White blood cell
White blood cell (WBC), also known as a leukocyte, is a type of blood cell involved in protecting the body against infections, diseases, and foreign substances. White blood cells are important components of the immune system and help defend the body from bacteria, viruses, fungi, parasites, and abnormal cells. :contentReference[oaicite:0]{index=0}
White blood cells are produced mainly in the bone marrow and circulate through the bloodstream and lymphatic system. Unlike red blood cells, white blood cells contain a nucleus. :contentReference[oaicite:1]{index=1}
Overview
White blood cells protect the body through immune responses and pathogen destruction.
The immune defense process can be represented as:
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White blood cells help identify and eliminate harmful microorganisms and damaged cells. :contentReference[oaicite:3]{index=3}
Formation
White blood cells are formed through a process called leukopoiesis in the bone marrow.
The developmental pathway can be represented as:
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All white blood cells originate from hematopoietic stem cells. :contentReference[oaicite:5]{index=5}
Types of White Blood Cells
White blood cells are generally divided into granulocytes and agranulocytes.
Granulocytes
Granulocytes contain granules in their cytoplasm.
Types include:
- Neutrophils
- Eosinophils
- Basophils
Neutrophils are the most abundant white blood cells and play major roles in phagocytosis. :contentReference[oaicite:6]{index=6}
Agranulocytes
Agranulocytes do not contain visible cytoplasmic granules.
Types include:
- Lymphocytes
- Monocytes
Lymphocytes include B cells and T cells that support adaptive immunity. :contentReference[oaicite:7]{index=7}
Functions
Major functions of white blood cells include:
- Fighting infections
- Destroying pathogens
- Producing antibodies
- Supporting inflammation
- Removing damaged cells
- Immune regulation
Some white blood cells perform phagocytosis to engulf harmful particles. :contentReference[oaicite:8]{index=8}
White Blood Cells and Immunity
White blood cells are central to both innate and adaptive immunity.
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Innate immune cells provide rapid defense, while adaptive immune cells provide targeted and long-term immune responses. :contentReference[oaicite:10]{index=10}
Normal White Blood Cell Count
Healthy adults generally have approximately 4,500 to 11,000 white blood cells per cubic millimeter of blood. :contentReference[oaicite:11]{index=11}
White blood cell count may increase during infections or inflammation.
White Blood Cell Disorders
Abnormal white blood cell levels may indicate disease.
Leukocytosis
An abnormally high white blood cell count.
Possible causes include:
- Infection
- Inflammation
- Leukemia
Leukopenia
An abnormally low white blood cell count.
Possible causes include:
- Bone marrow disorders
- Immune deficiency
- Certain medications
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Clinical Importance
White blood cells are commonly examined using blood tests such as the complete blood count (CBC). Changes in white blood cell count may help diagnose infections, immune disorders, inflammation, and blood cancers. :contentReference[oaicite:13]{index=13}
Importance
White blood cells are essential for survival because they protect the body from harmful microorganisms and help maintain immune balance and tissue health. :contentReference[oaicite:14]{index=14}