Immunology · Cytokines and molecules
Interleukin-17 !
- Molecule
IL-17 calls neutrophils to skin and mucosa and protects against Candida; too much of it drives psoriasis.
Updated 2026-11-01
See it in 3D: Skin
What it is
IL-17 is a family of six cytokines; IL-17A and IL-17F are the most important in disease. They are made by Th17 cells and also by γδ T cells, MAIT cells and group 3 innate lymphoid cells. IL-17 acts on epithelial cells and keratinocytes, which then release chemokines (IL-8, CCL20) and antimicrobial peptides, bringing neutrophils and more Th17 cells to the site.
Function
- Defence of skin and mucosa against fungi (especially Candida) and extracellular bacteria.
- Induces keratinocytes to make chemokines and antimicrobial peptides.
- Its receptor is a heterodimer that includes IL-17RA and is widely expressed on epithelial cells.
Clinical notes
- Psoriasis: the IL-23/IL-17 axis is the central driver of plaques; IL-17A blockade acts quickly.
- Axial spondyloarthritis and psoriatic arthritis respond to IL-17 blockade; hidradenitis suppurativa is another approved use of secukinumab.
- Unlike anti-TNF and anti-IL-12/23 drugs, anti-IL-17 agents did not help Crohn disease and some patients worsened, suggesting IL-17 protects the gut lining.
- Before treatment latent tuberculosis is screened for, as with other biologics.
Test yourself
Think of the answer, then tap the question to see it.
Which infection points to a defect in IL-17 immunity?
Chronic mucocutaneous candidiasis, recurrent Candida of skin, nails and mucosa.
Why are IL-17 blockers avoided in active Crohn disease?
Trials showed no benefit and some flares; IL-17 seems to help protect the intestinal barrier.
What do keratinocytes release under IL-17 stimulation?
Chemokines such as IL-8 and CCL20 and antimicrobial peptides such as β-defensin 2, which bring in neutrophils and Th17 cells.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Cytokines: the table to know
- IL-12 and IL-23
- IL-8 and the chemokines
- Interleukin-6
- IL-10 and TGF-β (the brakes)
- Th1, Th2, Th17, Tfh and Treg
- Neutrophil
- T-cell and combined deficiencies: DiGeorge, SCID, Wiskott–Aldrich, ataxia-telangiectasia
Related conditions
Microorganisms
In Pharmacology
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: Major Role of the IL17/23 Axis in Psoriasis Supports the Development of New Targeted Therapies (Frontiers in Immunology, 2021); Secukinumab 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); Th17/Treg imbalance in inflammatory bowel disease: immunological mechanisms and microbiota-driven regulation (Frontiers in Immunology, 2025).
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Representative model, for educational purposes only.