Author
Bowtie Team
Updated on
2026-01-08
Disclaimer: This article is translated with the assistance of AI.
White blood cells play a crucial role in the immune system, acting as the body’s first line of defense against diseases. High or low levels can negatively affect health. The Bowtie Medical Information Team breaks down their main functions, classifications, normal values, abnormal causes, and dietary recommendations.
Functions of White Blood Cells
White blood cells play a crucial role in the immune system, primarily functioning to protect the body from pathogens or infections. They are responsible for identifying, engulfing, and destroying invading bacteria, viruses, and other harmful substances 1 . As white blood cells circulate through the blood, they detect infected areas and gather other white blood cells to help defend the body against unknown pathogens such as bacteria or viruses. Antigens in white blood cells attach to the surfaces of pathogens and other foreign substances, allowing white blood cells to detect and initiate defensive immune responses, such as engulfing bacteria, within minutes to prevent pathogen invasion 2 .
Certain white blood cells, such as neutrophils, macrophages, and dendritic cells, have phagocytic capabilities, enabling them to actively identify, surround, and engulf pathogens in a process known as phagocytosis 3 . During this process, phagocytic cells first bind to pathogens via receptors on their surface, then enclose the pathogens to form phagosomes. The phagosomes subsequently fuse with lysosomes, releasing enzymes and reactive oxygen species that degrade and digest the pathogens 1 .
Classification and Characteristics of White Blood Cells
Granulocytes
Granulocytes in the blood can be divided into neutrophils, eosinophils, and basophils 4 :
| Neutrophils | Eosinophils | Basophils | |
| Overview and Functions | Neutrophils are the most abundant granulocytes, making up about two-thirds of all white blood cells.
Each neutrophil can engulf up to 20 bacteria during its lifetime. |
Eosinophils are involved in nearly all immune responses, most notably allergic reactions, and help combat parasites. | Basophils primarily counter allergic reactions by releasing histamine (to expel allergens from the body) and heparin (to prevent blood clotting). |
| Role in the Immune System | Neutrophils have phagocytic functions; they attack bacteria and act as antigen-presenting cells (APCs), serving as the body’s first line of defense against bacterial infections. | Eosinophils possess phagocytic functions and contain eosinophilic granules that are toxic to parasites; they also neutralize allergens released by mast cells, providing a defense against parasitic infections and allergies. | Basophils have IgE receptors on their surface; when allergens bind to IgE, it triggers degranulation, releasing histamine to produce allergic reactions. |
Agranulocytes
Agranulocytes among white blood cells include lymphocytes and monocytes. Lymphocytes are mainly divided into B cells, T cells, and natural killer cells, which participate in immune responses; monocytes, upon leaving blood vessels, transform into macrophages with phagocytic abilities and can present pathogen antigens to T cells, accelerating immune reactions 5 :
- B cells: They produce antibodies that can bind to pathogens, helping to clear infections.
- T cells: These include CD4+ T cells (helper T cells) and CD8+ T cells (cytotoxic T cells), which can kill cells infected by viruses.
- Natural killer cells: They can directly kill cells infected by viruses, primarily by identifying infected, foreign, or abnormal cells and rapidly destroying them without prior exposure to the pathogen, including infected or cancerous cells.
- Monocytes: Monocytes originate in the bone marrow and exist as monocytes in blood vessels; outside vessels, they become macrophages. Their roles in the immune system include replenishing macrophages and dendritic cells under normal conditions, and rapidly gathering at infected tissues during inflammation to differentiate into macrophages and dendritic cells, triggering immune responses.
White Blood Cell Count
Normal Values
According to the Leukemia & Lymphoma Society 6 , the white blood cell count for adults and children should be:
| White Blood Cell Count | |
| Adult Males | 5,000 – 10,000/μL |
| Adult Females | 4,500 – 11,000/μL |
| Children | 5,000 – 10,000/μL |
White blood cell counts can be influenced by various factors, including lifestyle habits, medications, and underlying diseases. Nationality and age can also cause differences; for instance, children under 4 years old typically have higher white blood cell counts than adults, and the numbers gradually decline with age. Certain infectious diseases are more common in specific regions, which may affect local residents’ white blood cell counts 1 .
Dietary habits and lifestyles associated with different nationalities can also impact the immune system, thereby affecting white blood cell counts 1 . Regular blood tests to check white blood cell counts can help detect abnormalities early, allowing for timely diagnosis and treatment of potential health issues, such as infections, inflammation, or blood disorders.
Potential Impacts of Abnormal Values
Both high and low white blood cell counts are abnormal and can negatively affect health. Leukopenia refers to a low white blood cell count, while leukocytosis indicates a high count. Elevated white blood cells are often linked to infections, inflammation, or conditions like cancer and leukemia 7 , whereas low counts can weaken the immune system, making the body more susceptible to bacterial or viral infections, which can even be life-threatening in severe cases 7 .
Regular health check-ups, including blood tests for white blood cell counts, are essential to identify abnormalities early and address potential health problems, such as infections, inflammation, or blood disorders.
There is a lot of online information about high and low white blood cell counts, but it is not advisable to self-diagnose based on this alone. Individuals with abnormal blood results should seek professional medical advice for further examinations and a definitive diagnosis 2 .
How Does Bowtie Insurance Provide Coverage?
High or low white blood cell counts may be related to pneumonia, encephalitis, leukemia, Bowtie Term CI can provide financial assistance if you lose your job due to a critical illness,
Bowtie Pink can offer first-dollar coverage for medical expenses, with eligible medical expenditures fully reimbursed* and get a quote now.
- * The Bowtie Pink series provides full reimbursement for eligible medical expenses such as diagnosis, hospitalization, surgery, and specified non-surgical cancer treatments (excluding the US), subject to annual and lifetime coverage limits. Compensation amounts may be adjusted if claims involve hospitals in mainland China outside the designated list, high-end hospitals within the designated list in mainland China, rooms exceeding the specified ward level, or pre-existing conditions.
Causes and Symptoms of Abnormal White Blood Cell Counts
Causes and Symptoms of High White Blood Cell Counts
Leukocytosis, or an excess of white blood cells, is commonly caused by 7 :
- Smoking
- Infections such as chickenpox, measles, scarlet fever, tuberculosis, syphilis, or whooping cough
- Tissue necrosis due to injuries, burns, or other physical trauma
- Allergies and autoimmune diseases, such as drug allergies, bronchial asthma, or allergic skin conditions
- Menstrual period, ovulation, late pregnancy, or childbirth in women
- Emotional stress or pressure
- Certain medications like corticosteroids
- Bone marrow tumors, leukemia, and other cancers
Symptoms that may result from leukocytosis include 3 :
- Fever
- Pain
- Easy bruising
- Shortness of breath
- Itchy skin
- Weight loss
- Sweating (especially at night)
Causes and Symptoms of Low White Blood Cell Counts
Leukopenia, or a deficiency of white blood cells, is commonly caused by 7 :
- Liver damage, including that caused by excessive alcohol consumption
- Severe infections
- Enlarged or damaged spleen
- Autoimmune diseases
- Diseases that damage bone marrow function, such as bone marrow fibrosis or damage
- Certain medications, including chemotherapy and antibiotics
- Viral infections such as influenza, viral hepatitis, chickenpox, or rubella
- Prolonged exposure to radiation
Symptoms that may result from leukopenia include 3 :
- Bone pain throughout the body
- Fever
- Chills
- Headaches
- Dizziness
- Weakness and fatigue in the limbs
- Loss of appetite
- Insomnia
Dietary Recommendations for Low White Blood Cells
Consuming certain foods may help adjust low white blood cell issues 8 . However, if you find abnormal white blood cell indices, it is still recommended to seek medical attention as soon as possible to determine the cause of the abnormality and receive medical follow-up. The following dietary recommendations are only supplementary and cannot replace the treatment advice of professional healthcare professionals:
- Foods rich in Vitamin C: Oranges, kiwifruit, grapefruit, lemons
- Vitamin B12: Fresh fish such as tuna or mackerel, eggs, organ meats like pork liver
- Foods rich in folic acid: Green leafy vegetables such as spinach, legumes
- Foods rich in zinc: Nuts and seeds such as sesame or peanuts, lean meat, seafood
- High-protein foods: Fish, chicken, beef, pork, eggs, legumes, dairy products, etc.
Sources
- 1 Complete Blood Count (CBC).” Mayoclinic, 14 Jan. 2023,
- 2 “White Blood Cells.” Clevelandclinic, 23 July 2021,
- 3 “Phagocytosis.” Medlineplus, 31 Mar. 2024,
- 4 Granulocytes.” Clevelandclinic, 8 July 2024,
- 5 Agranulocyte. 2019,
- 6 Understanding Blood Counts.
- 7 CBC Blood Test (Complete Blood Count). 28 Sept. 2022,
- 8 15 Foods That Boost the Immune System.” Healthline, 24 May 2025,
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