What Is the Thymus Gland?

The thymus gland, located behind the breastbone and between the lungs, plays an important role in developing the immune system. This small organ makes white blood cells, called T-cells, and plays a huge part in training your body to fight infections and cancer cells.

It's also vital to the body's chemical messaging or endocrine system. However, it's only active from when you're born until you become a teenager.

Read on to learn more about the role of the thymus in immunity, autoimmunity, and aging, as well as how several disorders may affect this important organ.

What Does the Thymus Do?

From the time you're conceived until you reach puberty, your thymus gland is very active. It serves both the immune and endocrine systems. That's the system that makes hormones, the body's chemical messengers.

T-Cell Production

The thymus produces and trains T-cells, known as thymus-derived lymphocytes. These cells help fight off the body's foreign invaders, such as bacteria, viruses, and toxins. They can also identify and attack cancer cells.

Once T-cells are produced, they undergo "positive and negative selection" within parts of the thymus known as the cortex and medulla. This process teaches T-cells how to identify foreign substances or toxins and avoid harming healthy cells in the body.

This prevents autoimmune disorders. These are medical conditions where things go wrong, and your cells attack your body tissues and cells instead of foreign invaders.

Hormone Production

The thymus gland produces several hormones, including:

• Thymopoietin and thymulin: These hormones are involved in the process where T cells get turned into different types of disease fighters.
• Thymosin: This hormone boosts the immune system's response. Thymosin also stimulates hormones that control growth.
• Thymic humoral factor: These hormones increase the immune system's response to viruses.

The thymus gland also makes small amounts of hormones produced in other areas of the body. These include melatonin, which helps you sleep, and insulin, which helps control your blood sugar.

Where Is the Thymus Located?

The thymus gland is usually located behind the breastbone, in front of the heart and between the lungs. In some people, though, this organ is found in the neck or upper chest.

The thymus gland.

Types of Thymus Cells

Inside the thymus gland, there are many different cells:

• Epithelial cells line all body surfaces and act as a protective barrier.
• Kulchitsky cells make hormones, chemical messengers for the thymus and other cells.
• Thymocytes are cells that become mature T lymphocytes, specialized infection fighters.
• Dendritic cells are found in the skin and other tissues. They help protect against toxins and other foreign substances.
• Macrophages are cells that are sometimes called the "garbage trucks" of the immune system. They eat foreign matter and clear away tumors.
• B lymphocytes are cells that make antibodies, proteins that attack viruses and bacteria.
• Myoid cells are muscle-like cells. Scientists believe they trigger the autoimmune response in a muscle disorder.

This list hints at how complex the thymus gland's job is. Its role also changes throughout your life.

Associated Disorders

Many conditions can affect the thymus gland, ranging from genetic disorders to cancers in older adults. These can lead to problems with immunity and autoimmunity.

These conditions include:

• DiGeorge syndrome: This is a rare developmental disorder in which the thymus gland is underdeveloped or absent at birth. This leads to a dangerous deficiency in T-cells, causing serious immune system problems and a high risk of infections.
• Thymic hyperplasia: With this condition, the thymus becomes swollen and inflamed. This can occur in autoimmune disorders such as myasthenia gravis (MG), lupus, and rheumatoid arthritis (RA).
• Thymic cysts: Cysts are abnormal growths filled with liquid. They're tiny, less than 3 centimeters (cm). Thymic cysts are usually not a problem.
• Tumors of the thymus gland: Thymomas are tumors that occur within the thymus gland. They can be harmless or cancerous. They can also occur in the neck, thyroid gland, or lungs. Other tumors that may occur in the thymus include thymic lymphomas, germ cell tumors, and carcinoids.
  

Sometimes persons with thymomas can develop other immune conditions. These include:

• Myasthenia gravis (MG): This is a condition where your muscles weaken and tire, and you lose your ability to control them. This autoimmune condition occurs in up to 25% of people with thymomas.
• Pure red cell aplasia: This is a condition where your T-cells attack young red blood cells. This causes severe anemia, a lack of oxygen-carrying red blood cells. It occurs in roughly 5% of people with thymomas.
• Hypogammaglobulinemia: This is a condition where the B-cells don't make enough antibodies. It occurs in roughly 10% of people with thymomas.
• Thymoma-associated multiorgan autoimmunity: This condition is similar to the rejection seen in some people with organ transplants. In these cases, the tumor produces T-cells that attack a person's body.

Summary

The thymus gland plays a vital role in training the immune system to protect the body against infections, even cancer. If fosters the growth and development of T-cells, a type of white blood cell that can help fight against infection and foreign invaders.

Conditions that affect the thymus gland can lead to problems with immunity and autoimmunity. If you think you're experiencing symptoms related to your thymus, reach out to your healthcare provider right away.