Lymphocyte count
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Lymphocyte countFull blood count

Lymphocyte count

May 3, 2022

Lymphocyte count

What is a lymphocyte count?

Lymphocytes are a type of white blood cell that develop in the bone marrow, before maturing and exiting into the bloodstream. Mature lymphocytes are found in the blood and lymph tissue.

After developing in the bone marrow, some lymphocyte cells travel to the thymus, where they become T cells. Other lymphocytes stay in the bone marrow, where they become B cells. Some of them also develop into NK cells.

Why is this analysis important?

Like other types of white blood cells, lymphocytes play a key role in helping the body’s immune system fight cancers or foreign viruses, bacteria and parasites.

What are some of the causes of a high lymphocyte count?

A high lymphocyte count, also called lymphocytosis, is usually due to an infection. This is the opposite of lymphocytopenia, which is a low lymphocytes count. A low lymphocyte count can indicate certain viral diseases, including COVID-19.

To get a full picture of white blood cell health, you can have a lymphocytes blood test as part of a complete blood count.

During an infection or illness, the body often produces extra lymphocytes to help fight it. After infection, there will be leftover lymphocytes due to the body’s overproduction, however, these are usually harmless and asymptomatic.

Alternatively, a high lymphocyte count can represent something more serious. It can indicate a problem with the bone marrow or the way the body produces white blood cells. This can be a sign of a condition such as cancer of the blood or lymphatic system. It could also indicate an autoimmune disease.

What are some of the causes of a low lymphocyte count?

Lymphocytopenia, also referred to as lymphopenia, occurs when the lymphocyte count in your bloodstream is lower than normal.

Lymphocytopenia may be a sign of an underlying illness, condition, or other factors. The majority of causes are acquired. This means that you develop rather than inherit them.

T cells make up the greatest proportion of lymphocytes, and T-cell lymphocytopenia is the most common. However, this condition can affect all three cell types.

Some of the causes of lymphopenia include among others:

  • Autoimmune disorders

  • Cancer and treatments for cancer

  • Diseases that affect the blood and bone marrow

  • Infections

  • Malnutrition

  • Genetic features

  • Gastrointestinal conditions such as amyloidosis and celiac disease

  • Some medications

Other considerations

There are three main types of lymphocytes that work together to help identify and eliminate infections and other diseases:

  • B cells make antibodies and signalling proteins that help to flag or attack invading bacteria, viruses, and toxins.

  • T cells seek and destroy the cells that have become infected or are cancerous, and they also communicate with B cells.

  • Natural killer (NK) cells contain compounds that can kill cancer tumour cells and cells infected with a virus.

Low levels of T cells or too few NK cells can lead to uncontrolled viral, fungal, and parasitic infections. B-cell lymphocytopenia can lead to an increase in harmful and different types of infections.