Parts of the Immune System

Bacteria and viruses can enter your body through openings in your body, such as your nose, mouth, anus and vagina, as well as through accidental scrapes or cuts. Because of this, your immune system’s organs are spread throughout your body for quick, lethal results.

Organs of the Immune System

Bone Marrow

The bone marrow is located at the center of all bones. Your immune system’s white blood cells are your main bodyguards, and all of them are produced in your bone marrow, along with your red blood cells and platelets.


The thymus is a gland located between your heart and sternum. Certain types of white blood cells are made in your bone marrow and then travel to your thymus, where they develop into mature white blood cells.


Your spleen is essentially a “chat room” where many white blood cells mingle and share antigen blueprints. These blueprints are used by the white blood cells to produce antibodies that will bind and destroy a specific antigen. Many antibodies are produced in the spleen, which also removes old, tired and non-functioning red blood cells.

Lymph Nodes

Your lymph nodes are round organs found throughout your body, except in your feet, that serve to filter out and kill antigens. They are connected by a network of tubes, called lymphatic vessels, which carry lymph, a fluid that fills the spaces between the cells in your body. Lymph picks up bacteria and carries it back to your lymph nodes where high concentrations of white blood cells are waiting in ambush. The lymph nodes swell when an infectious agent enters your body and white blood cells make many more copies of themselves, such as when you have a sore throat.

Cells of the Immune System

White Blood Cells

The main cells that make up your immune system are white blood cells. There are many types of white blood cells, each with a specific job which helps the body destroy a wide variety of antigens. These cells are responsible for ingesting and destroying antigens, and act as switches to turn your immune response “on” and “off.”  Phagocytes, T cells, B cells, and memory cells are all types of white blood cells.


Many different types of white blood cells are phagocytes. All phagocytes “eat” antigens. Macrophages are one type of phagocyte found throughout your body.

T Cells

There are several types of T cells including helper T cells, killer T cells, and suppressor T cells.  Helper T cells release chemicals that let other white blood cells know that an invader is present, and prepares those cells to attack.  Killer T cells identify and destroy infected cells.  Suppressor T cells are responsible for turning off your immune response.

B Cells

B cells produce antibodies called glycoproteins, which are proteins with sugars attached. Each antibody has the blueprint for a specific antigen.

Memory Cells

Once B Cells and T Cells have successfully eradicated an antigen, a few of them will remain in your body as customized memory cells. If the same antigen re-enters your body, these memory cells would mobilize to destroy the antigen before you felt sick.