BackgroundExcessive proliferation and activation of B cells, resulting in the production of various autoantibodies, is a crucial link and significant feature of the pathogenesis of systemic lupus erythematosus (SLE), as well as the pathological basis of systemic multiorgan damage. However, whether exosomes derived from human umbilical cord mesenchymal stem cells (hucMSCs-Exo) are involved in the immune regulation of SLE has not been clarified.ObjectivesTherefore, our study aimed to investigate the efficacy of hucMSCs-Exo for treating SLE.MethodshucMSCs-Exo and peripheral blood mononuclear cells (PBMCs) of SLE patients were coculturedin vitro, and B cell apoptosis, activation, proliferation, and inflammation levels were detected by flow cytometry. Subsequently, the expression level of miR-155 in B lymphocytes of SLE patients was detected by qRT-PCR, and the target gene relationship between miR-155 and SHIP-1 was found through bioinformatics and dual luciferase activity experiments, which verified the inhibition of miR-155 in B lymphocytes of SLE patients to regulate immunity.ResultsWe found that hucMSCs-Exo promoted B cell apoptosis, prevented B cell overactivation, and reduced inflammation. MicroRNA-155 (miR-155) has a powerful regulatory function in B cells. It was demonstrated that hucMSCs-Exo acts synergistically with miR-155 inhibitors to target SHIP-1 to B cells more effectively than exosomes alone.ConclusionOur results provide insight into how hucMSCs-Exo regulates autoimmunity in patients with lupus and suggest targeting miR-155 for autoimmunity while protecting immunity.