AbstractBackgroundMultiple sclerosis (MS) is an autoimmune disorder characterized by chronic inflammation, demyelination, and neuronal damage. During autoimmunity, cytokines are important mediators of the inflammation. In this line, interleukin-27 (IL-27) modulates inflammation and can be produced directly at inflammatory sites such as in the joints during rheumatoid arthritis or in the central nervous system (CNS) during MS. While in animal models of MS, treatment with IL-27 decreases the disease severity, its role in humans is not clearly established and it is not known if IL-27 could be detected in the cerebrospinal fluid (CSF) of MS patients.MethodsIn this study, we measured IL-27 levels using a quantitative enzyme-linked immunosorbent assay in CSF of patients with relapsing remitting multiple sclerosis (RRMS), isolated optic neuritis (ON) and non-inflammatory neurological disease (NIND) as well as in the sera of healthy donors (HD) and RRMS patients undergoing different disease modifying treatments. We further confirmed by immunohistology of patient biopsies the identity of IL-27 producing cells in the brain of active MS lesions.ResultsWe observed that IL-27 levels are increased in the CSF but not in the sera of RRMS compared to HD. We confirmed that IL-27 is expressed in active MS plaques by astrocytes of MS patients.ConclusionsOur results point toward a local secretion of IL-27 in the CNS that is increased during autoimmune processes. We propose that local production of IL-27 could sign the induction of a regulatory response that promotes inflammation’s resolution. The effect of new immunomodulatory therapies on cerebral IL-27 production could be used to understand the biology of IL-27 in MS disease.