Feline Interleukin-36 Receptor Antagonist (IL-36Ra) is an anti-inflammatory cytokine that regulates IL-36–mediated immune responses in cats (Felis catus). IL-36Ra is a member of the IL-1 cytokine family and functions as a natural inhibitor of the IL-36 signaling pathway by binding to the IL-36 receptor (IL-36R, also known as IL1RL2) without inducing receptor activation, thereby preventing proinflammatory cytokines such as IL-36α, IL-36β, and IL-36γ from initiating downstream signaling. Through this mechanism, feline IL-36Ra suppresses activation of intracellular pathways including NF-κB and MAPK, helping to limit inflammatory mediator production and regulate immune responses at epithelial barrier tissues such as the skin and mucosal surfaces. In cats, IL-36Ra contributes to maintaining immune homeostasis and controlling excessive inflammatory responses. In cell culture, recombinant feline IL-36Ra is commonly used to inhibit IL-36–induced signaling in epithelial and immune cells, allowing researchers to study regulation of inflammatory pathways, cytokine production, and epithelial–immune cell interactions in vitro. Feline IL-36Ra is also relevant in translational medicine research because dysregulation of IL-36 signaling is associated with inflammatory skin diseases in humans, including generalized pustular psoriasis; feline and other animal models help researchers investigate IL-36 pathway regulation and evaluate potential anti-inflammatory therapeutic strategies targeting IL-36 signaling.