Programmed cell death 1 ligand 2 (also known as PD-L2, B7-DC) in humans is a protein encoded by the PDCD1LG2 gene. The gene is located on chromosome 9, p24.2. PD-L2 is one of two programmed death ligands (PD-1) and is a member of the CD28 family of immunoreceptors. Widely expressed PD-L2 was detected by Northern blot analysis and was highest in the placenta, heart, pancreas, lungs, and liver, and lower in the spleen, lymph nodes, and thymus.PD-L2 counter-regulates T cells and has an important role in immune tolerance. At sites of inflammation, PD-L2 upregulated synoviocytes, infiltrating macrophages, dendritic cells, and airway epithelial cells. Furthermore, in macrophages and alveolar epithelial cells PD-L2 binds RGM-B thus supporting respiratory immune tolerance.