PDCD1 and neoplasm: We showed that the presence of sEV at high levels correlated with increased frequencies of CD8+PD-1+ and CD8+PD-L1+T-cells in treatment-naïve patients, suggesting a possible mechanism by which sEV suppress immune stimulation via the PD-L1/PD-1 pathway, eventually leading to the impairment of anti-tumor immune responses.