IFNb has been used as a first line therapy for relapsing remitting multiple sclerosis (RRMS). Since only a few studies have addressed the role of endogenous IFNb in the pathogenesis of the disease, our objective was to characterize its role in the transcriptional regulation of pathogenic Th17 cytokines in patients with RRMS. In-vitro studies have demonstrated that IFNb inhibited IL-17A, IL-17F, IL-21, IL-22 and IFN-b secretion in CD4+ lymphocytes through the induction of suppressor of cytokine secretion (SOCS)1 and 3. We found that patients with RRMS have increased serum and cerebrospinal fluid (CSF) Th17 (IL-17A and IL-17F) cytokine levels in comparison to the control subjects, suggesting that deficient endogenous IFNbeta secretion and/or signaling may contribute to the dysregulation of those pathogenic cytokines in CD4+ cells. We identified that the endogenous IFNb from serum of RRMS patients induced a significantly lower IFN-inducible gene expression in comparison to healthy controls (HCs). In addition, in-vitro studies have revealed a deficient endogenous and exogenous IFNb signaling in CD4+ cells derived from MS patients. Interestingly, upon inhibition of the endogenous IFNb signaling by silencing interferon regulatory factor (IRF)7 gene expression, the resting CD4+ T cells secreted significantly higher level of IL-17A, IL-17F, IL-21, IL-22 and IL-9, suggesting that endogenous IFNb suppresses the secretion of these pathogenic cytokines. In-vivo recombinant IFNb-1a treatment induced IFNAR1 and its downstream signaling molecules gene expression, suggesting that treatment may reconstitute a deficient endogenous IFNbeta regulation of the CD4+ T-cells pathogenic cytokine production in MS patients.