Rabbit TNFSF15 (Tumor Necrosis Factor Superfamily Member 15, also known as TL1A or VEGI—vascular endothelial growth inhibitor) is a cytokine belonging to the tumor necrosis factor (TNF) superfamily, which includes related ligands such as TNF-α, Fas ligand (FasL), CD40 ligand (CD40L), TRAIL, and RANKL that regulate immune signaling, apoptosis, and inflammatory responses. In rabbits (Oryctolagus cuniculus), TNFSF15 is primarily produced by endothelial cells, macrophages, dendritic cells, and other immune cells in response to infection, inflammation, or tissue injury. TNFSF15 functions mainly by binding to death receptor 3 (DR3, TNFRSF25) expressed on T lymphocytes and other immune cells, activating intracellular signaling pathways such as NF-κB and MAPK that regulate T cell activation, cytokine production, and inflammatory responses. In rabbits, TNFSF15 is also associated with regulation of vascular endothelial cell proliferation and angiogenesis, reflecting its alternative designation as VEGI. Because rabbits are widely used as experimental models for immunology, inflammatory disease, and cardiovascular research, characterization of rabbit TNFSF15 supports studies of cytokine-mediated immune regulation, inflammatory signaling pathways, and vascular biology, providing insights relevant to both veterinary and human biomedical research.