Programmed cell death 1 ligand 2 (PD-L2) is a protein that is encoded by the PDCD1LG2 gene in humans. PDCD1LG2 has also been designated as CD273 (cluster of differentiation 273). Inhibitory molecules of the B7/CD28 family play a key role in the induction of immune tolerance in the tumor microenvironment. The programmed death-1 receptor (PD-1), with its ligands PD-L1 and PD-L2, constitutes an important member of these inhibitory pathways. PD-L2 expression was initially thought to be restricted to antigen-presenting cells such as macrophages and dendritic cells (DCs). However, PD-L2 expression can be induced on a wide variety of other immune cells and nonimmune cells depending on micro environmental stimuli.