Eosinophils
Eosinophils are a type of white blood cell that helps the body fight infections and allergies. They play an important role in the immune system by attacking harmful invaders and controlling inflammation. Here we will discuss about Eosinophils definition, structure, function and its related disorders.
What Are Eosinophils?
Eosinophils are a kind of white blood cell that comes from the bone marrow. They move into the blood and then go to different tissues in the body. These cells contain tiny granules filled with chemicals that help fight infections and regulate immune responses.
What Do Eosinophils Do?
Eosinophils have several important jobs, including:
- Fighting Parasites: They help kill worms and other parasites that enter the body.
- Causing Allergic Reactions: Eosinophils play a role in conditions like asthma and allergies by releasing chemicals that cause inflammation.
- Helping with Inflammation: They help control inflammation, which is the body’s way of responding to injury or infection.
- Healing Wounds: Eosinophils help repair damaged tissue after infections or injuries.
Structure of Eosinophils
Eosinophils have a distinct structure that helps them perform their functions:
- Size: They are about 12–17 micrometers in diameter, making them slightly larger than red blood cells.
- Nucleus: They have a bilobed nucleus, meaning it has two connected lobes that look like a dumbbell under a microscope.
- Cytoplasm: Their cytoplasm contains numerous large, reddish-orange granules, which store enzymes and proteins involved in immune responses.
- Granules: These granules contain:
- Major Basic Protein (MBP): Helps kill parasites and contributes to allergic reactions.
- Eosinophil Cationic Protein (ECP): Plays a role in inflammation and cell damage.
- Eosinophil Peroxidase (EPO): Helps in the destruction of pathogens.
- Eosinophil-Derived Neurotoxin (EDN): Has antiviral properties.
- Surface Receptors: Eosinophils have receptors for different signals, such as:
- Interleukin-5 (IL-5): Stimulates eosinophil production.
- Immunoglobulin E (IgE): Important for allergic reactions.
- Chemokine Receptors: Help eosinophils move to sites of infection or inflammation.
Eosinophil Count and What It Means?
Doctors can check eosinophil levels through a blood test. Normally, people have 0 to 500 eosinophils per microliter (cells/μL) of blood. If the number is too high or too low, it may indicate a health problem.
High Eosinophil Count (Eosinophilia)
When eosinophil levels go above 500 cells/μL, it is called eosinophilia. This can be:
- Mild (500–1,500 cells/μL) – Often linked to allergies or mild infections.
- Moderate (1,500–5,000 cells/μL) – May indicate a more serious problem.
- Severe (>5,000 cells/μL) – Could be a sign of a major health issue.
Causes of High Eosinophils:
- Parasitic Infections (e.g., worms)
- Allergies (e.g., asthma, hay fever, eczema)
- Autoimmune Diseases (e.g., some rare inflammatory conditions)
- Certain Medications (e.g., antibiotics, pain relievers)
- Cancers (e.g., leukemia, lymphoma)
Low Eosinophil Count (Eosinopenia)
Low eosinophil levels are not very common but may happen due to:
- Severe Infections
- Stress or Steroid Medications
- Cushing’s Syndrome (a rare hormone disorder)
How Doctors Check Eosinophils
Lab tests used to check eosinophil levels include:
- Complete Blood Count (CBC) with Differential – Shows the percentage of eosinophils in the blood.
- Absolute Eosinophil Count (AEC) – Measures the exact number of eosinophils in the blood.
- Tissue Biopsy – Checks for eosinophils in specific tissues, like the esophagus or lungs.
Health Problems Linked to Eosinophils
- Eosinophilic Esophagitis (EoE): A condition where eosinophils build up in the food pipe, causing swallowing problems.
- Hypereosinophilic Syndrome (HES): A rare disease where too many eosinophils damage organs.
- Chronic Eosinophilic Pneumonia: A lung disease that causes breathing issues due to too many eosinophils in the lungs.
