Provided are antibodies that specifically bind to Programmed Death-1 (PD1, Pdcd-1, or CD279) ligand (PD-L1) and inhibit PD-L1-mediated cellular signaling and activities in immune cells, antibodies binding to a set of amino acid residues required for its ligand binding, and uses of these antibodies to treat or diagnose cancer, infectious diseases or other pathological disorders modulated by PD-L1-mediated functions.本發明提供特異性結合至計畫性死亡-1（PD1、Pdcd-1或CD279）配體(PD-L1)並抑制免疫細胞中PD-L1介導的細胞傳訊及活性的抗體，結合至配體結合所需要之一組胺基酸殘基的抗體，及該等抗體治療或診斷由PD-L1介導功能所調變的癌症、傳染性疾病或其他病理學病症之用途。
