Leukocytes (white blood cells): low, high, cause, normal

Leukocytesalso called white blood cellsare immune system cells that form in the bone marrow and which are present in the blood, in the lymph, the lymphoid organs and certain tissues. Since leukocytes increase in case of infectioninflammation or dysfunction of the bone marrow, measuring their rate is very useful. The assay is also used to monitor the body’s reaction to different treatments. How to interpret his blood test?

THE white blood cells, also called leukocytes, are cells produced by the bone marrow. They constitute the immune system and intervene in particular in the fight against infections by protecting the body against external aggressions such as bacteria or viruses. White blood cells are present in the blood, lymph nodes, spleen, tonsils, adenoids and lymph. It exists three main categories of leukocytes: monocytes, lymphocytes and polymorphonuclear.

THE monocytes (macrophages) represent 7% leukocytes. In adults, there are 2 to 8 monocytes per 100 white blood cells. Like many blood cells, monocytes are made by an organic tissue contained in certain bones, the bone marrow. They are the main players in phagocytosis after their transformation into phagocytes, a mechanism by which the cell absorbs unwanted microorganisms to destroy them.

THE lymphocytes represent 30% of leukocytes. We distinguish B cells (the B lymphocytes produce antibodies specific to an antigen: the antibodies attach themselves to the antigens, such as a bacterium, in order to destroy it) and T cells (secreted by the thymus before becoming thymocytes, these cells divide and multiply rapidly when exposed to an antigen). They are part of acquired immunity: that is, it is not present at birth or immediate, unlike the innate immune response, and only intervenes when a person’s immune system encounters and recognizes foreign infectious agents called “antigens” (bacteria, virus, fungus, parasite…).

THE polynuclear carry out what is called “phagocytosis”, that is to say that they attack foreign bodies in the event of infection. They are part of the innate immune system, present from birth. This is the body’s first response when attacked by a pathogen. There are three kinds of polynuclear: neutrophils (60% leukocytes), eosinophils (2 to 4% of white blood cells) and the basophils (1% of leukocytes).

THE neutrophils represent 60 to 70% of white blood cells. They help fight bacteria. Polymorphonuclear are the first cells to intervene during a bacterial infection. A decrease in the neutrophil count corresponds to neutropenia and an increase in the neutrophil count corresponds to neutrophilia.

THE polymorphonuclear eosinophils intervene in the allergic reactions and the fight against the parasitic infection. Eosinophils represent 2 to 4% of white blood cells. Their increase, called eosinophilia, with rates above 4%, testifies to an allergic ground or a parasitosis.

THE polynuclear basophils intervene during allergic reactions: they are responsible for the release of mediators, such as histamine, at the origin of the inflammatory reaction of the allergy. Their number is around 0.5 to 1% of white blood cells. An increase in their rate, greater than 1%, corresponds to basophilia which is observed during certain leukaemias, hepatic or thyroid pathologies.

The concentration of leukocytes in the blood is characterized by a count of the blood formula (NFS or hemogram): this count makes it possible to count all the elements of the blood. The number of white blood cells is normally between 4,000 and 10,000/mm³ of blood in men or women, but these standards may vary slightly depending on the technique used in the laboratory. Below 3,500 leukocytes per mm³we speak of leukopenia, above 10,000 leukocytes per mm³It’s about a hyperleukocytosis. Between 10,000 and 15,000, we say that it is moderate, beyond 15,000, we speak of frank hyperleukocytosis. Note that during the last weeks of pregnancy, the leukocyte rate may be higher: it is the concentration of neutrophils which increase in pregnant women.

The leukocyte test is prescribed by a doctor, if he thinks you might have an infection, an inflammatory disease, an immune deficiency, a bone marrow disease or an allergy but also to make sure that a treatment which you is administered does not cause abnormalities in white blood cells. Generally, the examination consists of taking a blood sample from a vein in the arm or by pricking the fingertip. You do not need to be fasting to perform this test.

Cancers do not give rise to an increase in white blood cells, except leukaemias.

A decrease in lymphocytes makes it possible to understand that there is leukopenia and therefore a body’s immune deficiency : that is to say that one of the components of the immune system is defective or absent. THE patient is therefore more susceptible to infections. It may be a defect in the cells of the immune system or an external factor (environmental factor or external agent) which has affected the immune system (burn, malnutrition, medication, vitamin B9 or B12 deficiency…), a liver pathology, a polyarthritis rheumatoid or one lupus… It is not necessarily necessary to worry immediately: other examinations will be necessary to determine the cause, make a diagnosis (thanks to a simple clinical examination (possible presence of an enlarged spleen, lymph nodes fat, fever…), a blood count, a bone marrow aspiration or a biopsy depending on the case) and consider an appropriate treatment (it may be a stimulation of the production of white blood cells, or stimulation of the bone marrow and often, a supply of vitamin B or even treatments based on cytokine, a protein regulating cellular activity). Finally, antibiotics can be prescribed to fight infectious diseases, to which the patient is more vulnerable in case of leukopenia.

• Lymphocytes. They increase in case of viral infections (cold for example) or bacterial or in case of autoimmune disease.
• Monocytes. They increase in case of chronic infectious diseases or inflammations.
• neutrophils. They increase in the event of bacterial infections (during sinusitis, nasopharyngitis, bronchitis, pyelonephritis, appendicitis, for example) or if the patient takes treatment with corticosteroids.
• Polymorphonuclear eosinophils. It increases in case of allergic reactions or during a parasitic infection.
• Polymorphonuclear basophils. They increase in the event of allergic reactions or during an infection.

What will put the doctor on the trail of such and such a cause is the clinical examination (presence of fever, cough, state of fatigue, pain…). But to establish a diagnosis, the symptoms will also be compared to other medical imaging tests or a myelogram (microscopic analysis of bone marrow cells). Boosted immunity is common, especially in winter and seasonal changes, and an increase in white blood cells is often mild. Always transfer your results to your doctor or to the prescribing doctor who can direct you, if the results are abnormal, towards additional examinations or prescribe an appropriate treatment. Normally, white blood cells are expected to decrease when the infection or inflammation is cured. The doctor may therefore prescribe another blood sample to make sure that everything is fine.