Small Extracellular Vesicle PD-L1 in Cancer: The Knowns and Unknowns

The authors summarize and discuss the latest research and advancements on small extracellular vesicle (sEV) programmed death protein 1 ligand (PD-L1), including the biogenesis and secretion mechanisms, isolation and detection strategies, as well as the biological functions of sEV PD-L1.