Understanding Your Immune System – Structure, Functions, and Disorders


Your immune system is significant to your entire health. It is a system that enables other body systems to operate in a healthy environment.

Why are some people prone to diseases while others enjoy an extended healthy life? It is all about your immune system. The strength of your immune system determines your health.

In your daily activities, you encounter disease-causing pathogens such as viruses, bacteria, allergens, and others. If your immune system is weak, it cannot defend you from the invading pathogens. You need a healthy and complete immune system to protect and shield you against such health enemies.

Immune System Definition

What is the immune system? The immune system is a network of body structures and processes that defend your body against diseases. The system involves some cells, tissues, and molecules for the total defense mechanisms.

The immune system cells are produced in the bone marrow. Through the lymphatic system and the circulation system, the cells move to defend the peripheral tissue against pathogens.

Types of Immune System

You have two major types of immunity in your body, which are innate and adaptive. Learn more about these two types of immune systems:

Innate immunity

The innate immunity is nonspecific. It responds immediately against any non-self or foreign substance. This type of immune system is available to a newborn child through inheritance from the parents. The innate immunity acts as a first-line physical barrier against pathogens and other foreign particles.

The defense process of the innate immune system include:

Barriers - skin, eyelashes, and nasal hairs (cilia)

Mechanisms – Secretions of mucus in the throat and gut, gastric acid, bile, tears, and saliva.

Immunological responses – The immune system causes inflammation by sending immune cells to the infected site. The response increases blood flow. It is a complement response that marks the enemy for attack and destruction. If the strength of the pathogen resists the innate immunity and gets through the first line barrier, the adaptive immunity comes into effect.

Adaptive Immunity

Adaptive immunity, which is also called the acquired immunity is an immune type that develops through exposure to pathogens. Your body adapts the protection once you successfully recover from an infection or disease attack. The adaptive immunity enhances its immune response through a previous successful response from the same pathogen.

The acquired immunity uses B-cells and T-cells to function in its process. The bone marrow produces both cell types. The B-cells mature in the bone marrow and then migrate into the lymphatic system. After the production of the T-cells, they immediately migrate to the thymus for maturity.

However, the adaptive immune system response towards any attack is slower compared to innate immunity.

Immune System Parts

The entire immune system structure involves various parts such as body organs, proteins, tissues, cells, and mechanisms to keep you healthy.

The significant parts of your immune system include:

The Skin

Skin is the foremost body protection against pathogens. While the skin layers are the barriers against microbes' attacks, the cells of the skin contain some immune cells with antimicrobial proteins. Not all skin layers contain protective cells, but only some skin layers can produce antimicrobial proteins.

Skin enforcement, together with the mucous membranes such as in bronchi and the gut wall lining, reduces your risk of pathogen attacks.

White Blood Cells

Your blood contains some red cells, white cells, plasma, and platelets. The white blood cells are a section of the immune system in your body. These cells, which are also called leukocytes, play a significant role in protecting you against pathogen invasion.

The level of white blood cells in a healthy person should be between 4,500 and 11,000 per cubic mm of blood, which translates to about 1%. However, the level of white blood cells is not standard, and it can vary between a male and a female adult.

There are different types of white blood cells according to their specific roles in the immune system. These are:

Lymphocytes – The lymphocytes are responsible for making antibodies useful for body defense. The antibodies strengthen the defense mechanism to stand against threats like bacteria and viruses.

The source of lymphocytes is your bone marrow. Your spleen, lymph nodes, and thymus gland also produce other types of lymphocytes to boost the immune system. The cells then enter into your blood for circulation. Other cells get into the lymphatic system to protect you from infections.

The lymphocytes have two types of cells, which are T-cells and B-cells. The T-lymphocytes directly attack and destroy infected cells and cancer cells. The B-cells make antibodies that adapt to the antigen to destroy them.

Neutrophils – It's a dominant type of white blood cell that accounts for approximately 55% to 70% of the white blood cells. Neutrophils respond and intercept a threat immediately.

Basophils – The role of this type of white blood cells is to protect you against parasitic infections. Basophils also intercept allergic reactions by producing histamine and also to produce blood-thinning compounds that prevent blood clotting.

Eosinophils – from the bone marrow where the eosinophils cells are created, they recruit themselves to different body tissues as new locations. One of the roles eosinophils play is to defend their host against infections.

Eosinophils also respond quickly against allergic reactions and parasitic infections. The white blood cell type also promotes inflammation in an infected area to control the disease.

Monocytes – Monocytes are the most significant type of white blood cells compared to the other four types of white blood cells. They settle in your blood and body tissues after release from the bone marrow, which is their source. Monocytes play a crucial role in blocking and defending you against microbes. They fight off viruses, bacteria, fungi, and other harmful substances.

Innate vs Adaptive Immune Players

The Antibody

An antibody, which is also known as an immunoglobulin, is an immune system protective protein. The antibodies recognize any harmful foreign substances such as bacteria and other toxic substances.

The antigens in the body trigger B-cells to action, which then binds to the antigen to produce the plasma cells. The plasma cells then create an antibody matching the particular antigen. The antibody begins to multiply and mature to resemble their 'mother' cell. The duplicate cells are known as the clones.

The plasma cells produce and secrete antibodies in millions into the lymphatic system and the bloodstream. The antibodies then move on a rampage, ready to identify and attach to the antigens.

The antibodies then attach to the pathogens to prevent attaching and infecting the healthy body cells. After marking the harmful substances, the antibodies activate the T-cells into action against the marked pathogen to attack and destroy it.

The production of antibodies continues until the infection clears.

The Antibody Structure

An antibody has a 'Y' shape. It consists of two heavy chains made of amino acids joined by polypeptide (peptide bonds) at the neck of the 'Y' and two light chains. The chains have antigen-binding tips.

Immunoglobulin Classes

The antibodies have five immunoglobulin classes according to their activities in the immune system. The five types are IgG, IgM, IgA, IgD, IgE.

The Lymphatic System

The lymphatic system is one part of the immune system and another part circulatory system. The primary immune functions of the lymphatic system are:

  • Filtering bacteria and other pathogens from body tissue by the lymph nodes
  • Dealing with cancer cells
  • Removing dead cells and cell products that could be harmful to the body

The lymphatic system consists of lymph and lymph vessels similar to the vessels of the circulatory system.


Lymph is a clear fluid containing pathogen-fighting white blood cells or lymphocytes that circulate through the lymphatic system and in the body. The blood plasmas from the blood vessels enter the spaces between body tissue to become interstitial fluid or tissue fluid. The fluid from the tissue then enters the lymphatic system by lymph vessels to become lymph carrying some foreign substances.

You can't then be wrong to say that the lymph is the tissue-bathing fluid that carries away any foreign substances for filtration.

Lymph Vessels. Lymph vessels are the means of transporting lymph throughout the lymphatic system.

Lymphoid Organs. The production of most lymphocytes, maturation, and differentiation takes place in the lymphoid organs. The lymphocytes then migrate to other parts of the body and in the lymphatic system.

The lymphatic organs are divided into two sections, the primary lymphoid organs, and the secondary lymphoid organs.

Primary Lymphoid Organs

The primary lymphoid organs are the sites for lymphocyte formation and development, a process known as lymphopoiesis. The primary lymphoid organs consist of:

Bone Marrow – Bone marrow is spongy-like tissue found inside your bones. There are two different types of bone marrow in your bones. The red and the yellow bone marrow.

Our interest, in this case, is in the red bone marrow that produces blood cells. The stem cells in the bone marrow produce white blood cells. The cells then divide into B-cells and T-cells. The T-cells then migrate into the thymus for further development and maturation while the B-cells continue to develop and mature.

The B-cells then move to other parts of the body through the circulatory system in search of pathogens to destroy them. The matured T-cells also join forces with B-cells in your protection against pathogens and other invaders.

Thymus – The thymus is a crucial gland in the glandular system. Read more on the glandular system.

It secretes thymosin hormone essential for T-cells growth. You have thymus in the thoracic cavity mediastinum, at the front of the heart, and back of the sternum.

As mentioned earlier, the T-cells move from the bone marrow to settle in the thymus. The thymus is the development environment for T-cells. That is why they are called T-cells, where "T" stands for thymus. Thymus regulates T-cell development, which occurs in the cortical and medullary areas of the thymus.

The epithelial cells in the thymus cortex present antigens to the maturing T-cells to test their response. Some of the T-cells overcome the antigens and survive while others die. The matured T-cells that survived then transfer to the medulla part of the thymus for later use against invading pathogens.

The Secondary Lymphoid Organs

The secondary lymphoid organs (SLOs) initiate the development of lymphocyte to maturation, survival and finally, activation.

The secondary lymphoid organs include the following:

Spleen – The spleen is above the abdomen on the far left side. The primary function of the spleen is to filter out pathogens or microbes from the red blood cells and to store leukocytes. Its role also is to destroy damaged red blood cells and recycle the old ones.

The organ is the storage of white blood cells and hence defending the body against bacterial attacks such as meningitis and pneumonia-causing bacteria.

Lymph Nodes – Lymph nodes are small glandular organs mainly located in the adenoids, tonsils, neck, armpits, groin, and mediastinum. The glands filter pathogens and foreign substances in the lymph coming from the body tissues. The macrophages then digest the filtered substances, a process called phagocytosis. Macrophages are monocytes-like standby cells that perform immune functions in the lymphatic system at the infection sites.

Peyer's Patches – The Peyer's patches are some small masses found in the ileum in the small intestine. They are more like the lymph nodes and is the reason they are also called aggregated lymphoid nodules.

The aggregated lymphoid nodules of the digestive system are found in the mucosa area of the ileum and can also spread to the submucosa area. For such a reason, they are called mucosa-associated lymphoid tissue or MALT.

They are the defense mechanism of the gut against microorganisms such as harmful intestinal bacteria. These aggregated lymphoid nodules also keep watch on the population growth of the gut bacteria as a role in the immune system. The lymphocyte cells in the Peyer's patches are the T-cells, a few B-cells, and macrophages.

Mucosal Tissue – The mucosal tissues are the barriers to pathogens when entering the body from outside. The mucosal membrane contains some immune cells of the innate and adaptive immune systems. The infection-causing agents cannot enter the body through mucosal tissues before encountering stiff immune defense.

Some mucosal tissues, such as the small intestine and the respiratory tract, contain some immune cells in the mucus (protective fluid). The thick fluid form a barrier against dust and pathogens entrance to the body.

The Complement System – The complement system is another part of the immune system. It involves a series of proteins that circulate in the tissue fluids and the blood. The proteins have a regulated way of interacting with one another. The proteins, which are ordinarily dormant, become active in response to pathogens. They activate one another enzymatically by cleaving to the next protein in the series. The proteins in the cascade interact with each other to attack and eliminate pathogens.

Peyer’s Patches, “Tonsils of the Intestine”. Found in the wall of the small intestine, they capture and destroy bacteria.

Immune System Disorders

"What happens if your defense weakens?" You may wonder! Your immune system is your natural defense.

The immune system, like any other body system, is vulnerable to weakening or exhaustion. It is, therefore, essential to educate yourself and become aware of the disorders that can result in low immunity.

The immune system disorders can be divided into three classes, immunodeficiency, autoimmunity, hypersensitivity.

Immunodeficiency Disorders

Immunodeficiency means low immunity. Immunodeficiency disorders have two types. Whether it is primary immunodeficiency or secondary, the effect is a variety of diseases. The primary immunodeficiency is an inborn disorder, and secondary is acquired or adapted immunity, which occurs after birth.

Two common immunodeficiency disorders are:

Acquired Immunodeficiency Syndrome (AIDS)

AIDS is an adaptive immune system disease caused by HIV (human immunodeficiency virus). The virus attacks T-cells, CD4s of lymphocytes in the immune system. With low CD4s, you become exposed to other infections.

Severe Combined Immunodeficiency (SCID)

A severe combined immunodeficiency, also known by its nickname 'bubble boy or bubble baby' disease, is a primary immunodeficiency disease. (Read the Bubble boy – David Vetter story here). The type of immunodeficiency disorder is present at birth and results in weak immunity to a newborn child.

The condition is a genetic defect that affects the formation of T-cells in the bone marrow. To some children, the disease can affect the B-cells and NK-cells (natural killer cells) and hence exposing the child to various life-threatening infections.

Autoimmune Disorders

The autoimmune disease is when your immune system mistakenly begins attacking your organs and tissues instead of attacking bacteria, viruses, and other pathogens. A healthy immune system should differentiate your organs and tissues from foreign substances.

Some of the autoimmune diseases are:

Rheumatoid Arthritis

Rheumatoid arthritis is an inflammation-causing disease. The disease mostly affects the joints, starting with small joints of the hands and feet. As chronic inflammation degenerates, it affects other joints such as knees, hips, and shoulders.

Common symptoms of rheumatoid arthritis are abnormal joint inflammation and stiff joints, especially finger joints.

Immune Thrombocytopenia

Immune thrombocytopenia is an autoimmune disorder. The antibodies in the immune system begin to attack and destroy the normal blood platelets to leave you with low platelets in the body. The immune system can also damage your bone marrow cells and hence affect immune cell formation.

Without enough platelets, you become prone to non-stop bleeding. Platelets respond to bleeding after injury by causing blood to clot.

Type 1 Diabetes

With type 1 diabetes, the pancreas, which is the source of insulin, fails to produce insulin. Type 1 diabetes is an autoimmune disease. The immune system mistakenly turns against healthy pancreas cells to destroy them.

Hypersensitivity Reactions

Hypersensitivity reaction (HR) is an abnormal or exaggerated immune response towards allergen or pathogen. There are four types of hypersensitivity reactions:

Type 1: Immediate hypersensitivity – It is an immediate anaphylactic-like allergic reaction against foreign substances such as pollen, dust, and pet fur.

Type 2: Cytotoxic Reaction or antibody-dependent – This type of condition is an allergic reaction where the antibodies destroy body cells. You can refer to this hypersensitivity as an antibody-mediated process. Some types of antibodies can attack your body's cells, such as red blood cell membrane mistaking to be allergens.

Type 3: Immune Complex Reaction – The hypersensitivity can happen due to some immune complexes in the body tissues. Immune complexes are when your immune system produces a large number of antibodies to attack antigenic determinants known as an epitope. It gets worse when antibodies settle on the tissue or organ surfaces such as the spleen or liver.

The macrophages ignore consuming such antibodies due to their location in the tissue. The enzymes in the tissue or organ where the complex antibodies settled then attempt to break them down in the digestion process.

The procedure then triggers inflammation to the tissue concerned. Also, the presence of immune complexes in tissues or organs can result in immune complex or autoimmune disorders.

Type 4: Hypersensitivity – It is the cells mediated reaction by the immune system, which is also called delayed hypersensitivity. In this condition, the antigens are bound to the T-cells instead of the antibodies. Unlike with the antibodies, the T-cells take time to react to the antigen, which results in delayed hypersensitivity.

Hypersensitivity Disorders

Hypersensitivity is a health condition that can lead to other disorders. Some of the hypersensitivity diseases are:

Bronchial Asthma

Bronchial asthma is a chronic airway inflammatory disease caused by hypersensitive reactions. The disorder can lead to breathlessness, wheezing, coughing, and chest tightness. The reactions become severe early in the morning or in the night.


Anaphylaxis is an acute hypersensitivity reaction that can lead to respiratory failure. The IgE antibodies, in this case, mount up excess histamine and leukotriene to overcome the allergens. The rapid over-response reaction can result in severe allergic reactions causing anaphylaxis.

Some of the anaphylaxis symptoms are shortness of breath, tongue or throat swelling, vomiting, low blood pressure, and itchy rash.

Celiac Disease

Celiac disease is a gluten-sensitive disorder of the intestines. The hypersensitive condition is an immune reaction against gluten. Gluten is wheat, barley, and rye protein. The condition damages the small intestine lining, which then affects nutrient absorption.

IBD (Inflammation of the Bowel Disease)

IBD is a name of two conditions, ulcerative colitis and Chrohn's disease. Both are immune system diseases that lead to chronic digestive inflammation.

Ulcerative colitis can cause chronic ulcers or inflammation and sores to the innermost large intestine and rectum linings. While Crohn's disease is inflammation of the digestive tract lining and which can extend further into the underlying tissue.

Bottom Line

For an immune system to remain healthy, you must take responsibility to ensure you eat a healthy diet. Steer away to lifestyles that can affect your immune system, such as excessive alcohol intake or smoking. Remember to keep fit by exercising regularly.

You can also help your immune system to remember past infections, what might have led to such conditions, and how the system overcame them. For instance, you don't have to subject your immune system to allergic diseases if you can remember what causes the allergy. You can then avoid anything that triggers your sensitivity.

Avoid compromising your immune system to unhealthy exposures. Just like you, your immune cells are prone to exhaustion. Help your immune system remain active and healthy by staying away from toxic environments or avoiding unhealthy and unhygienic lifestyles.

Do you have a question on immune system condition or any other subject about your health? With Island Healthworks Natural Clinic, you are at the right place to get your answers. You can have your blood analyzed to know the condition of your immune system. 

Yvonne Dollard Perc: Owner of Island Healthworks, Natural Health Practitioner, Teacher, Writer and Editor.
Elizabeth Njuguna: Researcher, Freelance Writer, with a Focus on Natural Health.
Sherry Robb: Print, Web and Social Media Designer specializing in the natural health and fitness industries.

To learn more, contact Yvonne Dollard Perc at Island Healthworks. Yvonne offers phone consultations where she will develop an individualized health care program and lifestyle plan tailored to your specific needs through a personal health and lifestyle analysis.

Call 250-468-7685 to speak with Yvonne and set up a phone consultation!

Yvonne offers in-person consultations with assessment of your specific needs, health and lifestyle coaching, and the best of integrative natural health care. To book your in person consultation, please call 250-468-7685!

This article is intended for educational purposes and the information contained within is not intended to treat, diagnose or cure any disease or health problem. Please seek appropriate medical attention for any health complaints. We cannot take responsibility for your health care decisions. Our intent is only to offer health information to help you with your search for better health. 

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Friday, 14 August 2020