do not catch those illnesses again. This is made possible through the mechanisms of acquired immunity. When your immune system is

exposed to a pathogen, it learns to recognize it and can make your immune system better equipped to fight off that type of germ the next time you’re exposed to it.

Acquired immunity is dependent on the specialized white blood cells known as lymphocytes. Lymphocytes are the cells responsible for the body’s ability to distinguish and react to an almost infinite number of different

foreign substances.


Lymphocytes originate from stem cells in the bone marrow and can travel and multiply in response to appropriate stimulation.

If you’ve heard the terms T Cells or B Cells, these are referring to different types of lymphocytes. Both T and B cells recognize and help eliminate foreign molecules, but they do so in different ways.


Lymphocytes are distinguished from other cells by their capacity to recognize foreign molecules by means of receptor molecules.

A receptor molecule is a special protein whose shape is designed to fit foreign molecules. Think of these molecules as a key that fits into a lock.

Any foreign material that binds specifically to a receptor molecule is called an antigen. Antigens include molecules found on invading microorganisms, such as viruses, bacteria, protozoans, and fungi, as well as molecules

located on the surface of foreign substances, such as pollen, dust, or transplanted tissue.

Certain antigens can induce an immune response when they bind to a receptor molecule.


One of the many incredible abilities of the immune system is that it keeps a record of every microbe it has ever defeated. This enables the immune system to recognize and destroy the microbe quickly if it enters the body again before it can multiply and make you feel sick.

However, some infections, like the flu and the common cold, have to be fought many times because so many different viruses or strains of the same type of virus can cause these illnesses and the same symptoms.

Therefore, catching a cold or flu from one virus does not give you immunity against the others.

What we are exposed to, dictates our acquired immunity. For example, where we live, and our exposure to different environmental conditions all impact our ability to fight off various diseases.

If you’ve ever experienced allergies when visiting someplace for the first time, this is due to the exposure of something your system is not already familiar with. Next time you visit, you may not have the same reaction for which you can thank acquired immunity.


Because we are all exposed to different pathogens, we all have unique immune defenses. This means immune systems vary from person to person.

While we all have similar innate responses, such as a skin barrier, our acquired immunity can be vastly different. In fact, recent studies have found that our history and environment—like where and with whom we live—are

responsible for 60% to 80% of the differences between individual immune systems, while genetics account for the rest.


An overactive immune system can result in a number of conditions, including allergies and autoimmune diseases.

Allergic diseases include allergies to foods, medications, or stinging insects, anaphylaxis, hay fever, sinus infections, asthma, hives, dermatitis, and eczema. These conditions result when the immune system makes an

overly strong response to allergens.

Autoimmune diseases include multiple sclerosis, autoimmune thyroid disease, type 1 diabetes, systemic lupus erythematosus, rheumatoid arthritis, and systemic vasculitis. When the immune system mounts a response against normal components of the body, autoimmune disease is to blame.

An underactive immune system, also known as immunodeficiency, does not function correctly and makes people vulnerable to infections. It can be life-threatening in severe cases.

Immunodeficiency can be inherited and include conditions such as common variable immunodeficiency (CVID), x-linked severe combined immunodeficiency (SCID), and complement deficiencies.

Immunodeficiency can also arise as a result of medical treatment or be caused by another disease, such as HIV/AIDS or certain types of cancer.

Now that you have a more in-depth understanding of the immune system and how it works to protect us, let's take a look at ways to strengthen your immune system!

The ability to boost immune function is complex and continually under study. This is due to the fact that the immune system is a system. It requires balance and harmony among its parts. The interconnectedness of the

immune response is very complex.



So let’s take a look at the effects of lifestyle being researched to give your immune system a boost.

Your first defense is to live a healthy lifestyle. Not only will your immune system benefit, but every part of your body will function better by following the following tips:

- Don't smoke.

- Eat a diet high in fruits and vegetables.

- Exercise regularly.

- Maintain a healthy weight.

- If you drink alcohol, drink only in moderation.

- Get adequate sleep.

- Take steps to avoid infection, such as washing your hands frequently.

- Try to minimize stress.


It has been well established that people who are malnourished are more vulnerable to infectious diseases.

Another group of individuals who are susceptible to micronutrient malnutrition is the elderly. This is because older people tend to eat less and often have less variety in their diets.

Micronutrient deficiencies—for example, deficiencies of zinc, selenium, iron, copper, folic acid, and vitamins A, B6, C, and E—may alter immune responses.

If you suspect your diet is not providing you with all your micronutrient needs, taking a daily multivitamin and mineral supplement may help increase the power of your immune system.


Chronic stress is common in today's society. Our busy schedules and packed social calendars demand more from us than any other time in history. Other stressors, such as financial burdens and anxiety all contribute to

chronic stress.

When we experience stress, hormones are released in the body. However, when under constant stress, these hormones remain present throughout the day.

The result of chronic stress leads to a never-ending list of diseases and illnesses, ranging from depression to heart attack. During times of stress, the immune system may also be inhibited. Therefore, regularly participating in stress-reducing activities is not only beneficial to overall health but general immunity as well.

References and ReSources:

How the flu works:

How to boost your immune system:

Videos on immunity:

Take practical steps to help the immune system

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