Suppression of acute and protracted-relapsing experimental allergic encephalomyelitis by nasal administration of low-dose IL-10 in rats

In this study we report for the first time that nasal administration of the Th2 cell-related cytokine interleukin-10 (IL-10), at concentrations of 1.5 μg/rat and 15 μg/rat, suppressed clinical signs of acute experimental allergic encephalomyelitis (EAE) in Lewis rats and prevented the development and relapse of protracted-relapsing EAE (PR-EAE) in DA rats. In contrast, subcutaneous injection of IL-10 (15 μg/rat) did not inhibit acute EAE. The IL-10-mediated suppression of EAE was associated with decreased myelin antigen-specific T-cell proliferative responses and IFN-γ secretion in both acute and PR-EAE. In sections of spinal cords derived from rats nasally pretreated with IL-10, there were no infiltrating CD4 + T cells or macrophages, which are considered major encephalitogenic or inflammatory cells. Most interestingly, nasally administered IL-10 also inhibited MHC class II expression in microglia, indicating that IL-10 administration by the nasal route prevents the activation of microglia. Administration of cytokines via the nasal route offers an exciting alternative in the prevention and treatment of autoimmune diseases.