The biological master switch that can trigger or tame systemic inflammation

Science · Published 24 October 2026 Swipe more like this →

In short: First identified in the 1980s, Interleukin-1 is a potent molecular messenger. It can orchestrate massive immune responses to microbes or drive devastating autoinflammatory diseases. Understanding how the body balances these powerful signals is the key to modern therapies for chronic inflammation.

Interleukin-1 (IL-1) is a multifunctional molecule central to the innate immune response. As one of the first interleukencies identified, it acts as a potent proinflammatory driver in response to tissue injury, microbes, or danger signals like uric acid crystals. The IL-1 system is a complex network of 11 proteins encoded by distinct genes, including seven agonists like IL-1α, IL-1β, and IL-18, alongside anti-inflammatory regulators like IL-37. This expansive family also includes three specific receptor antagonists: IL-1Ra, IL-36Ra, and IL-38. Beyond just microbes, these cytokines respond to sterile conditions and various forms of tissue damage.

The mechanism of action relies on a sophisticated signaling cascade. When ligands bind to receptors, they activate the intracellular TIR domain. This process initiates the MyD88 adapter protein, which promotes NF-κB movement into the nucleus and triggers mitogen-activated protein kinases (MAPKs) including ERK, JNK, and p38. This process amplifies inflammation by inducing the expression of hundreds of genes, including IL-6 and COX-2. This signaling pathway is shared with Toll-like receptors, which also utilize the TIR domain for communication. The cascade relies on a complex sequence of phosphorylation and ubiquitine events to function.

Because excessive activation can lead to autoimmune and degenerative diseases, the body employs a 'decoy' and antagonist strategy to maintain balance. For instance, the IL-1R2 receptor acts as a decoy, while antagonists like IL-1Ra compete for receptor binding. The clinical importance of this regulation is profound: blocking IL-1α or IL-1β with recombinant IL-1RA or antibodies has successfully treated various autoinflammatory conditions, proving that controlling this single pathway can stabilize systemic immune dysfunction. The system is highly regulated through negative regulators like SIGIRR and various scavenger molecules. This precise control is vital, as mutations in the IL-1RA gene can lead to severe multiorgan inflammation.

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