Canine Interleukin-36 Receptor Antagonist (IL-36Ra) is an anti-inflammatory cytokine that regulates IL-36–mediated immune responses in dogs (Canis lupus familiaris). 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 activating it, thereby preventing proinflammatory cytokines such as IL-36α, IL-36β, and IL-36γ from initiating downstream signaling. Through this mechanism, canine IL-36Ra suppresses activation of intracellular pathways including NF-κB and MAPK, helping to limit production of inflammatory mediators and regulate immune responses at epithelial barrier tissues such as the skin and mucosal surfaces. In dogs, IL-36Ra contributes to maintaining immune homeostasis and controlling excessive inflammatory responses associated with infection, tissue injury, or allergic inflammation. In cell culture, recombinant canine IL-36Ra is commonly used to inhibit IL-36–induced inflammatory signaling in epithelial and immune cells, enabling investigation of cytokine regulation, epithelial–immune cell interactions, and inflammatory pathway modulation in vitro. Canine IL-36Ra is also relevant in translational veterinary research, particularly in studies of inflammatory skin diseases such as canine atopic dermatitis, where IL-36 pathway regulation is investigated to better understand inflammatory mechanisms and evaluate potential therapeutic strategies relevant to both canine and human dermatological conditions.