What Is the Thymus Gland and Why Is It Important? (2024)

The thymus gland, located behind the breastbone and between the lungs, plays a vital role in the immune system. This small organ makes white blood cells, called T-cells, and is important in fighting off infection. It also plays a messaging role in the endocrine system.

Your thymus is most active in your younger years. Certain conditions, as well as advancing age, can lead to thymus-related health issues.

Function

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.

Up through puberty, your thymus gland is very active. Then it starts to shrink slowly. Some researchers believe the shrinking of the thymus may be what triggers the aging process. That's why aging often means getting sick more and responding to vaccines less.

The thymus serves both the immune and endocrine systems, with a role in the following:

• T-cell production: The thymus produces and trains T-cells that help to fight bacteria, viruses, and toxins. They assist with producing antibodies. They also identify and attack cancer cells, and help to prevent autoimmune disorders. The three main types of T-cells include regulatory, helper, and cytotoxic T-cells.
• Hormone production: The thymus gland produces several hormones that regulate immune response. They include thymosin, thymic humoral factor, thymopoietin,and thymulin.

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.

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.
  

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 causes a T-cell deficiency due to an absent or underdeveloped thymus gland at birth, in turn leading to infection risk and immune system problems. This can cause severe combined immunodeficiency (SCID), which is fatal early in life without treatment.
• 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 benign, but thymus cancers can become aggressive and spread to other areas. Thymic lymphomas, germ cell tumors, and carcinoids also occur.
  

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. About 75% of people diagnosed with myasthenia gravis have impaired thymus function.
• 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.
• 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. It 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.