PDCD1LG (PDL2, CD273, programmed cell death 1 ligand 2) is a ligand for the programmed death-1 receptor (PD1), which is part of the inhibitory T-cell response (immune checkpoint) pathway and a molecule involved in peripheral tolerance and immune escape mechanisms during chronic viral infections and cancer. PDL2 functions in the induction and effector phases of T-cell immunity, dampening and regulating T-cell responsiveness, and inhibiting T cell proliferation, cytokine production, and cell adhesions. It is expressed in a variety of tissues and cancers, and along with PD1, a target of immunotherapy designed to block inhibitory receptors that are upregulated on tumor-associated T cells (immune checkpoint blockade). References: Clin Dev Immunol 2012 ID656340; Int immunol 2010 22(*):651; Clin Can Res 2017 23(12):3158.