Rabbit Interleukin-1 Receptor Antagonist (IL-1Ra) is an anti-inflammatory cytokine produced by monocytes, macrophages, neutrophils, and other immune and stromal cells in rabbits (Oryctolagus cuniculus) that functions as a key regulator of IL-1–mediated inflammation. IL-1Ra competitively binds to the IL-1 receptor type 1 (IL-1R1) without triggering intracellular signaling, thereby inhibiting the pro-inflammatory actions of IL-1α and IL-1β and limiting activation of NF-κB and MAPK pathways that drive fever, leukocyte recruitment, and tissue inflammation. In rabbit health, IL-1Ra plays an important role in modulating inflammatory responses associated with respiratory infections such as Pasteurella multocida, viral diseases including rabbit hemorrhagic disease virus (RHDV) and myxoma virus, and inflammatory conditions affecting joints and vasculature. Rabbits are widely used as models for atherosclerosis, osteoarthritis, and inflammatory eye disease, where IL-1 signaling contributes to tissue pathology and IL-1Ra helps regulate disease progression. As both a biomarker and a functional inhibitor of IL-1 activity, rabbit IL-1Ra is important in studies of inflammasome regulation, cytokine balance, and evaluation of anti-inflammatory therapies, supporting translational research relevant to human inflammatory and autoimmune disorders.