PDCD1 and neoplasm: ▪Class of extracellular vesicles made and released by most cells; contains mRNA, miRNA and proteins.▪miRNAs in exosomes are more stable than serum miRNAs due to the double-membrane structure.▪Exosomes can bind to PD-1 on immune cells and thus actively suppress CD8+ lymphocytes. ▪Disadvantages:-Methods for tumor-derived exosome isolation and separation from human plasma-derived exosomes are not yet established and their role as biomarkers remains unconfirmed.-Low purity, specialized equipment required, exosome aggregation.