The immune system is the body’s natural defense system to help fight infections and other diseases.¹ Its job is to prevent or limit infections by recognizing and destroying foreign substances known as pathogens such as bacteria and viruses and abnormal or unhealthy cells such as cancer cells.² When the immune system is defending the body against infection and disease, it is called the immune response.²

The immune system is made up of a complex network of different organs, special cells, and substances that work together to protect the body and respond to infection and disease.² We can describe the immune system as an army. It has many different kinds of “soldiers”, all with different functions that work together to protect the body. Some of these soldiers recognize the unhealthy cells, others communicate with other cells or tissues in the body, while others are the fighters that attack and destroy the enemy.

The components of the immune system consist of
cells, tissues and organs including:

Blood Cells

White blood cells called lymphocytes are part of the immune system. They are produced in the bone marrow. Main types of lymphocytes are: ²

B-cells
(also called B lymphocytes)

They fight bacteria and viruses by making proteins called antibodies. The antibody locks onto the surface of the invading bacteria or virus. B-cells can also remember the types of infection and disease the body has fought against in the past. If the same germ gets into the body, B-cells can quickly make more antibodies to help fight it, so the body does not get sick.

T-cells
(also called T lymphocytes)

They help control the immune system, assist B-cells to make antibodies, and may attack abnormal cells.

Natural killer cells
(also called NK-cells)

They attack cancer cells or cells that are infected with a virus.

The lymphatic system

This is the group of tissues and organs that make and store cells that fight infection and disease. The lymphatic system includes the tonsils, spleen, thymus, lymph nodes, lymph vessels and bone marrow.²

Skin and mucous membranes

They are the body’s first line of defense against infection and disease. The skin prevents most germs from getting into the body. Mucous membranes that line many parts of openings in the body such as the mouth, nose, throat, anus or vagina help to protect the body. Cells of the mucous membrane also make fluids and substances that help destroy germs.²

The immune system is essential for our survival. Without an immune system, our body would be exposed to a world full of dangerous microbes. It is our immune system that keeps us healthy as we drift through a sea of pathogens.