Cardiac endothelial cell-derived exosomes induce specific regulatory B cells

The mechanism of immune tolerance is to be further understood. The present study aims to investigate the role of the Cardiac endothelial cell (CEC)-derived exosomes in the induction of regulatory B cells. In this study, CECs were isolated from the mouse heart. Exosomes were purified from the culture supernatant of the primary endothelial cells. The suppressor functions of the regulatory B cells were determined by flow cytometry. The results showed that the CEC-derived exosomes carried Integrin αvβ6. Exposure to lipopolysaccharide (LPS) induced B cells to express the latent transforming growth factor (TGF)-β, the latter was converted to the active form, TGF-β, by the exosome-derived αvβ6. The B cells released TGF-β in response to re-exposure to the exosomes in the culture, which suppressed the effector T cell proliferation. We conclude that CEC-derived exosomes have the capacity to induce B cells with immune suppressor functions.