What Is the Role of the Thymus Gland?

Updated July 19, 2017

The thymus is a ductless gland beneath the breastbone. It plays an essential role in the body's immune system function. The immune system is the body's defence system against viruses, disease and invaders of all kinds. Healthy thymus function is critical to a strong immune system, which results in better overall general health.


The thymus plays an essential role in the body's response to disease invasion. About half of the white blood cells created in the bone marrow go directly into the bloodstream and tissue fluids; the remaining portion must pass through the thymus gland where they are processed into thymic lymphocytes, or T-lymphocytes.


T-lymphocytes play an important role in the body's defence system by stimulating the production and growth of antibodies created by other lymphocytes, stimulating the growth and action of the phagocytes, which surround and engulf invading viruses and microbes and detect and destroy foreign and abnormal tissue in the body.


If the thymus is removed or becomes non-functional during fetal life, the body's cell-mediated arm of immunity fails to develop because the T-lymphocytes have not developed. It is this cell-mediated arm of immunity orchestrated by the thymus gland that is mainly responsible for the rejection of organ transplants and resistance to intracellular microbial infection. The thymus gland is also believed to play a role in the body's natural resistance to cancer.

What Affects the Thymus

The thymus gland continues to grow until a person reaches puberty. As the body ages, the thymus gland naturally shrinks and its function is reduced. In addition, some conditions can impair the functioning of the thymus gland and immune system, including alcohol consumption, smoking, recreational drugs, some medications, high cholesterol, excessive sugar consumption, allergies, exposure to chemicals, food additives, physical and emotional stress and illness.

Related Conditions

In a medical condition known as myasthenia gravis, patients may develop tumours of the thymus gland. While scientists are not completely certain of the role the thymus has in the condition, one theory is that the thymus gland may give incorrect instructions to developing immune cells, which causes autoimmunity and the production of acetylcholine receptor antibodies--two predisposing conditions for an attack on neuromuscular transmission. Symptoms include weakness of the eye muscles, difficulty swallowing, slurred speech, drooping eyelids, blurred or double vision, unstable gait, upper body weakness, shortness of breath and impaired speech.

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About the Author

Jennifer Lanier has been a professional health researcher and writer on the web since 2002. She has published work on several health sites and written e-books on alternative cancer cures and natural hormone balance.