A ligand that binds to but fails to activate the INTERLEUKIN 1 RECEPTOR. It plays an inhibitory role in the regulation of INFLAMMATION and FEVER. Several isoforms of the protein exist due to multiple ALTERNATIVE SPLICING of its mRNA.

A synthetic form of native human IL-1Ra that has an additional methionine residue at its amino terminus.

Synonyms: Interleukin 1 Inhibitor, Urine, Antril, IL-1Ra, IL1 Inhibitor, Urine-Derived, Urine IL-1 Inhibitor, IL1 Febrile Inhibitor, IL-1 Inhibitor, Urine, 0, Kineret, Urine Derived IL1 Inhibitor, Febrile Inhibitor, IL1, Interleukin 1 Receptor Antagonist Protein, IL 1 Inhibitor, Urine, Urine-Derived IL1 Inhibitor, 9013DUQ28K, Anakinra