PDCD1LG2 and neoplasm: PD-1 receptor is an immune check point, which plays a crucial role in tumour microenvironment.17 PD-L1 (B7-H1) is a main ligand for PD-1 and PD-L2 (B7-DC) is another ligand for PD-1.17 As previously noted, targeting PD-1 and PD-L1 has shown dramatic response in many types of tumour.