🩺 Definition
White blood cells (WBCs), also known as leukocytes, are one of the main components of blood. They are responsible for defending the body against infections, viruses, bacteria, parasites, and even abnormal (cancerous) cells.
Unlike red blood cells, WBCs do not carry oxygen — their main job is to maintain the immune system.
📌 Key Facts
| Feature | Details |
|---|---|
| Scientific Name | Leukocytes (from Greek leukos = white, kytos = cell) |
| Appearance | Colorless (appear white under a microscope) |
| Lifespan | A few hours to several days or weeks (depending on the type) |
| Production Site | Bone marrow and lymphatic system |
| Normal Count | 4,000–11,000 WBCs per microliter of blood (varies slightly by lab) |
| Function | Immune defense: fighting infection, inflammation, foreign bodies |
🔬 Types of White Blood Cells
WBCs are classified into two main categories based on their structure:
1. Granulocytes (contain granules in their cytoplasm)
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Neutrophils – First responders to bacterial infection
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Eosinophils – Fight parasites, involved in allergies
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Basophils – Release histamine during allergic responses
2. Agranulocytes (no granules)
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Lymphocytes – Include B-cells (antibody production) and T-cells (cellular immunity)
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Monocytes – Become macrophages and eat pathogens & dead cells
🧬 Function Overview
| Type | Main Function |
|---|---|
| Neutrophils | Destroy bacteria and fungi |
| Lymphocytes | Fight viral infections, produce antibodies |
| Monocytes | Clean up dead cells, engulf pathogens |
| Eosinophils | Fight parasites, mediate allergic reactions |
| Basophils | Release chemicals like histamine in allergic responses |
🧪 White Blood Cell Count & Tests
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A Complete Blood Count (CBC) measures WBC levels.
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High WBC count may indicate: infection, inflammation, leukemia.
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Low WBC count may indicate: bone marrow issues, autoimmune diseases, chemotherapy effects.
📚 Etymology & Origin
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Leukocyte comes from the Greek words:
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Leukos (λευκός) = "white"
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Kytos (κύτος) = "cell"
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First discovered and studied in the mid-1800s.
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Paul Ehrlich, a German scientist, contributed significantly to classifying WBC types based on staining.
⚠️ Disorders Related to WBCs
| Disorder | Description |
|---|---|
| Leukopenia | Abnormally low WBC count |
| Leukocytosis | Abnormally high WBC count |
| Leukemia | Cancer of white blood cells |
| Lymphoma | Cancer of the lymphatic system (includes WBCs) |
🧠 Summary
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White blood cells are vital defenders in your immune system.
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They’re produced in the bone marrow and travel in the blood and lymph.
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There are different types of WBCs, each with specialized roles.
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Their count and balance are essential indicators of your health