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Immunology · Cytokines and molecules

IL-4, IL-5 and IL-13 (the Th2 cytokines) !

  • Molecule

IL-4, IL-5 and IL-13 run allergic (type 2) inflammation: IgE, eosinophils and mucus. They are targets of modern asthma and eczema biologics.

Updated 2026-11-01

What it is

IL-4, IL-5 and IL-13 are the signature cytokines of type 2 immunity, made by Th2 cells and by group 2 innate lymphoid cells (ILC2). Epithelial alarm signals (TSLP, IL-33, IL-25) start the response after allergen contact. Together they produce IgE, recruit and sustain eosinophils and remodel the airway, which defines type 2-high asthma and atopic disease.

Function

  • Defence against helminths (worms) is the physiological role of type 2 immunity.
  • IL-4 inhibits Th1 responses, and IFN-γ inhibits Th2: the two arms balance each other.
  • IL-4 induces adhesion molecules (VCAM-1) that help eosinophils leave the blood.

Step by step

  1. Allergen contacts the airway epithelium, which releases TSLP, IL-33 and IL-25.
  2. Dendritic cells and ILC2 respond; naive CD4 T cells become Th2 cells under IL-4.
  3. IL-4 (with IL-13) switches allergen-specific B cells to IgE; IgE binds FcεRI on mast cells.
  4. IL-5 expands eosinophils, which enter the airway wall and release granule proteins.
  5. IL-13 causes mucus, smooth-muscle hyperreactivity and fibrosis: chronic asthma.

Clinical notes

  • Allergic and eosinophilic asthma, allergic rhinitis, chronic rhinosinusitis with nasal polyps.
  • Atopic dermatitis: dupilumab and IL-13 blockers (tralokinumab, lebrikizumab).
  • Eosinophilic esophagitis and hypereosinophilic syndromes (dupilumab, mepolizumab, depending on the condition).
  • Biologics do not treat an acute asthma attack; they reduce exacerbations and oral steroid needs.

In the lab

  • Blood eosinophil count and total serum IgE.
  • Fractional exhaled nitric oxide (FeNO) as a marker of IL-13 activity in the airway.

Test yourself

Think of the answer, then tap the question to see it.

Which cytokine is essential for eosinophil development and survival?

IL-5; mepolizumab blocks IL-5 and benralizumab blocks its receptor.

Why does dupilumab block both IL-4 and IL-13?

It binds the IL-4 receptor α chain, which is part of the receptors used by both cytokines.

Which three markers point to type 2-high asthma?

Raised blood eosinophils, raised fractional exhaled nitric oxide and raised total IgE.

What is the normal (non-allergic) role of type 2 immunity?

Defence against helminths and tissue repair; allergy is the same response aimed at harmless antigens.

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← All of immunology

Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given.

Sources: T-helper cells and their cytokines in pathogenesis and treatment of asthma (Frontiers in Immunology, 2023); Immunologic aspects of asthma: from molecular mechanisms to disease pathophysiology and clinical translation (Frontiers in Immunology, 2024); Tralokinumab-ldrm injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); Pro-Inflammatory and Anti-Inflammatory Interleukins in Infectious Diseases: A Comprehensive Review (Tropical Medicine and Infectious Disease (PubMed Central), 2024).

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Representative model, for educational purposes only.