EBV + B cell-derived exosomes promote EBV-associated T/NK-cell lymphoproliferative disease immune evasion by STAT3/IL-10/PD-L1 pathway.

Abstract

EBV-associated T/NK-cell lymphoproliferative diseases (EBV-T/NK-LPDs) are characterized by the clonal proliferation of EBV-positive ( +) T/NK cells. EBV is typically latent in B cells and the mechanism by which the EBV genome invades T/NK cells remains unknown. Recent studies have demonstrated that exosomes derived from EBV + B cells play a pivotal role in immunosuppressive microenvironment remodeling. Moreover, the existence of an immunosuppressive microenvironment is known to be critical in the development of EBV-T/NK-LPDs. Hence, we hypothesized that exosomes derived from EBV + B cells might promote the development of EBV-T/NK-LPDs by stimulating immune evasion. In this study, we utilized paraffin sections to clarify the STAT3/IL-10/PD-L1-associated immunosuppressive microenvironment in EBV-T/NK-LPDs. Further, we extracted exosomes from BL2009 (EBV + B cell lymphoma) and CA46 (EBV- B cell lymphoma) cell lines to co-culture with cutaneous T-cell lymphoma (CTCL) cell lines, to verify the changes in the above immune evasion pathway. The paraffin sections of EBV-T/NK-LPDs showed high-expression levels of IL-10/PD-L1, which might be related to the phosphorylation of STAT3. Exosomes derived from EBV + B cells could significantly activate the STAT3/IL-10/PD-L1 pathway. After being treated with C188-9, EBV + B cell-derived exosomes were no longer able to stimulate the expression of IL-10/PD-L1 in CTCL cells. EBV-T/NK-LPDs have a STAT3/IL-10/PD-L1 overactivation-associated immunosuppressive microenvironment. Our study elucidated part of this mechanism. Exosomes derived from EBV + B could induce phosphorylation of STAT3 in CTCL cells, leading to the overexpression of IL-10/PD-L1. Our findings might shed light on new directions for understanding immune evasion in EBV-T/NK-LPDs.