5 facts about lymphocytes


Lymphocytes are a type of white blood cell (WBC). There are two flavors: T cells and B cells. Both play an important role in your immune system, helping your body fight infection and disease.

This article explores five key facts about lymphocytes, including where they are found, what they look like, how they differ, how doctors examine them, and what diseases are associated with them.

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Where they are located

Like all blood cells, lymphocytes begin their journey in the bone marrow , which is a soft, spongy tissue located in the center of the bones.

After the formation of lymphocytes in the bone marrow, they move to the lymphatic system and perform various functions.

Your lymphatic system is an intricate network of lymphatic ducts, nodes, tissues, and organs that work together to release lymphocytes and other infection-fighting cells.

Tiny bean-like structures called lymph nodes are strategically located along the network of lymphatic channels. Lymphocytes can travel to your lymph nodes, where they track down and destroy foreign invaders such as bacteria, viruses, parasites, fungi, and other toxins.

In addition to the lymph nodes, lymphocytes can also accumulate in various lymphoid tissues and organs in the body, such as the spleen , tonsils , intestines, and the lining of the airways.


Lymphocytes are white blood cells found in the bloodstream, lymph nodes, lymphatic ducts, and various tissues and organs such as the spleen and intestines.

Lymphocyte types

There are two main types of lymphocytes: T cells and B cells.

T cells

T cells are involved in cell-mediated immunity, which is essentially cell-to-cell warfare.

T cells travel from the bone marrow to the thymus , a small gland located behind the breastbone, where they begin to mature into a specific type of T cell.

The different types of T cells include:

  • Cytotoxic T cells that find and directly attack "outsiders" such as bacteria, viruses, and cancer cells.
  • Helper T cells that attract other cells of the immune system and organize a specialized immune response.
  • Regulatory T cells are believed to suppress the immune system so that it does not overreact, as in autoimmune diseases.
  • Natural killer T cells (NKT) , which respond to the presence of cancer cells in the body.
  • Memory T cells that remember markers on the surface of alien invaders they have seen before.

B cells

Once formed in the bone marrow, B cells enter the spleen and lymph nodes.

Unlike T cells, B cells do not kill invaders on their own. Rather, they produce Y-shaped proteins called antibodies that stick to the surfaces of invaders and deactivate them or serve as markers for destruction by other cells of the immune system. This process is called humoral immunity.

There are two main types of B cells:

  • Plasma cells produce large volumes of antibodies that stick to foreign invaders in your body.
  • Memory B cells help your body remember foreign invaders if they re-infect your body in the future.


There are two main types of lymphocytes. While B cells help the body identify things that could harm it, T cells primarily seek out and destroy them.

how do they look

Lymphocytes are not visible to the naked eye. This means that they can only be seen when a drop of blood is smeared on a glass slide, treated with the desired stains, and placed under a microscope.

Under the microscope, there will be more and less lymphocytes compared to red blood cells , which carry oxygen and give blood its color.

Furthermore, lymphocytes are made up almost entirely of a nucleus, which is a DNA storage structure located in the middle of the cell. With correct staining, the lymphocyte nucleus turns dark purple and the jelly-like fluid that surrounds it, the so-called cytoplasm, is light pink in color.


Your doctor may order a lymphocyte test if he suspects or is monitoring the progression of certain health conditions.

A simple blood test, called a complete differential blood count (CBC) , can reveal the percentage of lymphocytes and other white blood cells in the bloodstream.

A more advanced test called flow cytometry can identify and count all types of cells in the blood, including lymphocytes.

With the help of flow cytometry, blood is drawn from a vein and sent to a special laboratory, where it is weighed in liquid and passed through a special laser instrument. The light emitted by the laser scatters the cells so that they can be analyzed individually.

The normal lymphocyte count depends on your age. In healthy young and middle-aged people, it typically ranges from 780 to 3,500 lymphocytes per microliter of blood.

Accompanying diseases

Too many lymphocytes in the blood are called lymphocytosis and too few are called lymphopenia .

Any of them can indicate a new diagnosis, indicate a worsening of an existing one or indicate the consequences of certain medical procedures.

Possible causes of lymphocytosis:

Possible causes of lymphopenia include:

Call your doctor

It is important to see your doctor if you experience persistent, recurring, or severe symptoms of an infection or disease throughout your body. Some of these symptoms can include fever, weight loss, unusual tiredness, swollen lymph nodes, and night sweats.


Lymphocytes are white blood cells that work diligently to fight infection and disease in your body. They are produced by the bone marrow and travel through the lymphatic system.

The normal lymphocyte count depends on your age. Too much or too little can be a sign of a mild or serious illness.

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