Immune system

The immune system is a system which is made up of special cells, tissues, and proteins that defend us against germ and microorganisms. The immune system performs a great job of keeping people safe from infections.

This system makes the defense system of the body against the infectious microorganisms. Through the immune response, the immune system attacks organisms that invade body systems.

The immune system consists of a network of cells and tissues that works together and protects the body. The cells which are involved in the immune response are mainly white blood cells also known as leukocytes.

These cells are produced in the spleen,  thymus, and bone marrow.


Cells of the immune system


White blood cells circulate in the blood vessels and in lymphatic vessels. These cells are on constant patrol and search for foreign particles. When these cells find a target they send signals to others and start multiplying.

There are two main types of white blood cells.

1.  Phagocytes

These are the type of white blood cells which surrounds and absorb pathogens and then digest these pathogens with the help of various enzymes. Phagocytes are of many types which are

I. Neutrophils– a common type of phagocytes that attacks bacteria.

II. Monocytes– these cells have many functions.

III. Macrophages- these cells remove dead cells.

IV. Mast cells– these cells also have many functions such as wound healing etc.

2.  Lymphocytes

These cells remember previous attacks and recognize the attacks if they are by the previous invaders. The life of these cells starts in the bone marrow. Some cells stay in the bone marrow while others move to the thymus.

The cells which stay in bone marrow develop into B lymphocytes while the cell that moves into the thymus developed into T lymphocytes.

I. B lymphocytes– these cells produce antibodies and alert T cells.

II. T lymphocytes
They destroy the harmful cells and activate other leukocytes.

How does this system work?

The actions of the immune system begin when a foreign substance enters the body.  As the substance enters there is a group of cells that recognize them and respond.

These cells then activate B lymphocytes to produce antibodies. Antibodies are specialized proteins.

These antibodies stay in the body and protect the body in the future.

Antibodies recognize antigens and lock onto it but antibodies are not capable to destroy the antigen. The process of destroying antigens is done by the killer T cells which are activated either by antibodies or by damaged cells.

Another group of T cells sends signals to other cells to do their jobs.


The protection against the harmful pathogens provided by the immune system is known as immunity. The immune is different in persons but in general, it becomes stronger in adulthood.

There are three types of immunity which are

1.  Innate immunity
2.  Adaptive immunity
3.   Passive immunity

Innate immunity

The innate response occurs when pathogens are identified by pattern recognition receptors.  Every person born with innate immunity.  Innate immunity includes external barriers such as mucous membranes and skin.

Adaptive immunity

Adaptive immunity develops throughout our lives when the body from various diseases. Adaptive immunity consists of lymphocytes.

Passive immunity

This type of immunity is borrowed from another source and it lasts for a short period of time.

Example of passive immunity is antibodies present in breast milk.


This is a process in which antigens or weakened pathogens are introduced to a person in such a way that these pathogens do not make him sick but activate their immune system to produce antibodies. These antibodies stay in the body and protect the body from diseases for which they are immunized.

Immune system diseases

The immune system has a very complex structure and works through very complex mechanisms. Sometimes, the mechanisms of the system are disturbed and malfunction starts.

The disorder of the immune system are divided into three types which are
1.  Immunodeficiency
2.  Autoimmunity
3.  Hypersensitivity


These types of disorders occur when one or more parts of the immune system do not function.

In some cases, these disorders can be inherited.



In this type of disorder, the immune system mistakenly attacks the body healthy cells. In this type of disorders, the body is not capable to distinguish foreign and body cell.

1. Celia diseases
2. Type 1 diabetes
3. Graves disease
4.  Rheumatoid arthritis


In this type of disorders, the system overreacts in such a way that it damages healthy tissues of the body

Anaphylactic shock

The immune system is vital and very important for the body to protect itself from the germs and microorganisms but there are also other system and organs which also helps the body to fight against the disease.