Immune System

The immune system is a very important part of our body. The immune system helps us by protecting our body against diseases which are called pathogens.

These pathogens include things such as bacteria, viruses and parasites and the immune system is made up of different organs, tissues and cells that help to fight off harmful pathogens.

The body has specific and non specific immunity. Specific immunity means that the body uses white blood cells to fight antigens and microbes.

Non-specific immunity is when the body protects itself against harmful materials that go into the body. With non-specific immunity, the body fights off viruses and bacteria.

Part of the Immune System

There are many organs that help with the immune system and these include the lymph nodes, bone marrow, spleen and thymus.

The cells that make up our body’s immune system circulate in the blood to fight off diseases and they are also found in different organs and tissues such as in the bone marrow, the lymph nodes, spleen, tonsils and even in the small intestine.

All living things can be attacked by viruses and bacteria, and multicellular animals and humans have cells that are made to deal with infection that comes in the body, this is part of the immune system’s job.

The human immune system is powerful, and it is the way that our body survives because the world has an countless amount of bacteria, even a million bacteria could fit on the tip of a needle.

These bacteria are only seen by a microscope.

Disease Causing Pathogens

The immune system has cells that help destroy microbes that are disease causing pathogens. A microbe is so small that it can only be seen with a microscope.

Some of the cells in the immune system are used to fight certain kinds of diseases and then other parts of the body helps these cells to fight the diseases.

When pathogens enter into the body, infection can happen, and it can happen quickly.

The body will either get rid of the infection by fighting it, or the infection will happen and can cause a disease.

Most diseases happen hen the body’s immunity is low or if it is not as strong as it should be.

Symptoms of Diseases

Symptoms of diseases can be different depending on what pathogen is in the body.

Some symptoms include a fever, a rash, swelling, aching of the muscles and more.

Communicating with the Body

The immune system communicates with the body, when a pathogen is detected in the body, the immune system sends out signals, warning the body that it is being attacked.

The immune system then tells the attacking cells where the problem is, and the cells go to the area to destroy the pathogens.


The tiny microbes that cause diseases are also called antigens. Antigens can cause the immune system to react in different ways and one way is the produce a protein that is used to fight the antigens.

These proteins are called antibodies.


The antibodies are good cells and it is important for the immune system to know the difference between good cells and bad cells.

The antibodies are designed to only connect with certain antigens, and these are the bad cells. The antibodies know not to fight the good cells, only the bad ones.

White Blood Cells

The immune system has cells that do different functions and the cells are found within the blood stream. These cells are called white blood cells.

The white blood cells help to fight infection in the body. These cells have different names and do different jobs.

Jobs of Different Cells

The B cells are called B lymphocytes and they help to make antibodies that fight the antigens. Each of the B cells fight one specific sickness, such as the flu.

The T cells are called T lymphocytes. These cells help to get rid of cells that are already infected in the body.

Helper T cells tell the B cells when to make antibodies and tell the killer T cells when to attack.

Killer T cells destroy cells that are infected.

Memory cells remember which antigens have already caused the body trouble and they are prepared if the antigens come back.

Natural and Acquired Immunity

The body’s immune system is very smart, and it can fight infections that are new in the body.

There are two ways that our body can be immune and that is natural immunity which means that we are born with different immunities.

The other way is acquired, and this happens when we get sick and our body learns how to fight off the diseases.


People can also become immune through vaccines. Vaccines work because the vaccine puts the microbes that have already been killed into the body.

The microbes are already dead, so the body does not get sick, but this teaches the immune system what to look for if this antigen goes into the body.

Facts About the Immune System

  • Babies get antibodies from their mother’s milk.
  • When babies grow in the womb, they form antibodies.
  • Our bodies produce antibodies to fight infections.
  • Some immunities go away, and people need new vaccines if this happens.
  • Different people have a different strength of immune system and can fight off different diseases.
  • Sometimes immune cells get confused and attack good cells.
  • The body responds faster the second time that it sees the antigen.
  • Diabetes is caused when T cells attack the pancreas.
  • Having a high temperature can help build the immune system to fight off infection.
  • When there is fluid where an infection is, this is a sign that the white blood cells are fighting for the body.

What Did You Learn?

  • What does the immune system do? The immune system helps the body to fight pathogens and antigens that cause diseases.
  • How does the body know when a pathogen or antigen is in the body? The immune system sends out signals and tells the good cells to attack.
  • What is important for the antibodies to know? It is important for the antibodies to know the difference between good and bad cells.
  • What do white blood cells do? White blood cells help to fight infection in the body.
  • What sometimes happen to the immune cells? The immune cells sometimes get confused and attack good cells.
  • What are the two types of immunity in the body? The body has both specific immunity and non-specific immunity.
  • What are two ways that people become immune? Two ways people become immune are natural and acquired immunity. Natural immunity means we are born with the immunity and the body automatically fights it off and acquired immunity means that the body has to learn that the cells are bad before it fights them off.