Rabbit Programmed Death-Ligand 1 (PD-L1) (CD274, also known as B7-H1) is an immune checkpoint protein that regulates T cell activation and immune tolerance in rabbits (Oryctolagus cuniculus). PD-L1 is a member of the B7 family of immunoregulatory proteins, which includes PD-L2 (CD273), CD80 (B7-1), CD86 (B7-2), ICOS-L (B7-H2), and B7-H3, molecules that control costimulatory and coinhibitory signaling during immune responses. PD-L1 is expressed on antigen-presenting cells such as macrophages and dendritic cells, as well as epithelial cells, endothelial cells, and some tumor or infected cells, and interacts with its receptor PD-1 (Programmed Death-1, CD279) on activated T lymphocytes. Binding of PD-L1 to PD-1 transmits inhibitory signals that reduce T cell proliferation, cytokine production, and cytotoxic activity, helping maintain immune homeostasis and preventing excessive inflammatory responses. In rabbits, PD-L1-mediated signaling is relevant in immune regulation during infection, inflammation, and tumor development, where increased PD-L1 expression may contribute to T cell suppression and immune evasion. Because rabbits are used as experimental models for infectious disease, immunology, and cancer research, characterization of rabbit PD-L1 supports studies of immune checkpoint regulation, host–pathogen interactions, and evaluation of immunomodulatory therapies, providing insight into mechanisms of immune tolerance and immune evasion relevant to human disease.