July 21, 2020

What are Lymphocytes?

Lymphocytes are a major type of white blood cell, accounting for approximately a quarter of the total white blood cell count. However, the concentration of lymphocytes in the blood increases when an infection is present.[1] Lymphocytes consist of cells which have vital roles in the body’s immune system, such as natural killer cells, T cells and B cells.

Why take a Lymphocyte blood test?

Lymphocyte levels vary between individuals and depend upon age, gender, location, lifestyle choices and general health. If levels are abnormally high or low, then this could indicate infection or disease. Therefore, if you are experiencing symptoms of infection, a lymphocyte count may help to confirm this.

You can check your level of lymphocytes together with other white blood cells within Forth’s Vitality and Ultimate blood tests.

What function does Lymphocytes have in the body?

The two major forms of lymphocytes are B and T cells. These are the most important cells in the adaptive immune response. The adaptive immune response’s main function is to destroy invading pathogens and any toxic substances they produce. However, it is important that the adaptive immune system only responds to a foreign invading pathogen because its response is extremely destructive. It’s the ability to distinguish between something which is foreign and from the host itself, which makes the adaptive immune system so important.[2]

The adaptive immune response is executed by lymphocytes. There are two classes of lymphocytes which carry out different responses.

B Cells

B cells are produced in the bone marrow and are associated with antibody responses. B cells release antibodies when they are activated, called immunoglobulins. These antibodies travel in the bloodstream and can pass through other bodily fluids until they reach the pathogen which stimulated their production. The antibodies bind to the invading antigen, inactivating a virus or microbial toxins and preventing them from binding to the host cells. Antibody binding is a process which marks invading pathogens for destruction, making it easier for the innate immune system to recognise the invader and destroy it.[2]

T Cells

T cells, on the other hand, are associated with cell-mediated immune responses. There are different types of T cells which react differently to invading pathogens. For example, some T cells might kill a host cell which has become infected and has viral antigens on its surface, killing the cell before the virus has managed to replicate and cause further damage. Other T cells can produce signal molecules which activate other immune cells to destroy pathogens which are identical to the ones being destroyed by the T cells.[2]

How do changes in Lymphocytes affect health and wellbeing?

Lymphocytes are a marker for infection which can affect the way you feel and may interrupt with your everyday life. Usually, an increase in lymphocytes reflects a viral infection. A low lymphocyte count can also signify an infection such as human immunodeficiency virus (HIV). A low lymphocyte count is associated with an increased risk of infection post-surgery or trauma.

An infection often reduces energy levels and can reduce your mood, making you feel generally unwell. Plus, infections are more likely to occur during the colder, winter months which may also reduce your mood.

If you are worried about your immune levels or just want to check where you fall on the range, you can test your lymphocytes level with Forth’s leading blood test service.

​What can cause Lymphocytes to change?

Lymphocytes can increase when an invading pathogen enters the body causing an infection. Viral infections are a common reason lymphocyte levels increase.

A decrease in lymphocytes has been linked to immunodeficiencies such as HIV or AIDS. Therefore, a reduction in lymphocytes could mean there is a problem with the immune system.


What are the most common symptoms?

The symptoms of a viral infection depend on the infection itself. For example, the common cold is a type of viral infection. The common symptoms of a cold are:

  • Blocked nose or runny nose
  • Sore throat
  • Headaches
  • Coughs
  • Muscle aches
  • High temperature
  • Sneezing
  • Pressure in the ears and face
  • Loss of taste and smell[3]

How to keep Lymphocytes in the healthy range

There are many factors which can impact on immune dysfunction, such as:

  • stress
  • malnutrition
  • exposure to contaminants

Diet is a key factor in the function of the immune system. It is important to get the right calorie and protein intake because not getting enough, can reduce the T cell memory function in response to antigens. Vitamins are also vital, particularly vitamins A, C and E. Vitamin A has roles in the control of both the innate and adaptive immune responses as well as helping to mature T cells in the thymus. While vitamins C and E help lymphocytes to proliferate.[4]

Staying hydrated is also vital for the immune system status. Saliva contains the antibody, IgA, which acts as the body’s first line of defence against infection. For that reason, the body needs enough fluid to ensure enough saliva is produced. Equally, the liquid part of the blood consists of water and so, hydration is important to keep the blood volume at adequate levels, especially as many immune cells travel in the bloodstream to reach their target.


[1] Lab Tests Online UK. (2017). Lymphocyte. Available at:

[2] Alberts B, Johnson A, Lewis J, et al. Molecular Biology of the Cell. 4th edition. New York: Garland Science; 2002. Chapter 24, The Adaptive Immune System. Available from:

[3] NHS. (2017). Common Cold. Available at:

[4] Kafeshani, M. (2015). Diet and Immune System. Immunopathologia Persa: 1(1).

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This information has been medically reviewed by Dr Nicky Keay

Nicola has extensive clinical and research experience in the fields of endocrinology and sport and exercise medicine. Nicky is a member of the Royal College of Physicians, Honorary Fellow in the Department of Sport and Exercise Sciences at Durham University and former Research Fellow at St. Thomas' Hospital.

Dr Nicky Keay

Dr Nicky Keay

BA, MA (Cantab), MB, BChir, MRCP.