An ancient evolutionary origin for IL-1 cytokines.

Protein structure prediction identified a previously unrecognized IL-1 protein family, IL-1anc, with homologs throughout Eumetazoa, linking it to mammalian IL-1α/IL-1β features.

• Why it matters: The evolutionary origins of IL-1 cytokines are unclear because homologs outside vertebrates are hard to detect reliably with sequence-only methods.
• What they did: Using protein structure prediction, the authors searched for IL-1anc genes and then tested functionally relevant traits in Petromyzon marinus and Strongylocentrotus purpuratus, comparing expression, localization, and post-translational processing to mammalian IL-1α/IL-1β.
• The result: IL-1anc proteins in these model systems share key features with mammalian IL-1α/IL-1β, supporting an IL-1 superfamily module of animal immunity that predates jawed vertebrates.

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