The 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.

Lymph Node – lymphatic system is a crucial part of your body’s ability to fight off infection.
Bone Marrow – Bone marrow makes blood cells that help to fight infection.
Immunoglobulin (IgE) – This is an antibody that helps fight infection.
Appendix – Protects us From Germs and protects good bacteria.
Macrophage – Help to overcome infection by secreting signals that help activate other cell types to fight against infections.
Lymphocyte – A certain type of white blood cell that fights infection.
Spleen – Your spleen is a small organ found in the upper part of your abdomen, near your stomach. It helps filter your blood and stores platelets and white blood cells, which fight infection.
Thymus Gland – Generate mature white blood cells that help the immune system fight off illness.

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.

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.

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.

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 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.