What Is a Lymphocyte?

Your lymphocytes are pretty important - here's how they protect you

B-cell lymphocyte
A B cell lymphocyte under the microscope. Stocktrek Images/Getty Images

A lymphocyte is a small white blood cell that plays an outsized role in defending your body from disease.

Lymphocytes fight infections by producing antibodies, which are chemicals that help stop and then remove foreign invaders such as bacteria, viruses, fungi, parasites and toxic chemicals. Lymphocytes also kill cells in your body that are infected with a pathogen, and release chemicals to warn other cells of the danger.

Although there's some evidence that one type of lymphocytes may attack and destroy the infectious agent directly, for the most part lymphocytes leave that task to other types of white blood cells, including phagocytes.

Lymphocytes move around your body through the lymphatic system, which is part of the circulatory system. Lymph vessels carry clear fluid, including lymphocytes and other white blood cells, throughout your body to fight infection.

There are two main types of lymphocytes: T cells and B cells. Each has a specific role to play in your health. Read on to learn more about them.

What Are T Cell Lymphocytes?

T cell lymphocytes' job is to scan cells for infection. When a lymphocyte spots a cell that's been infected with bacteria or a virus, the lymphocyte will proceed to kill the cell (and will remember the infectious agent, so it can act faster the next time it encounters the same problem).

These lymphocytes also kill cancer cells, which is why one promising approach to cancer treatment involves isolating, multiplying and then using a patient's own T cells to fight a particular cancer. In addition, there's some evidence that T cell lymphocytes also can protect you from bacteria by actually capturing and killing the bacteria in question.


The "T" in T cell stands for thymus, the small gland in your chest where T cells go to mature after they're manufactured by your bone marrow.

What Are B-Cell Lymphocytes?

B cell lymphocytes don't attack and kill cells, viruses or bacteria themselves. Instead, they manufacture proteins called antibodies that actually stick to the surface of invaders, disabling those invaders and spotlighting them for clean up by other parts of your immune system.

Although each B cell only produces one specific antibody, your body's huge number of B-cells collectively recognize an almost unlimited number of intruders and produce a tremendous variety of antibodies to fight them.

Like T cell lymphocytes, B cell lymphocytes also are made in your bone marrow. They mature in your spleen.

What Can Go Wrong with Lymphocytes?

Lymphocytes don't always behave in your best interests.

In autoimmune disease, for example, T cell lymphocytes mistakenly attack your own tissues, mistaking your cells for foreign invaders. Celiac disease, for example, involves an autoimmune attack on the lining of your small intestine.

Scientists aren't certain what propels T cells to do this.

You also can develop cancer that specifically affects your lymphocytes. This type of cancer is called Hodgkin's disease or non-Hodgkin lymphoma, and there are several different types, all determined by the lymphocytes involved. Hodgkin's disease involves only the B cell lymphocytes, while non-Hodgkin lymphoma can involve either the B cell or T cell lymphocytes.


Cruz-Adalia A et al. T cells kill bacteria captured by transinfection from dendritic cells and confer protection in mice. Cell Host & Microbe. 2014 May 14;15(5):611-22.

Sharpe M et al. Genetically modified T cells in cancer therapy: opportunities and challenges. Disease Models & Mechanisms. 2015 Apr;8(4):337-50.

U.S. Library of Medicine. Lymphocytes fact sheet. Accessed Jan. 16, 2016.

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