Neutrophils

Neutrophils are the most abundant type of white blood cells (WBCs) and play a critical role in the innate immune system by defending against bacterial and fungal infections.

Key Facts About Neutrophils

• Type: Granulocyte (contains enzyme-filled granules)
• Lifespan: Short-lived (~5–90 hours in blood, a few days in tissues)
• Produced in: Bone marrow
• Function: Rapid responders to infection—engulf and destroy pathogens (phagocytosis)

Role in Immunity

1. First Responders
   1. Quickly migrate to sites of infection (via chemotaxis).
2. Phagocytosis
   1. Engulf bacteria/fungi and kill them with:
   2. Reactive oxygen species (ROS)
      1. Enzymes (e.g., lysozyme, defensins)
3. Neutrophil Extracellular Traps (NETs)
   1. Release DNA nets to trap and kill microbes.

Normal Neutrophil Levels

• Absolute Neutrophil Count (ANC):
  • Normal: 1,500–8,000 cells/μL
  • Mild neutropenia: 1,000–1,500
  • Moderate neutropenia: 500–1,000
  • Severe neutropenia: <500 (high infection risk)

Causes of Low Neutrophils (Neutropenia)

1. Chemotherapy/Radiation (e.g., gemcitabine, carboplatin)
2. Bone Marrow Disorders (leukemia, aplastic anemia)
3. Severe Infections (sepsis, HIV)
4. Autoimmune Diseases (lupus, rheumatoid arthritis)
5. Vitamin Deficiencies (B12, folate)

Why Neutrophils Matter in Cancer Treatment

• Chemotherapy often causes neutropenia, increasing infection risk.
• Febrile neutropenia (fever + ANC <500) is a medical emergency.
• Growth factors (G-CSF, e.g., filgrastim) may be given to boost neutrophils.

Symptoms of Neutropenia

✔️ Fever (often the only sign of infection)
✔️ Sore throat, mouth ulcers
✔️ Frequent infections (pneumonia, skin abscesses)

How to Monitor Neutrophils

• Complete Blood Count (CBC) measures:
  • WBC count
  • Neutrophil %
  • ANC (Absolute Neutrophil Count) = WBC × (% neutrophils ÷ 100)

Example:

• If WBC = 2,000 and neutrophils = 20%, then ANC = 400 (severe neutropenia).

Management of Neutropenia

1. Prophylactic Antibiotics (if high risk)
2. G-CSF Injections (stimulate neutrophil production)
3. Infection Precautions
   1. Avoid raw foods, crowds, sick contacts.
   2. Practice strict hygiene.