What is the Immune System?

The immune system is the set of cells, tissues, organs, and processes of the body that work together to provide protection to our body against infection and toxins. Each of these elements plays a key role in the immune system function and preventing infection or disease, including cancer. The immune system is the body’s natural defense system.

Table of Contents

  1. What is the Immune System?
  2. Immune system function.
  3. Different Parts of the Immune System Function.
  4. When the immune system function working properly 
  5. When immune system function is not working properly
  6. Types of the Immune System Function


Immune System Function

In other words, the immune system’s function mainly is the body’s defense against foreign materials and biological agents such as bacteria, viruses, chemicals, and foreign cells and tissues. It also keeps a record of every germ it has ever overcome or killed so it can acknowledge that and destroy them quickly if it enters the body again. The immune system is the second most complex system in the human body whereas the nervous system is the first one. 

Immune System Function

  1. Fighting with microorganisms (such as bacteria, viruses, parasites, and fungi) and destroying them from the body to prevent us from getting infected.
  2. Acknowledge and wipe out harmful entities from the body.

The key to a healthy immune system function is its remarkable ability to distinguish between the body’s own cells called self and foreign cells called nonself. It can realize and remember millions of different enemies, and produce excretion and cells to match up with and destroy everyone through detailed and dynamic communications networks where millions of cells arrange into sets and subsets to pass information from side to side and all.

Different Parts of the Immune System Function

   The different parts of the Immune system function are:

  • White blood cells
  • Lymphatic system
  • Complement system
  • Antibodies
  • Spleen
  • Bone marrow
  • Tonsils
  • Skin

Each of these elements plays a key role in the immune system function and helps in preventing infection or disease.

1)White blood cells

White blood cells are the tycoon in our immune system function. They Serve as an army against harmful bacteria and viruses. Although they are only 1 percent in blood their effect is very powerful. They originate in the bone marrow but circulate in the whole body through blood and tissue and look for external attackers such as bacteria, viruses, parasites, and fungi which are unfavorable to our health. When white blood cells find anyone, they begin an immune attack and destroy the harmful substance.

There are five major types of white blood cells in the immune system function 






2)Lymphatic System 

The lymphatic system covers a vast network of thin tubes (lymph vessels)and lymph nodes that passes through our tissues to drain lymph fluid (a fluid containing infection-fighting white blood cells) from all over the body. It circulates in our body just like blood in other words, the lymphatic system is consist of

  1. lymph nodes or glands — which trap microbes
  2. lymph vessels –– tubes that carry lymph, the colorless fluid that contains infection-fighting white blood cells
  3. white blood cells (lymphocytes).

There are about 600 lymph nodes in the body. These nodes swell in response to infection, due to a build-up of lymph fluid, bacteria, or other organisms and immune system cells. The major parts of the lymph tissue are located in the bone marrow, spleen, thymus gland, lymph nodes, and tonsils.

the lymphatic system in the immune system function
  • Manage the fluid levels in the body
  • Forms part of the body’s immune system and fights against bacteria, other infections, and intruders.
  • Destroying old or abnormal cells, such as cancer cells
  • Absorb some of the fats in our diet from the intestine. 


An antibody, also known as an immunoglobulin, is a large Y-shaped protective protein produced mainly by plasma cells or B- cells and used by the immune system to identify and neutralize pathogens or foreign objects such as bacteria, viruses, and other chemicals. The antibody recognizes a unique molecule of the pathogen, called an antigen, via the fragment antigen-binding (Fab) variable region.

Antibodies in the Immune system function

Antibodies find antigens, stick to them, and identify for the immune system the exact type of antigen so that it can be destroyed. Each antibody is made for one and only one antigen, and it’s fitted with special receptors that will only bind to that antigen. For instance, a specific antibody is created to help destroy the chickenpox virus. Only that particular antibody will attack a chickenpox virus. Thus when an antigen is found in the body, the immune system’s function will create antibodies to mark the antigen for the body to destroy.

4)Complement System 

The complement system is made up of proteins that are produced mainly by the liver, circulate in the blood in an inactivated state till the system receives an appropriate signal for activation. The signal sets off a chemical chain reaction in which one activated complement protein triggers the activation of the next complement protein in the sequence and so on.

It’s a group of more than 30 proteins that work in a cascade to either kill germs directly or “mark” them or their location so that other cells can destroy them. They’re also part of cleaning up immune complexes, the antibodies attached to antigens.


The spleen is a blood-filtering organ that removes microbes and destroys old, worn out, or damaged red blood cells. It detects faulty red blood cells as well as any unwelcome micro-organisms (like bacteria or viruses) in blood. It is also an important organ in the immune system function, producing the white blood cells that fight infection and integrate antibodies. It also holds a reserve of blood.

6)Bone Marrow

Bone marrow is a spongy substance found in the center of the bones. There are two categories of bone marrow tissue: red marrow and yellow marrow. From birth to early adolescence, the majority of our bone marrow is red marrow which helps to produce blood cells. On average, bone marrow can generate hundreds of billions of new blood cells every day. As we grow and mature, increasing amounts of red marrow are replaced by yellow marrow and help to store fats.

Bone Marrow in the immune system function

Bone Marrow manufactures bone marrow stem cells and other substances, which in turn produce blood cells.

  • Red blood cells –These cells are red because they are filled with a protein called hemoglobin. It transports oxygen throughout the body
  • White blood cells – help the body fight against infection.
  • Platelets – Prevents excessive bleeding by helping blood to clot after an injury

The bone marrow is the producer of white blood cells which defend our bodies against infections.  Therefore, if the bone marrow does not produce white cells in adequate numbers, the body becomes at risk for infection.


The thymus filters and observe blood content. Before birth and throughout childhood, the thymus produces T-lymphocytes or T cells, a specific type of white blood cell that protects the body from viruses and infections. The thymus produces and secretes thymosin, a hormone necessary for T cell development and production. Once reach puberty, the thymus starts to slowly shrink and become replaced by fat.

8)Tonsils And Adenoids

Tonsils are small organs in the back of the throat. These small bumps at the back of the throat are the first level of defense in our function of the immune system. Due to their position at the throat they resist germs from entering the body through the mouth or the nose. They help prevent foreign bodies from reaching the lungs. Tonsils have the ability to filter microorganisms such as bacteria and viruses. Proteins called antibodies produced by the immune cells in the tonsils help to kill or destroy germs and help to block throat and lung infections.

Example-tonsils sample bacteria and viruses entering the body through the mouth or nose and flush them using lymph. 

Adenoids are two glands located in the roof of the mouth, behind the soft palate where the nose connects to the throat. They hang from the upper part of the back of the nasal cavity. They are covered by a layer of mucus and hairlike structures called cilia. The adenoids produce antibodies, or white blood cells, that help fight infections. They trap bacteria and viruses which we breathe in through our nose. They contain cells and antibodies of the immune system function to help prevent throat and lung infections.  


The skin is the body’s largest organ and serves as a protective barrier that defends against pathogens and toxins. It also possesses its own immune cells and lymphatic vessels.

When the immune system function working properly 

it can easily detect a difference between the body’s own healthy cells and foreign cells or which substances are foreign to the body. It activates, is ready for action, attacks, and kills foreign invader microbes that can cause harm.

If anyhow germs or foreign bodies succeed to get into our body then the immune system function notices it and give rise to the release of special cells which travel to the trouble area, attack the attacker and eliminate it from our body. Every cell has its own tag which helps our body to know if the cell is familiar or not. When a foreign cell (antigen) enters the body it is quickly detected and several types of cells then work together to identify whether it is a threat to the body. If it is, then antibodies (specialized proteins) are produced. They lock onto these antigens and then work with other cells to destroy them. If the body isn’t able to destroy the antigens straight away then the germs will multiply and cause illness. But, as our body destroys more of the germs we start to feel better.

Once produced these antibodies stay in a person’s body for life, meaning if those germs enter the body again we will be able to quickly identify them and destroy them.

Example of the Immune System function

chickenpox disease catches on once only, as the body has a chickenpox antibody stocked, which is waiting to kill the microbes of chickenpox if it will hit the body again. Thus once an antibody has been formed, a copy is leftover in the body so that if the same antigen arrives another time, it can be treated instantly.

An example of this concept occurs when we get a vaccine. our immune system builds up antibodies to the foreign cells it finds in the vaccine and will quickly remember these foreign cells and destroy them if we are exposed to them in the future.

When immune system function is not working properly

When this happens, we can feel sick, diminish, and have a hard time fighting off the illness. When the immune system is not able to destroy attackers, infection develops. Sometimes our immune system rise an attack when there is no attacker or doesn’t stop an attack after the enemies have been killed.

There are four types of function of the immune system disorders occur:

  1. Immunodeficiency disorders – disturb the body’s ability to defend itself against antigens.
  2. Autoimmune disorders –  An autoimmune disorder is where the immune system mistakenly attacks the body’s healthy cells as though they are germs and destroys healthy body tissue. Therefore it triggers inflammation in the body. For example, IBD is an autoimmune disorder
  3. Allergic disorders – a hypersensitive reaction to an irritant that has no effect on most people e.g. pollen, nuts
  4. Cancers of the immune system – For example lymphoma


Types of the Immune System Function

There are three types of Immune System function in the human body 

  • The Innate Immune System
  • The Adaptive (acquired) Immune System
  • The Passive Immune System


1)Innate Immune System –– 

We are born with an innate immune system. It is the first line of safeguarding opposed to pathogens also called general protection from attackers. It is genetic and is active from childbirth. When the innate system became aware of an intruder, come into action at once or within hours, enclose and absorb the raider and killed it inside the immune system cells called phagocytes.

The innate immune system consists of :

Natural blockade – the skin acts as a barrier to block germs from entering the body, the gastrointestinal tract, the respiratory tract, the nasopharynx, cilia, eyelashes, and other body hair.

Protection system– secretions, mucous, bile, gastric acid, saliva, tears, and sweat.

2)The Adaptive (acquired) Immune System — 

Adaptive (active) immunity promote throughout our lives. We develop an adaptive immune system when we are exposed to diseases or get vaccinated.

we are caught to millions of likely pathogens daily, over contact, ingestion, and inhalation. With help from the innate system, the adaptive immune system produces cells (antibodies) to protect the body from a specific attacker. Through this process, the body builds up a library of antibodies to different pathogens and remembers previously coming across specific pathogens and damaging them when they attack again. 

3)The Passive Immune System  —

The Passive Immune System is produced in one person antibodies by transfer from another person. It can be provided when a person cannot able to make antibodies of their own, to fight against infection.

Example- 1)Infants receive when their mothers’ antibodies and pathogen-fighting white cells cross the placenta to reach the developing children before birth.

2)Antibodies and protection rich Colostrum, which an infant receives during nursing sessions in the first days after birth.

3)Antibodies contain breast milk that passes to the nursing infant. 


Thus our immune system function is essential for our survival and keeps us healthy. Without an immune system function, we would have no way to fight harmful things that enter our body from the outside and as a result, our bodies would be open to explosions from bacteria, viruses, parasites, etc.

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