Physiology · Blood, hemostasis and basic immunity
White blood cells: types and functions !
- Table to know
- Exam priority: medium
White blood cells are the body's defence team. Each type has a job: eat bacteria, fight parasites, make antibodies or kill infected cells.
Updated 2026-11-01
Also called: Leukocytes, White cell differential
See it in 3D: Spleen · Thymus · Hip bone
What it is
Leukocytes are nucleated blood cells that defend tissues; the blood is mainly their highway. They are counted in the complete blood count and sorted in the differential. Granulocytes (neutrophils, eosinophils, basophils) and monocytes are innate cells; lymphocytes carry out adaptive immunity.
Reference values (adults)
| Parameter | Value | Note |
|---|---|---|
| Total leukocytes | ≈4 500–11 000/µL | |
| Absolute neutrophils | ≈1 500–7 500/µL | <500/µL: high infection risk |
| Absolute lymphocytes | ≈1 000–4 000/µL |
Approximate values for a healthy adult at rest; each laboratory sets its own ranges.
The five leukocytes
| Cell | Share of white cells | Main job | Rises in |
|---|---|---|---|
| Neutrophil | ≈40–70 % | Phagocytosis and killing of bacteria and fungi | Bacterial infection, stress, glucocorticoids |
| Lymphocyte | ≈20–40 % | Adaptive immunity: B (antibodies), T (helper, cytotoxic), NK | Viral infection, pertussis, chronic lymphocytic leukemia |
| Monocyte | ≈2–8 % | Becomes macrophage or dendritic cell; presents antigen | Chronic infection (tuberculosis), recovery phase |
| Eosinophil | ≈1–4 % | Attacks parasites; modulates allergy | Helminths, asthma and allergy, adrenal insufficiency |
| Basophil | ≈0.5–1 % | Releases histamine and heparin | Allergy, chronic myeloid leukemia |
Clinical notes
- Dengue typically causes leukopenia with thrombocytopenia, a useful early clue in Colombia.
- HIV destroys CD4⁺ helper T cells; the CD4 count falls while the total white count may look ordinary.
- Leukocyte adhesion deficiency (integrin defect): high blood neutrophils, no pus, delayed separation of the umbilical cord.
Test yourself
Think of the answer, then tap the question to see it.
Why does a patient given glucocorticoids show a high neutrophil count without infection?
Glucocorticoids reduce adhesion molecules, so neutrophils in the marginated pool detach from vessel walls into the circulating pool, and marrow release rises; it is a redistribution, not an infection.
What does a 'left shift' mean on a differential count?
More immature neutrophils (bands, sometimes metamyelocytes) in blood, because the marrow releases cells early under strong demand, typically bacterial infection or sepsis.
A child has high blood neutrophils, recurrent infections without pus and delayed umbilical cord separation. Which step of leukocyte migration fails?
Firm adhesion: β2-integrins (CD18) cannot bind ICAM-1, so neutrophils roll but never leave the vessel to reach the tissue.
See it in 3D
The structures of Durgical's 3D anatomy where it happens.
Related topics
Related conditions
Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.
Sources: 18.4 Leukocytes and Platelets (OpenStax (Rice University), 2022); Complete Blood Count (CBC) (MedlinePlus (U.S. National Library of Medicine), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 34). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).
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