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Description

Programmed cell death 1 ligand 1 (UniProt Q9NZQ7, also known as B7-H1, B7 homolog 1, CD274, PD-L1, PDCD1 ligand 1, Programmed death ligand 1) is encoded by the CD274 (also known as B7H1, PDCD1L1, PDCD1LG1, PDL1) gene (Gene ID 29126) in human. PD-L1 is a single-pass type I membrane protein that plays a critical role in induction and maintenance of immune tolerance to self. It is expressed on activated T- and B-cells, dendritic cells, keratinocytes, and monocytes. Higher expression has also been reported in heart, skeletal muscle, placenta, and lung. PD-1 and PD-1 ligands 1 and 2 (PD-L1 and PD-L2) are B7:CD28 family members that regulate T cell activation and peripheral tolerance. When engaged together with the TCR, the interaction of PD-1 with its ligands delivers an inhibitory signal to T cell proliferation and cytokine production. While PD-L1 is broadly expressed in hematopoietic and nonhematopoietic cells, PD-L2 expression is highly restricted to antigen presenting cells (APCs), including dendritic cells (DCs) and macrophages. The PD-1 pathway plays a key role in the progressive loss of effector T cell responses during chronic HIV infection. Under some conditions, blockade of this pathway can restore many T cell functions. PD-L1 is initially produced with signal peptide (aa 1-18) sequence, which is subsequently cleaved off to produce the mature protein with a large extracellular (aa 19-238) region that contains an Ig-like V-type domain (aa 19-127) and an Ig-like C2-type domain (aa 133-225), followed by a transmembrane domain (aa 239-259) and a cytoplasmic tail (aa 260-290).