On this page
Introduction
Neutrophils are the most abundant type of white blood cells with multi-lobed nuclei and cytoplasmic granules. They are the first responders of innate immunity and form the front line of defense against bacterial infections.
In this article you will learn the structure of neutrophils, forms including segmented and band neutrophils, how Absolute Neutrophil Count (ANC) is calculated, normal range in cells per mm3 and percentage, causes of low neutrophils or neutropenia and high neutrophils or neutrophilia, and key functions including phagocytosis, degranulation, and Neutrophil Extracellular Traps (NETs).
What are Neutrophils?
Definition and Prevalence
Neutrophils are a type of granulocyte with multi-lobed nuclei and stainable cytoplasmic granules. They are the most abundant granulocytes, occupying about 40-60% of total white blood cells in adults and about 60-70% of circulating immune cells. Along with eosinophils and basophils, they belong to polymorphonuclear leukocytes.
Formation and Lifespan
Like all blood cells, neutrophils are formed from hematopoietic stem cells in the bone marrow through granulopoiesis. After differentiation, they are released into peripheral blood and circulate for 7 to 10 hours in circulation, before migrating into tissues where lifespan is 1-3 days, up to few days during inflammation. They are highly motile, allowing rapid movement in and out of vessels by diapedesis during infection.
New neutrophils are continuously produced in bone marrow, about 10^11 cells per day in adults.
Neutrophil Structure
Size and Shape
Neutrophils are mostly circular in blood smear, ranging 10-12 µm in diameter in peripheral smear, around 7-9 µm in suspension. Average size in humans is often reported around 8.85 µm in automated measurements. Shape changes to amoeboid once activated, extending pseudopodia to attack invaders.
Nucleus
Characteristic multi-lobed nucleus with 2-5 lobes, typically 3 lobes in mature cells, joined by slender chromatin filament. This segmentation distinguishes mature neutrophils from band forms. Nucleolus is present in young neutrophil precursors like myelocytes but is lost as neutrophil matures. Chromatin becomes more condensed with maturation.
Cytoplasmic Granules
Cytoplasm contains large number of granules essential for microbicidal activity. Three main types:
Primary or Azurophilic Granules
First to appear, purple-colored, contain myeloperoxidase, defensins, lysozyme, bactericidal permeability increasing protein. Have potent microbicidal activity, fuse with phagosomes.
Secondary or Specific Granules
Second type, smaller, contain lysozyme, collagenase, lactoferrin, NADPH oxidase components, complement activators. Important for extracellular killing and inflammation.
Tertiary or Gelatinase Granules and Secretory Vesicles
Contain gelatinase, acetyltransferase, and surface receptors like CD11b/CD18 needed for adhesion and migration. Easily mobilized during early activation.
Other Cytoplasmic Organelles
Other organelles like mitochondria and Golgi complex appear sparingly, and rough endoplasmic reticulum is essentially absent in mature neutrophils as they are terminally differentiated and have limited protein synthesis.
Forms of Neutrophil
Mature Segmented vs Immature Band Forms
In routine differential count, neutrophils are divided into:
- Segmented or mature neutrophils: Nucleus with 3-5 distinct lobes. Most abundant in circulation.
- Band neutrophils or stab cells: Nucleus horse-shoe or band-shaped without clear segmentation, representing immature forms recently released from marrow. Normal bands 0-5%. Increase in bands indicates left shift in acute infection.
Functional Subsets: Killer vs Cager and N1/N2
Original content mentioned neutrophil-killers and neutrophil-cagers. This is not a standard textbook classification but reflects emerging concept of functional heterogeneity.
- Neutrophil-killers: Classic phagocytic and microbicidal subset performing direct killing via phagocytosis, degranulation, and oxidative burst.
- Neutrophil-cagers: Described as transport subset delivering foreign particles to target site for action of killer neutrophils. In modern literature, similar roles are attributed to cooperative neutrophil swarming and antigen shuttling.
Current research also classifies tumor-associated neutrophils as N1 anti-tumor and N2 pro-tumor, analogous to M1/M2 macrophages, with pro- and anti-tumor activities.
Neutrophils Test / Absolute Neutrophil Count
ANC Formula
Absolute Neutrophil Count (ANC) measures number of neutrophils and other granulocytes present in blood sample. Test detects total WBCs including mature and immature neutrophils.
Blood count breaks down neutrophils into segmented or mature neutrophils and immature neutrophils or bands.
Formula:
ANC (cells/mm3) = [(% Segmented neutrophils + % Bands) / 100] x Total WBC count (cells/mm3)
Or simply:
ANC = Absolute mature neutrophils + Absolute immature neutrophils
Example: If WBC 8000/mm3, segmented 50%, bands 5%, then ANC = (55/100) x 8000 = 4400 cells/mm3.
When is Test Performed?
Test is performed to detect infection, monitor immune status during chemotherapy, evaluate bone marrow function, and as part of complete blood count (CBC). It helps determine risk of infection when ANC is low and detects inflammatory response when high.
Neutrophils Normal Range
In Terms of Cell Count
Normal range may vary slightly by age, sex, ethnicity, and lab method. Generally accepted adult ranges:
- ANC count in adults: 1500-8000 cells/mm3 or 1.5-8.0 x 10^9/L
- Mature segmented neutrophils: 2500-6000 cells/mm3
- Immature bands: 0-500 cells/mm3
Neonates have higher counts.
In Terms of Percentage of WBC
- ANC percentage: 40-70% of total WBCs in adults, commonly quoted 40-60%
- Mature segmented neutrophils: 40-60%
- Immature neutrophils or bands: 0-5%
Table for quick reference:
|
Parameter |
Normal Count (cells/mm3) |
Normal Percentage |
|---|---|---|
|
Total ANC |
1500-8000 |
40-70% |
|
Segmented neutrophils |
2500-6000 |
40-60% |
|
Bands |
0-500 |
0-5% |
Neutrophils Low - Neutropenia
Definition and Grading
When neutrophil level is less than 1500 cells/mm3, it is considered low. This condition is termed neutropenia.
- Mild neutropenia: 1000-1500 cells/mm3
- Moderate neutropenia: 500-1000 cells/mm3
- Severe neutropenia: <500 cells/mm3, high risk for severe infection
- Agranulocytosis: <200 cells/mm3
Causes of Low Neutrophil Count
Low count is often observed with medication intake but can be sign of other illness.
- Drugs: Chemotherapy, clozapine, carbimazole, antibiotics like chloramphenicol, anticonvulsants
- Suppressed marrow: Aplastic anemia, cancer infiltration, myelodysplastic syndrome, bone marrow diseases
- Immune-mediated destruction: Autoimmune diseases like lupus, rheumatoid arthritis, Crohn's disease, Felty syndrome
- Infections: AIDS, tuberculosis, hepatitis, viral infections like influenza, EBV
- Nutritional deficiencies: Vitamin B12, folate, copper deficiency
- Hypersplenism: Increased sequestration in enlarged spleen
- Congenital: Cyclic neutropenia, Kostmann syndrome
Neutrophils High - Neutrophilia
Definition
When neutrophils greater than 8000 cells/mm3 or >7000 cells/mm3 depending on lab, it is considered high. Termed neutrophilia. Mild, occasional neutrophilia to severe condition termed neutrophilic leukocytosis or leukemoid reaction.
Causes of High Neutrophil Count
Because neutrophils are part of immune system, increase is primarily due to infection but also other factors.
- Bacterial infections: Especially pyogenic infections resulting in inflammation, left shift with bands
- Inflammation: After heart attacks, burns, tissue necrosis, inflammatory disorders
- Stress and hormones: Increased cortisol, adrenaline, physical stress, exercise
- Drugs: Corticosteroids like prednisone, lithium, epinephrine cause demargination
- Malignancy: Leukemia, myeloproliferative neoplasms, paraneoplastic leukemoid reaction
- Surgical procedures: Splenectomy, appendicitis, surgery
- Smoking and metabolic: Chronic smoking, diabetic ketoacidosis
Neutrophils Functions
Neutrophils are most abundant granulocytes making up about 40% of white blood cells and about 60% of immune cells in blood.
Phagocytosis
Neutrophils are first responders to infection. They recognize, engulf, and phagocytose bacteria into phagosomes, which fuse with granules to form phagolysosomes before hydrolyzing and destroying them via oxidative burst mediated by NADPH oxidase producing reactive oxygen species.
Degranulation and Antimicrobial Proteins
Cells secrete range of proteins that have antimicrobial effects as well as tissue remodeling potential. Primary granules release myeloperoxidase forming hypochlorous acid. Secondary granules release lactoferrin chelating iron and lysozyme degrading bacterial wall.
NETs Formation
Recently discovered function is formation of Neutrophil Extracellular Traps (NETs). Activated neutrophils extrude decondensed chromatin decorated with antimicrobial proteins to trap and kill extracellular bacteria, fungi, and viruses. Important but excessive NETs contribute to tissue damage and thrombosis.
Neutrophil Recruitment Pathway
Recruitment involves multistep cascade:
- Rolling: Selectins on endothelium interact with neutrophil ligands
- Activation: Chemokines like IL-8, complement C5a activate integrins
- Firm adhesion: Integrins CD11b/CD18 bind ICAM-1
- Transmigration: Diapedesis through endothelium into tissue
- Chemotaxis: Migration towards pathogen via chemokine gradient
Neutrophils have short lifespan and destroy themselves during degradation of invaders. New neutrophils are continuously produced in marrow.
Interactions Between Neutrophils and Macrophages
Neutrophils and macrophages cooperate. Neutrophils initiate acute inflammation, recruit monocytes which become macrophages. Macrophages clear apoptotic neutrophils via efferocytosis, releasing anti-inflammatory cytokines like IL-10 and TGF-beta to resolve inflammation. Dysregulation leads to chronic inflammation.
Key Takeaways
- Neutrophils are most abundant granulocytes, 40-70% of WBCs, 10-12 µm in smear, with 2-5 lobed segmented nucleus and azurophilic and specific granules containing myeloperoxidase, defensins, lysozyme, lactoferrin.
- Formed from hematopoietic stem cells in bone marrow, circulate 7-10 hours, tissue lifespan 1-3 days, about 10^11 produced daily.
- Forms include mature segmented neutrophils and immature bands; left shift with increased bands indicates acute bacterial infection; functional subsets include killer vs cager concept and N1/N2 in cancer.
- Absolute Neutrophil Count ANC = (% segmented + % bands)/100 x WBC count; normal ANC 1500-8000 cells/mm3 or 1.5-8.0 x10^9/L, bands 0-5%.
- Neutropenia <1500 cells/mm3 graded mild 1000-1500, moderate 500-1000, severe <500, agranulocytosis <200; causes include chemotherapy drugs, marrow failure, infections like AIDS/TB, B12/folate deficiency, autoimmune diseases like lupus and rheumatoid arthritis.
- Neutrophilia >8000 cells/mm3 caused by pyogenic bacterial infections, inflammation post MI or burns, stress hormones cortisol and adrenaline, drugs like prednisone, leukemia, splenectomy and smoking.
- Key functions are phagocytosis with phagolysosome formation and oxidative burst, degranulation releasing antimicrobial proteins, and NETs formation trapping extracellular pathogens; recruitment involves rolling, activation, adhesion, transmigration and chemotaxis.
- Interaction with macrophages: neutrophils initiate inflammation and recruit monocytes, macrophages clear apoptotic neutrophils to resolve inflammation.
Scientific References
- Hoffbrand AV, Moss PAH → Hoffbrand's Essential Haematology → 8th Edition → Wiley Blackwell → Chapter 18 White cells – Granulocytes and monocytes – neutrophil morphology and kinetics.
- Bain BJ → Blood Cells: A Practical Guide → 5th Edition → Wiley Blackwell → Chapter 2 Morphology of granulocytes, segmented and band neutrophils.
- Kumar V, Abbas AK, Aster JC → Robbins and Cotran Pathologic Basis of Disease → 10th Edition → Elsevier → Chapter 3 Inflammation and Repair – Neutrophil recruitment and function.
- Abbas AK, Lichtman AH, Pillai S → Cellular and Molecular Immunology → 10th Edition → Elsevier → Chapter 4 Innate Immunity – Neutrophil functions, phagocytosis.
- Parham P → The Immune System → 5th Edition → Garland Science → Chapter 2 Innate Immunity – Neutrophils and granulocytes.
- NCERT → Biology Textbook for Class XI → Reprint 2023-24 → National Council of Educational Research and Training, India → Chapter 18 Body Fluids and Circulation – White blood cells.
- Borregaard N → Neutrophils, from marrow to microbes → Immunity → 2010 → Volume 33, Issue 5, Pages 657-670 → DOI: 10.1016/j.immuni.2010.11.011
- Mayadas TN, Cullere X, Lowell CA → The multifaceted functions of neutrophils → Annual Review of Pathology: Mechanisms of Disease → 2014 → Volume 9, Pages 181-218 → DOI: 10.1146/annurev-pathol-020712-164023
- Brinkmann V, Zychlinsky A → Neutrophil extracellular traps: is immunity the second function of chromatin? → Journal of Cell Biology → 2012 → Volume 198, Issue 5, Pages 773-783 → DOI: 10.1083/jcb.201203170
- Kolaczkowska E, Kubes P → Neutrophil recruitment and function in health and inflammation → Nature Reviews Immunology → 2013 → Volume 13, Issue 3, Pages 159-175 → DOI: 10.1038/nri3399
- Rosales C → Neutrophil: A Cell with Many Roles in Inflammation or Several Cell Types? → Frontiers in Physiology → 2018 → Volume 9, Article 113 → DOI: 10.3389/fphys.2018.00113
- National Center for Biotechnology Information → StatPearls – Neutropenia – Absolute Neutrophil Count → URL: https://www.ncbi.nlm.nih.gov/books/NBK570571/ → Accessed 2025-2026
- National Library of Medicine → MedlinePlus – Absolute Neutrophil Count Lab Test → URL: https://medlineplus.gov/lab-tests/absolute-neutrophil-count/ → Accessed 2025-2026
- American Society of Hematology → Blood Education – Neutropenia and Neutrophilia → URL: https://www.hematology.org/education/patients/blood-disorders → Accessed 2025-2026
- Centers for Disease Control and Prevention → Complete Blood Count – Reference and Interpretation → URL: https://www.cdc.gov/nchs/data/nhanes/nhanes_07_08/cbc_e_met_complete_blood_count.pdf → Accessed 2025-2026