What is an Immune System? A complete guide

What Is an Immune System?

The Immunity system is a complicated network of biological processes which protects your organisms from disease. Cells, tissues, organs, and the substances they produce that help together in the body’s defense against infections and other ailments. 

The immune system consists of thymus, spleen, tonsils, lymph nodes, lymph veins, and bone marrow and White blood cells.

Thymus, lymph nodes, spleen, lymph nodes, bone marrow and tonsils are the parts of our immune system.

How does the immune system work?

Your immune system protects you from chemicals that it considers to be dangerous or foreign. When viruses or bacteria are attacked and multiply, an infection occurs. As a result, the infection makes you sick. The infection is responsible for sickness.

By fighting against infections, your immune system defends you from sickness. When an antigen is detected by your immune system, it is assaulted. This is called  an immunological response . This response produces antibodies. Antibodies are proteins that bind to antigens in the body and attack, weaken, and remove them. Your body produces extra cells to resist the antigen.

Your immune system will recall the antigen, after that it will recognize the antigen if it is presented with it again. It will swiftly put out the appropriate antibodies, ensuring that you do not become ill. Immunity is a term used to describe a person’s ability to protect himself from a specific disease.

How many types of immune systems?

There are three different types of immunity system in human body such as :

Innate Immunity System : Everyone is born with a type of general defensive system, called the innate immunity system also known as natural immunity. It shields you against all antigens. Innate immunity is a set of defence that prevents hazardous substances from entering your body. In the immunological response, these barriers are the front line of protection.

Adaptive Immunity System : Adaptive immunity system is the second line force against non-self infection. Only vertebrates have adaptive immunity as well as acquired or specific immunity. The pathogen is a perfect match for the adaptive immune system. The adaptive immune response is designed to fight non-self infections, but it can also attack itself. As a result of this response autoimmune disorders can arise. 

Passive Immunity System (PIS) : Passive immunity refers to disease protection provided by antibodies produced outside the body. Passive immunity can be either natural or induced by the mother. It doesn’t require prior exposure to a disease agent, starts working  instantly, and lasts a long time.

Passive immunity from the mother is passed on to the child naturally. Antibodies are delivered through the placenta before the child is born to protect  against sickness.

Utilising different animals  or people,  antibodies provide artificial passive immunity. These antibody-containing preparations are referred to as antiserum.

Elements of the Immune system

The immune system consists of various components that work together to protect the body from outside invaders. The elements are given below:

White Blood Cells

White blood cells are the most important members of your immune system. They come from the bone marrow.They are also an element of the lymphatic system. 

Lymphocytes are  white blood cells that are part of the immune system. Lymphocytes are classified into two types such as  B cells and T cells.

B cells are important for facilitating the generation of antigen-specific immunoglobulin (Ig) directed against invading pathogens and are at the heart of the adaptive humoral immune system (typically known as antibodies).

T cells are a type of immune cell that directly targets foreign molecules.  Rather than attacking any antigen, T cells continue to flow until they come into contact with their particular antigen. As a result, T cells play a vital role to foreign substances in the immune system.

Lymphatic system

The lymphatic system is a complicated network of pipes that flows throughout the body. The lymphatic system’s major functions are to :

  • Control the body’s fluid levels.
  • In response to bacteria.
  • Take care of malignant cells.
  • Deal with cell products that would otherwise cause illness or disorder.

Part of the fats in our food are absorbed by the gut.

The lymphatic system is made up of the following components :

Microbes : Microbes are trapped in lymph nodes (also known as lymph glands).

Lymph veins : Lymph veins are pipes that carry lymph through your veins, which is a colorless fluid that bathes your body’s tissues and contains infection-fighting white blood cells. 
White blood cells are the cells that make up the body’s immune system (lymphocytes).


Antibodies are protective proteins also known as immunoglobulin that recognize  pathogens and the toxins (poisons) that are created by the immune system and aid in the fight against them. 

They search for antigens on the organism’s surface or in the molecules, they assault and subsequently expel them from the body. There are a lot of cells, proteins, and substances involved in this onslaught.

Antibodies can be found in blood, tissues, and bodily fluids. Plasma cells, which are formed from the immune system’s B cells, produce them. When a specific antigen binds to the antibody surfaces of B cells in the immune system, they become plasma cells.

Complement System

The complement system, commonly known as the complement cascade, is an immune system component that improves antibodies’ and phagocytic cells’ ability to remove infections and damaged cells from an organism, create inflammation, and assault the pathogen’s cell membrane..

The complement system is a combination of several small proteins found in the blood that the liver produces. In the normal course of things, they circulate as dormant precursors. 

When these small proteins are triggered by a trigger, proteases convert them into active cytokines. This sets off a chain of cleavages that releases more cytokines and the effect is amplified. The cytokines rupture the target’s phospholipid bilayer cell membrane, killing it in the event of an invading bacterium.

Complements are inactive versions of soluble proteins and glycoproteins found in serum. In serum, there are about 20 different types of complements.

The complements are  activated only during inflammatory responses. More compliments reach the infected tissue’s interstitial area through dilated blood arteries during inflammation, where they are activated by proteolytic cleavage.       


The spleen is positioned in the upper left corner of your abdomen, right behind your stomach and behind your diaphragm. It’s purple and plush, with notches on the upper front edge. It has the shape of a little spherical catcher’s mitt.

The spleen’s primary role is to filter your blood. It recognizes and destroys old, deformed, or damaged red blood cells.Red blood cells must go through a network of micro passages when blood circulates through your spleen, providing “quality control.”

Healthy blood cells easily pass through the spleen and circulate throughout the body. Macrophages in your spleen will break down blood cells that fail the test. Macrophages are huge white blood cells with the job of killing damaged red blood cells.

The spleen functions as a blood reserve organ as well. Blood channels in the human spleen can widen or contract depending on the body’s needs. Your spleen can retain up to a cup of reserve blood when its arteries are expanded.

Your spleen can respond by releasing reserve blood back into your system if you need extra blood for whatever reason, if you lose blood due to trauma for example.

Bone Marrow

The gelatinous substance  in the middle of the bones is called bone marrow. Bone marrow comes in two different colors, red and yellow. Blood stem cells can be transformed into red blood cells, white blood cells, or platelets in the red bone marrow.Yellow bone marrow contains stem cells that can turn into cartilage, fat, or bone cells and is mostly made up of fat.

Bone marrow is typically present in the ribs, vertebrae, sternum, and pelvic bones in mature individuals. In healthy adult humans, bone marrow accounts for about 5% of total body mass, therefore an individual weighing 73 kg (161 lbs) would have about 3.7 kg (8 lbs) of bone marrow.

In bone marrow diseases, both genetics and environmental factors play a role.Bone marrow abnormalities are diagnosed using blood and bone marrow testing. Depending on the condition and severity of illness, treatment options may vary. Bone marrow transplantation, blood transfusions and medicines are all options.

Vitamin C and D can help you grow more bone marrow stem cells. Vitamin C promotes the proliferation of our bone marrow stem cells (increase in numbers). Vitamin D3 can help our stem cells age more slowly, stay healthier, and specialize into different types of cells.


The thymus is a vital organ of the immune system, which serves as the body’s defensive mechanism, monitoring and protecting against a variety of viruses, cancers, antigens, and tissue damage mediators.

The thymus gland is situated behind the breastbone in the chest. It is responsible for the production of immune cells and so plays a vital role in the immune system. 

The organ’s main purpose is to mature T cells,(known  as T lymphocytes also). This is an infection-fighting kind of white blood cell. A variety of hormones are also produced by the thymus.

These cells are often donated to persons in need since they are so precious. According to a study published in the journal Cell, “it (the thymus) is the principal source of cells for the lymphatic system, much like bone marrow is for the cardiovascular system.”


The immune system protects the body from infection by forming a complex network of organs, cells, and proteins.

By keeping records of every germs (microbe) that has ever been defeated, so that the germs may be identified quickly and destroy them when they re-enter the body.

The immune system activates specialized and nonspecific immune responses in regard to invading infections and cancer cells.

Immunotherapy aims to boost these responses in order to stop cancer cells from spreading.

Furthermore, the immune system plays a very important function in protecting your body against potentially hazardous substances, infections, and cell disruptions.

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