Immunomodulatory function of Treg-derived exosomes is impaired in patients with relapsing-remitting multiple sclerosis.

Multiple sclerosis (MS) is an autoimmune disease which is characterized by neuroaxonal degeneration in the central nervous system. Impaired function of regulatory T cells (Tregs) is believed to be an underlying pathogenic mechanism in MS. Tregs is able to release exosomes, which contain a considerable amount of protein and RNA. Exosomes are capable of transporting their content to other cells where the released content exerts biological functions. Here, we investigated whether Tregs exosomes of RRMS patients or healthy controls might regulate the proliferation or survival of T lymphocytes. Regulatory T cells derived from MS patients or healthy controls were cultured for 3 days and exosomes were purified from supernatants. Treg-derived exosomes were co-cultured with conventional T cells (Tconv). The percentages of Tconv proliferation and apoptosis were measured. Our findings showed that the percentage of proliferation suppression induced by exosomes in patients compared to healthy controls was 8.04 ± 1.17 and 12.5 ± 1.22, respectively, p value = 0.035. Moreover, the rate of Tconv apoptosis induced by exosome of MS patient was less than healthy controls (0.68 ± 0.12 vs. 1.29 ± 0.13; p value = 0.015). Overall, Treg-derived exosomes from MS patients and healthy controls suppressed the proliferation and induced apoptosis in Tconv. However, the effect of MS-derived exosomes was significantly less than healthy controls. Our results point to an alternative Treg inhibitory mechanism which might be important in immunopathogenesis of MS. Although, the cause of the exosomal defect in MS patients is unclear, manipulation of patients' Treg-derived exosomes to restore their suppressive activity might be considered as a potential therapeutic approach. Graphical abstract ᅟ.