CD80⁺ dendritic cell derived exosomes inhibit CD8⁺ T cells through down-regulating NLRP3 expression after liver transplantation

Background: Graft-infiltrated dendritic cells (DCs) and CD8⁺ T lymphocytes are closely related with immune regulation after liver transplantation (LT). An additional factor which appears to play an important role with regard to transplantation immunity are exosomes, which are membrane-derived small vesicles released by various cells. However, the regulation of CD80⁺ DCs derived exosomes on CD8⁺ T cells in response to LT remains unclear.

Methods: Ten LT patients and two donors were included in this study. Multiple immunofluorescencewas performed to identify infiltratedCD8⁺ Tcells and DCs in human liver samples. The expression of NLRP3 and Ki-67 were measured usingimmunohistochemistry and immunofluorescence staining.Changes in CD80⁺ DCs and CD8⁺ T cells within the liver and blood of a mouse model of LT were detected with flow cytometry. After coculture with CD80⁺ DCs derived exosomes, the proliferation, adhesion, and transmigration ofCD8⁺ T cells were determined with the use of CCK-8, Adhesion and Transmigration assay in vitro.CD8⁺ T cells related cytokines were measured using Western blot, qRT-PCR and ELISA.

Results: In human liver samples, there was an increase in intrahepatic CD8⁺ T cell infiltration in the acute LT rejection group, an effect which was accompanied by high expressions of NLRP3 and Ki-67 index and a decrease in DCs. Similarly, lower levels of CD80⁺ DCs were observed with acute rejection in an LT mouse model, along with increased numbers of CD8⁺ T cells in the liver and blood. In vitro, CD80⁺ DCs derived exosomes modulated the secretion of CD8⁺ T cells from cytokines by down-regulating NLRP3 expression, combined with a synchronous inhibition in the adhesion, invasion, and proliferation of CD8⁺ T cells.

Conclusion: CD80⁺ DCs derived exosomes negatively regulate CD8⁺ T cells via inhibition of NLRP3 expression, a series of events which are essential to attenuate acute LT rejection. These results reveal a new role for CD80⁺ DCs exosomes as related to tolerance induction in LT.