**Eosinophils and Type-2 Inflammation:

December 4, 2025
|In Immune System
|By GAtherton

What Aspergillosis Patients Need to Know**

Part of the Aspergillosis Immune System Knowledge Hub

Eosinophils are a type of white blood cell central to allergy, asthma, and ABPA. They play a major role in symptoms, flare-ups, mucus plugging, and treatment responses.

This article explains eosinophils in simple terms.

🧬 1. What Are Eosinophils?

Eosinophils are immune cells filled with granules containing powerful enzymes.
They normally help:

  • fight parasites

  • regulate allergic inflammation

  • repair tissues

  • produce important immune signals

But in excess, they can cause damage — especially in the lungs.

🔥 2. Eosinophils in the Lungs

Activated eosinophils release their granules into airway tissues, causing:

  • swelling

  • increased mucus

  • airway narrowing

  • cough sensitivity

  • wheezing

  • breathlessness

This makes them key players in allergic and fungal-related lung disease.

🌟 3. Eosinophils in ABPA

Eosinophils are highly active in ABPA.

ABPA involves a strong “type-2” allergic response to Aspergillus, including:

  • high IgE

  • mast cell activation

  • large numbers of eosinophils

  • thick, sticky mucus

  • airway obstruction

  • repeated flare-ups

Eosinophils contribute significantly to long-term lung damage if not controlled.

🌬 4. Eosinophils in Severe Asthma and SAFS

In severe or allergic asthma:

  • eosinophils can be persistently high

  • they drive airway swelling

  • they increase sensitivity to triggers

  • they worsen recovery after infection

In SAFS, eosinophils may be moderately raised but symptoms can still be severe.

🦠 5. Eosinophils in CPA

In CPA, eosinophils are not usually the dominant cell, but they still matter when patients also have:

  • asthma

  • ABPA overlap

  • fungal allergy

  • airway hypersensitivity

  • steroid withdrawal flare-ups

🔗 6. How Eosinophils Link to Other Immune Cells

They interact with:

  • IgE → recruits eosinophils

  • T-helper cells (Th2) → tell bone marrow to make more

  • Mast cells → release histamine that pulls eosinophils into tissues

  • Airway lining cells → release distress signals

This is why severe allergic pathways often involve all three:
IgE → mast cells → eosinophils

💊 7. Treatments That Target Eosinophils

✔ Steroids (oral or inhaled)

Suppress eosinophil activity.

✔ Biologics

Directly reduce eosinophils:

  • Mepolizumab (anti-IL-5)

  • Benralizumab (anti-IL-5 receptor)

  • Reslizumab (anti-IL-5 infusion)

Reduce eosinophil recruitment:

  • Dupilumab (anti-IL-4/IL-13)

  • Tezepelumab (broad upstream suppression)

These can transform life for patients with severe asthma or ABPA.

🧠 8. Summary

Eosinophils are key drivers of:

  • flare-ups

  • mucus plugging

  • wheeze

  • breathlessness

  • airway damage

Understanding them helps patients:

  • interpret blood tests

  • understand biologic treatments

  • recognise flare-up patterns

  • manage ABPA and asthma more confidently

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