Organs of the Human Immune System

Organs of the Human Immune System

The human immune system is comprised of organs and cells that work together as an eminent network that defends the body against bacteria, fungi, parasites, and viruses. The organs involved are called the lymphoid organs. Each of them plays a role in the growth, development, and the release of lymphocytes (a certain type of white blood cell). The lymphoid organs depend on the blood vessels and lymphatic vessels to transport the lymphocytes to and from various parts in the body. [1]

Bone Marrow

The spongy, tissues that are inside the bones located on the ribs, hip, thigh and breasts are known as the bone marrow. They also exist in the spine and skull. The stem cells, which are immature, develop into white blood cells that fight infections, red blood cells that carry oxygen throughout the body and the platelets that makes it possible for blood to clot. [2 – 3]

All the cells of the immune system originate from the bone marrow before they migrate to other parts of the body. Hematopoiesis results in stem cells that are developed in the bone marrow moving on to two different routes. They may stay in the bone marrow and mature there, or they may be precursors of cells that direct themselves out of the bone marrow to finalize their maturation on another spot. Lastly, the pertinent bone marrow also produces a list of other precious cells: immature thymocytes, natural killer cells, platelets, red blood cells, granulocytes, and B cells. [1]

Lymph Nodes

You can find lymph nodes in many different locations in the body as they behave like an immunologic filter for the bodily fluid in the tissues known as lymph. There are more than 300 of these tiny, bean-shaped glands. [1, 4]

The B cells, dendritic cells, T cells and the macrophages are components of the lymph nodes. The lymph in the nodes has its antigens filtered out before they eventually come back to the lymph, which will then be circulated. An immune system becomes responsive when the dendritic cells and the macrophages that captured antigens show these foreign materials to both T and B cells. [1]


The shape of a spleen is a loose fist, and it is located under on the left side of the diaphragm. It is so small that an adult spleen on average weights less than half of a pound (0.44 lb). [5]

The spleen is made up of red blood cells, natural killer cells, macrophages, dendritic cells, B cells, and T cells, and is an immunologic filter of the blood. The bounty hunters are the roving dendritic and macrophages cells. Those cells haul in captured antigens to the spleen via the bloodstream. As the antigens are shown to the appropriate T or B cells so they will be eliminated. This is how the human immune system becomes responsive to invasions. The spleen can be seen as an army base where the B cells are on duty and produce plethora of antibody. Meanwhile, old red blood cells are trashed, or eliminated, and recycled in the base. [3, 5]

The spleen is also an organ where blood is stored for future use. When there is an opening on the skin, blood will flow around the body coming from the spleen. [5]


The thymus is located in the center of the upper chest, tucked under the breastbone (behind the sternum). Thus, it is tiny. The organ itself resembles the bud of the herb thyme. The thymus is also known as the thymus gland.
[6 – 7] The thymus commences to help produce white blood cells before birth. [6]

The thymus is where mature T cells are produced and then let go to flow along the bloodstream. That is reason they are called T cells. The T cells that may stimulate a harmful autoimmune response are removed. Obviously, the T cells that are useful are kept. Thymus education is the name of the fascinating maturation process. The students are the immature thymocytes (prothymocytes), who go to the thymus for schooling when they leave the bone marrow. [3]

human immune system

White Blood Cells Tem X5000 at Negative


There are still more organs to list, but the source that I used didn’t describe them. A website called Generic Look has explained that they can be divided into primary, secondary, and tertiary lymphoid organs.

The same webpage also has a YouTube video embedded titled: How the Body Works: The Spleen.

There is a webpage at

for kids to read and learn about the organs of the human immune system.

Internal Organs of the Body, Anatomy of the Visceras Dissected, Painted and Engraved Gautier, 1745

by Jacques Fabien Gautier d’Agoty