PD-L1 (programmed death 1 ligand), also known as B7-H1, or CD274, is a member of the immune regulatory molecule B7 family and a transmembrane glycoprotein with a molecular weight of approximately 65kD. PD-L1 (programmeddeath-1 ligand), also known as B7-H1, or CD274, is a member of the immune regulatory molecule B7 family and a transmembrane glycoprotein with a molecular weight of approximately 65kD. Mature human PD-L1 consists of an extracellular domain of 220 amino acids (including 2 immunoglobulin like domains), a transmembrane domain of 21 amino acids, and a cytoplasmic domain of 31 amino acids. The interaction between PD-1 and PD-L1 can inhibit the proliferation of T cells and inhibit their production of IL-2 and INF- γ And IL-10. Recent studies have shown that the use of Anti PD-L1 mAb in vivo can regulate autoimmune diseases. Blocking the interaction between PD-1 and PD-L1 may provide feasible strategies for future therapeutic regulation of antiviral immunity, anti-tumor response, and autoimmune diseases.