Leukocytes, also commonly known as white blood cells, are blood cells of the immune system. Their levels can fluctuate, sometimes revealing an underlying condition. Here’s some explanation.
What are white blood cells used for?
Leukocytes are white blood cells produced primarily in the bone marrow, and their main function is to destroy bacteria, fungi, and other viruses. They transform toxic substances into harmless ones. In other words, they play an important role in the body’s defenses.
An adequate number of leukocytes must be “informed” about the presence of the infectious microorganism or foreign substance for them to be effective.
What disease causes an increase in white blood cells?
A high white blood cell count is often due to an inflammatory reaction or the body’s response to an infection. Thus, an increase or decrease in the number of white blood cells is often indicative of an underlying condition. It is the body’s first reaction when the body is attacked by a pathogen.
What causes low white blood cells?
A low white blood cell count can be a sign of infection or cancer. It can also be secondary to treatment such as chemotherapy.
What is a white blood cell count?
The blood formula is always associated with the blood count. It is carried out during a blood test and allows the cellular elements of the blood to be assessed in their qualitative aspect:
- morphology;
- homogeneity of shape and size of red blood cells and platelets;
- The percentage of each category of leukocytes (reduced to absolute value), polymorphonuclear cells, lymphocytes, and monocytes.
- It is also possible to detect possible cells normally absent from circulating blood (cells from the bone marrow). This test is very important in screening for many blood diseases.
A white blood cell count (WBC) is a test to assess the distribution of different white blood cells in order to diagnose an underlying problem affecting the immune system.
A blood test to assess the leukocyte count
This analysis is based on a blood test. Venous blood is usually collected from the crook of the elbow or a capillary at the tip of the finger. In newborns, the sample is taken using a lancet by pricking the heel.
The blood sample contains an anticoagulant. It is not necessary to fast. There are no special precautions to take when performing this blood test.
Why prescribe this test?
The assessment of different white blood cells contributes to the diagnosis of certain allergic, immune, and infectious diseases.
The leukocyte formula allows:
- to assess the human body’s ability to respond and fight infection;
- to reveal the presence of a bacterial or viral infection or an infestation by parasites,ord allergic reactions;
- to identify certain forms of leukemia or lymphoma.
This test is an integral part of the blood count, which is prescribed on many occasions.
Blood leukocyte count
To better understand the results of your analysis, it is important to understand that there are 5 main types of leukocytes (white blood cells) circulating in the blood. Produced in the bone marrow or the lymphoid system, they protect the body by recognizing and destroying infections, infestations, etc. Each of these white blood cells has different functions:
- Neutrophils are the most numerous. They eat microorganisms (phagocytose them) and hold them by producing toxic substances. They are on the front line against infections due to bacteria and fungi;
- Monocytes are also phagocytic cells, which are effective against bacterial or fungal infections.
- Eosinophilic polymorphonuclear leukocytes increase in case of allergic reactions and of parasitic infestations;
- Basophils control inflammation processes. They increase in certain blood pathologies and certain poisonings;
- Lymphocytes are the “killers” specific against infections and regulators of the immune response. We distinguish between B lymphocytes, which produce antibodies, and T lymphocytes, which direct the immune response and can directly kill specific microorganisms. Lymphocytes act against all types of viral or bacterial infections.
The white blood cell count will determine whether the proportion of these cells is normal or whether one of these types is increased or decreased, or whether abnormal or immature cells are present.
What is the normal white blood cell count for an adult?
The white blood cell count is normally between approximately 4000 and 10,000/mm3 of blood in men or women.
Leukopenia: What low white blood cell count is worrisome?
We speak of leukopenia when the number of white blood cells is less than 4000/mm3 of blood, and of leukocytosis when it is higher than the norm.
| Adult % | Absolute value/mm3 | |
| Polymorphonuclear Neutrophils | 50 – 80 | 2000 – 8000 |
| Polymorphonuclear Eosinophils | 1 – 4 | 40 – 400 |
| Basophils | 0 – 1 | 0 – 100 |
| Lymphocytes | 20 – 40 | 1000 – 4000 |
| Monocytes | 2 – 10 | 80 – 1000 |
What is the normal white blood cell count for a child?
| Child % | Absolute value/mm3 | |
| Polymorphonuclear Neutrophils | 40 – 60 | 2000 – 6000 |
| Polymorphonuclear Eosinophils | 1 – 4 | 100 – 500 |
| Basophils | 0 – 1 | 0 – 150 |
| Lymphocytes | 35 – 60 | 1500 – 7000 |
| Monocytes | 2 – 10 | 100 – 1500 |
Physiological variations
Values ​​and proportions vary with age. Certain environmental factors, such as stress, can affect certain parameters.
How to interpret the results?
The results express the percentage of each type of leukocyte present in the sample. Interpretation is based on absolute values: quantitatively and qualitatively.
Increased neutrophil counts (polynucleosis)
Neutrophils are increased in cases of bacterial infection, inflammatory disease, corticosteroid treatment, and, more rarely, leukemia.
Possible diagnoses
- Bacterial infections;
- Certain parasitic diseases;
- Inflammatory diseases;
- Ischemia, tissue necrosis (myocardial infarction, trauma);
- Cancers;
- Myeloproliferative syndromes;
- Hemorrhages and hemolysis;
- Some metabolic disorders: drop, uremia, eclampsia;
- Certain poisonings: benzene, radiation, certain medications;
Decreased neutrophil counts (neutropenia)
A decrease in neutrophils (< 1800/mm3) may result from a serious infection from taking medications, or chemotherapy.
Possible diagnoses
- Certain viral and bacterial infections: brucellosis, salmonellosis, hepatitis, HIV;
- Parasitosis:malaria, kala-azar;
- Associated with macrocytosis (increase in the size of macroocytes, a family of red blood cells) or with damage to other lines: perform a myelogram (acute leukemia, aplasia, agranulocytosis, myelodysplasia);
- Associated with spleen enlargement (large spleen): cirrhosis, parasitosis, sarcoidosis, storage disease, lymphoma
- Associated with an autoimmune condition: Felty’s syndrome, lupus erythematosus, rheumatoid arthritis;
- Anemia due to iron, folic acid, or vitamin B12 deficiency;
- Agranulocytosis of toxic or drug-induced, immunological, or constitutional origin;
Increased eosinophilic polymorphonuclear leukocytes (eosinophilia)
Eosinophils may be increased due to allergic problems, parasitic infestation, or skin conditions. More rarely, infections or various hematological malignancies may be involved.
Possible diagnoses
- allergic (asthma, eczema, various intolerances, etc.);
- Parasitosis (especially helminthiasis: worm parasitosis, taeniasis, distomatosis, strongyloidiasis, bilharzia, etc.);
- Hematopathies (Hodgkin, non-Hodgkin lymphoma);
- Certain autoimmune conditions;
- Dermatoses.
Increased basophils
Basophils may be increased in cases of leukemia, chronic inflammation, food hypersensitivity reactions, or following radiotherapy.
Possible diagnoses
- Myeloproliferative syndromes;
- Ulcerative colitis.
Increased lymphocytes (lymphocytosis)
Lymphocytes may be increased in cases of bacterial or viral infection, leukemia, lymphoma, or radiation therapy.
Possible diagnoses
-
- Physiological in children;
- Acute viral or bacterial infections (mononucleosis syndrome, viruses, whooping cough, Carl Smith disease);
- Endocrinopathies (thyrotoxicoses, etc.);
- Allergic drug reaction;
- Autoimmune disorders;
- Malignant lymphocytic hematopathy (chronic lymphocytic leukemia);
Decreased lymphocytes (lymphopenia)
Lymphocytes can be decreased with age, but also in cases of glucocorticoid treatment, stress, lupus, or HIV infection.
Possible diagnoses
- AIDS (CD4 collapse);
- Neoplastic diseases;
- Hodgkin;
- Sarcoidosis;
- Diabetic acidosis;
- Congenital alymphocytosis;
- Adrenal hyperfunction;
- Bone marrow aplasia;
- Toxic agranulocytosis;
- Corticosteroid therapy and immunosuppressive treatments;
- Extended irradiation;
- Congenital immune deficiencies.
Increased monocytes (monocytosis)
Monocytes can be increased in cases of leukemia, infections, or inflammatory syndrome, and more rarely in certain cancers.
Possible diagnoses
- Bacterial infections: brucellosis, salmonellosis, syphilis, leprosy, subacute endocarditis, tuberculosis;
- Parasitosis: malaria, leishmaniasis, trypanosomiasis, typhus, Rocky Mountain fever;
- Inflammatory syndromes: rheumatoid arthritis, systemic lupus erythematosus, ulcerative colitis, Crohn’s, sarcoidosis;
- Reactive monocytosis in the face of acute or chronic neutropenia (decrease in polymorphonuclear cells);
- Collagenosis, overload diseases;
- Malignant tumors undergoing lymphoplasmacytic proliferation: lymphoma, myeloma, Hodgkin;
- Leukemic monocytosis: chronic myelomonocytic leukemias, myeloproliferative syndromes, myelodysplasia, acute leukemia;
- Solid tumors (ovary, stomach, breast, melanoma);
- Prolonged treatment with high-dose corticosteroids;
- Presence of immature medullary elements;
- Myeloproliferative syndromes (myeloma);
- Erythroblastosis after splenectomy, severe hemolysis;
- Cancer metastases in the bone marrow;
- Blood blastosis in acute leukemia;
Decreased monocytes (monocytopenia)
Monocytes may be decreased in cases of bone marrow damage or certain forms of leukemia.
Possible diagnoses
- Bone marrow aplasia accompanies pancytopenia;
- Administration of corticosteroids;
- Hairy cell leukemia;
- After chemotherapy;
- Autosomal dominant and sporadic monocytopenia, with increased susceptibility to infections (mycobacteria, others) and myelodysplasias.
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