Tumor-derived small extracellular vesicle PD-L1 impedes macrophage-mediated antibacterial immunity in preexisting malignancy

Tumor-derived small extracellular vesicles (TEVs) were reported to carry various immunosuppressive molecules regulating immune response. We previously reported that TEV could express PD-L1 to systematically inhibit CD8 T cell anti-tumor immunity. Here, we observed that TEV PD-L1 suppressed the phagocytosis and bactericidal capacity of macrophages against E. coli. To investigate the potential mechanisms behind the impaired phagocytosis further, we collected and purified exosomes from the melanoma cell line B16-F10 PD-L1 knockout (KO) or vector culture to challenge RAW264.7 cells. We used RNA sequencing to reveal the key functional associated molecules for inhibiting the phagocytosis-associated pathway. Comparative gene expression profiling analysis of RNA-sequencing (RNA-seq) data for B16 PD-L1 KO and its control exosomes treated LPS induced RAW264.7 cells.