Immunology · Cytokines and molecules
Interleukin-1 !
- Molecule
IL-1 is an alarm cytokine made by macrophages: it causes fever and inflammation, and its excess drives rare inherited fever syndromes.
Updated 2026-11-01
What it is
Interleukin-1 is a family of cytokines; the two classic members are IL-1α and IL-1β, which share one signalling receptor (IL-1R1). IL-1β is made as an inactive precursor that must be cut by caspase-1, activated inside a protein complex called the inflammasome (NLRP3 is the best known). It is a central driver of fever and acute inflammation, and blocking it controls autoinflammatory diseases.
Structure
- IL-1α: often stays inside or on the cell and acts as an alarm signal released by damaged cells.
- IL-1β: secreted after caspase-1 cleaves its precursor (pro-IL-1β).
- Receptor: IL-1R1, which signals through MyD88, IRAK and TRAF6 to switch on NF-κB.
Function
- Raises the hypothalamic set point (fever).
- Activates endothelium so leukocytes can stick and leave the vessel.
- Induces other cytokines (IL-6, chemokines such as IL-8) and matrix-degrading enzymes.
- Contributes to systemic inflammation in sepsis.
Clinical notes
- Cryopyrin-associated periodic syndromes (gain of function of NLRP3): fever, urticaria-like rash, joint pain; treated with IL-1 blockers.
- Familial Mediterranean fever: IL-1 blockade is an option when colchicine fails or is not tolerated.
- Gout: urate crystals activate the inflammasome; canakinumab is approved for difficult flares.
- Still disease and systemic juvenile idiopathic arthritis: IL-1 blockers are used; macrophage activation syndrome is a feared complication.
- IL-1 blockers raise the risk of infections; latent tuberculosis is screened for before canakinumab.
Test yourself
Think of the answer, then tap the question to see it.
Which enzyme converts pro-IL-1β to its active form?
Caspase-1, activated inside the inflammasome (for example NLRP3).
What is anakinra?
A recombinant form of the natural IL-1 receptor antagonist; it competes with IL-1α and IL-1β for IL-1R1.
Which group of diseases shows the best response to IL-1 blockade?
Autoinflammatory diseases such as cryopyrin-associated periodic syndromes, FMF, TRAPS and mevalonate kinase deficiency.
Related
- Cytokines: the table to know
- Interleukin-6
- TNF-α
- IL-8 and the chemokines
- Acute-phase response and fever (CRP, ESR, procalcitonin)
- Acute inflammation: vascular and cellular events
- Monocyte and macrophage
- Pattern recognition: PAMPs, DAMPs, Toll-like receptors
Related conditions
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: Targeting IL-1β in the Treatment of Atherosclerosis (Frontiers in Immunology, 2020); Pro-Inflammatory and Anti-Inflammatory Interleukins in Infectious Diseases: A Comprehensive Review (Tropical Medicine and Infectious Disease (PubMed Central), 2024); Canakinumab Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); Rilonacept Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025).
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Representative model, for educational purposes only.