Interferon-β (IFN-β) is a mainstay therapy for multiple sclerosis. However, only two thirds of patients respond to therapy, and clinical symptoms worsen in some patients. Chandar Raman and his colleagues show that IFN-β alleviates disease induced by T helper type 1 cells and exacerbates disease induced by T helper type 17 cells in mice. They also show that these effects of IFN-β rely on IFN-γ signaling ( pages 376–377 ). Interferon-β (IFN-β) is the major treatment for multiple sclerosis. However, this treatment is not always effective. Here we have found congruence in outcome between responses to IFN-β in experimental autoimmune encephalomyelitis (EAE) and relapsing-remitting multiple sclerosis (RRMS). IFN-β was effective in reducing EAE symptoms induced by T helper type 1 (TH1) cells but exacerbated disease induced by TH17 cells. Effective treatment in TH1-induced EAE correlated with increased interleukin-10 (IL-10) production by splenocytes. In TH17-induced disease, the amount of IL-10 was unaltered by treatment, although, unexpectedly, IFN-β treatment still reduced IL-17 production without benefit. Both inhibition of IL-17 and induction of IL-10 depended on IFN-γ. In the absence of IFN-γ signaling, IFN-β therapy was ineffective in EAE. In RRMS patients, IFN-β nonresponders had higher IL-17F concentrations in serum compared to responders. Nonresponders had worse disease with more steroid usage and more relapses than did responders. Hence, IFN-β is proinflammatory in TH17-induced EAE. Moreover, a high IL-17F concentration in the serum of people with RRMS is associated with nonresponsiveness to therapy with IFN-β.

T helper type 1 and 17 cells determine efficacy of interferon-β in multiple sclerosis and experimental encephalomyelitis