White blood cells are an important part of the body’s immune system. Like all blood cells, white blood cells are made in the bone marrow and have a protective role against invading pathogens and infections. If an infection develops, then white blood cells will gather at the site, attacking and destroying the pathogen causing the infection.
The white blood cell count is the complete number of white blood cells in a blood sample.
The main types of white blood cells are:
White blood cells may also be referred to as leucocytes. Unlike red blood cells, all white blood cells have a nucleus which is what distinguishes them between red cells and platelets.
The number of white blood cells in circulation can give an indication of disease. The different types of white blood cells have slightly different functions.
These are the most common white blood cells in circulation. They protect the body against invasion from bacteria and fungi.
Lymphocytes are found much more commonly in the lymphatic system rather than the blood. There are 2 types of lymphocyte: B and T cells. B cells release antibodies and activate T cells. T cells release cytokines and kill invading pathogens.
These are the biggest white blood cells and migrate to invading pathogens and digest bacteria removing it from the body.
Eosinophils kill larger parasites like worms. They are also involved in the body’s allergic reaction response.
These cells are responsible for allergic and antigen responses by releasing histamine to dilate blood vessels. This increases the flow of blood to the affected tissue and allows easy access for neutrophils and clotting factors.
An increase in the white blood cell count can indicate illness or infection. They may also be increased when the body becomes injured either by a physical or emotional stress or because of excessive exercise. Leucocytosis or an increased white cell count is usually caused by external stimuli such as:
A low white blood cell count is called leukopenia and can be caused by:
You may not be able to directly influence your white blood cell count but with a good lifestyle, you can improve the efficiency of your immune system.
Smoking can also damage your immune system and its response. However, some of the damage is reversible if you stop smoking.
Nutrition is an important factor in our health and immune status. If we are deficient in some nutrients, then this can make our immune system weak. Micronutrients including zinc, selenium, iron, copper, vitamins A, C and E, B6 and folic acid all have important influences on our immune responses. Therefore, it is essential to maintain a healthy and balanced diet incorporating all these micronutrients.
Exercise is key to a healthy lifestyle. However, intense exercise can also induce immunodepression during recovery. Therefore, it is essential that you take rest periods between bouts of intense exercise to prevent illness.
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 Lab Tests Online UK. (2018). White Blood Cell Count. Available at: https://labtestsonline.org.uk/tests/white-blood-cell-count
 Asadollahi, K., Hastings, I, M., Beeching, N, J., Gill, G, V and Asadollahi, P. (2011). Leukocytosis as an Alarming Sign for Mortality in Patients Hospitalized in General Wards. Iran J Med Sci: 36(1), pp 45-49.
 Brodin, P and Davis, M, M. (2017). Human Immune System Variation. Nature Reviews: Immunology: 17(1), pp 21-29.
 Kafeshani, M. (2015). Diet and Immune System. Immunopathologia Persa: 1(1).
 Chandra, R, K. (1997). Nutrition and the Immune System: An Introduction. American Journal of Clinical Nutrition: 66, pp 460S-463S.
 Peake, J, M., Neubauer, O., Walsh, N, P and Simpson, R, J. (2016). Recovery of the Immune System After Exercise. Journal of Applied Physiology: 122, pp 1077-187