IL-1 family cytokines in inflammation and immunity

Interleukin-1 (IL-1) was the first interleukin identified as a potent proinflammatory and multifunctional molecule involved in innate immune responses against microbes, as well as in conditions of tissue injury associated with infections and sterile conditions. IL-1 is part of a large system, the IL-1 system, comprising a family of ligands that act as agonists, receptor antagonists, and anti-inflammatory cytokines, as well as a family of receptors that includes signaling receptor complexes, decoy receptors and negative regulators. All the members of the IL-1 system are involved in inflammatory diseases, innate and adaptive immune responses, conditions associated with dysmetabolism, and cancer by affecting both the tumor microenvironment and cancer cells. The deregulated or excessive activation of several pathways associated with the IL-1 system may lead to detrimental inflammatory or immune reactions, including autoinflammatory, autoimmune, infectious and degenerative diseases. The negative regulation of the IL-1 system mediated by antagonists, decoy receptors, scavengers, and dominant-negative molecules plays nonredundant roles in controlling these conditions. Owing to the central role of IL-1 in the pathogenesis of inflammation-driven diseases, IL-1 blocking agents are approved for clinical use in several inflammatory conditions, and inhibitory agents for other members of the family are under development. Here, the complexity of the IL-1 system, the involvement of its different members in inflammation-driven diseases, and the therapeutic approaches to target members of pathways associated with these conditions are presented and discussed.