IL-37 suppresses CNS autoimmunity by increasing the frequency of Treg cells and reducing CD4 + T cell-derived IL-10 production.

Background: Interleukin-37 (IL-37) has anti-inflammatory properties in innate and adaptive immunity. Patients with multiple sclerosis (MS), an autoimmune inflammatory demyelinating disease of the central nervous system (CNS), have increased serum levels of IL-37. However, it is unknown whether IL-37 has an inhibitory effect on ongoing autoimmune neuroinflammation, thus offering a potential MS therapy.

Aim: Here, we examined the effect of IL-37 in an experimental autoimmune encephalomyelitis (EAE) model after disease onset to determine if it was protective.

Findings: IL-37-treated mice developed a less severe disease than control mice, with reduced demyelination as determined by increased expression of myelin basic protein. IL-37 suppressed inflammation by decreasing infiltration of CD4 + T cells into the CNS and increasing the frequency of regulatory T cells, while IL-10 expression by CD4 + T cells decreased over time in the CNS.

Conclusion: Our findings confirm the immunomodulatory role of IL-37 in CNS inflammation during ongoing disease, thus indicating the potential of IL-37 as an inhibitory reagent for MS therapy.