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Lymphocytes are one of the five white blood cells. Each white blood cell has a specific function but works together to fight illnesses and diseases. Your white blood cells are important to your immune system’s function.

These cells help the body fights antigens, such as viruses, bacteria and other toxins that cause sickness. A weakened immune system means you do not have enough white blood cells in your bloodstream.

How do lymphocytes work?

Lymphocyte production in the body takes place in your bone marrow. Most lymphocytes move through the lymphatic system, and some enter your bloodstream. The lymphatic system consists of a group of organs and tissues, such as lymph nodes, tonsils and the spleen, which protect the body from infection.

Around 25% of the produced lymphocytes remain in the bone marrow to form B cells, while the remaining 75% enter the thymus to become T cells.

Different kinds of T and B cells are available. They include:

The B and T lymphocytes work together to fight infection

What are the roles of B and T cells?

The B cells recognise antigens and form plasma cells that produce antibodies to fight off the infection.

Three T cell types are available, each with a specific function. They include:

B and T cell screening

If you experience an infection or blood disorder symptoms, your overall lymphocyte count will be abnormal. In this case, the doctor may order a B and T screen. This blood test checks the number of lymphocytes in your bloodstream. An elevated or low lymphocyte count may indicate an illness.

You will have your blood drawn at the lab or doctor’s office for this test, and the blood analysis will be in the lab. Your healthcare provider will receive the test result and explain its implications.

A few factors can affect your blood test result, so ensure you inform your doctor if you:

What do the test results mean?

Different laboratories have varying ways of measuring their blood test results. These results vary depending on the following:

The table below gives the approximate ranges for adults.

Test Normal cell count Normal range (differential) Low levels High levels
Lymphocytes 800 – 5000 (0.8 – 5.0) lymphocytes per mcL 18 – 45% of total white blood cells Fewer than 800 lymphocytes per mcL Greater than 5000 lymphocytes per mcL
White blood cells (WBC) 4500 – 10000 (4.5 – 10.0) white blood cells per mcL 1% of total blood volume Critical when ˂ 2500  lymphocytes per mcL Critical when ˃30000 lymphocytes per mcL

Causes of low lymphocyte counts 

Lymphocytopenia or low lymphocyte count often occurs for the following reasons.

A low lymphocyte count may occur from several diseases and conditions. They include mild infections or the flu, which aren’t serious for most people, but lymphocytopenia increases your risk of infection.

Other conditions that may cause a low lymphocyte count include:

Causes of high lymphocyte counts

An elevated lymphocyte count or lymphocytosis is common during an infection. High lymphocyte levels that remain for a prolonged period may indicate a more serious disease or illness, such as:

Questions to ask your doctor

Asking your doctor the following questions if they order, a B and T cell screening is necessary.

You can visit our Clinic at Suite E, 117a Harley St, Marylebone, London W1G 6AT if you need B and T cell screening tests. Our healthcare professionals can perform a lymphocyte blood test. Call us today on 02071830244 for more information on our tests or to schedule an appointment for your B and T cell test.