['Glatiramer acetate (GA; Copaxone), a disease-modifying therapy for multiple sclerosis (MS), promotes development of anti-inflammatory (M2, type II) monocytes that can direct differentiation of regulatory T cells. We investigated the innate immune signaling pathways that participate in GA-mediated M2 monocyte polarization.', 'Monocytes were isolated from myeloid differentiation primary response gene 88 (MyD88)-deficient, Toll-IL-1 receptor domain-containing adaptor inducing interferon (IFN)-β (TRIF)-deficient, IFN-α/β receptor subunit 1 (IFNAR1)-deficient, and wild-type (WT) mice and human peripheral blood. GA-treated monocytes were stimulated with Toll-like receptor ligands, then evaluated for activation of kinases and transcription factors involved in innate immunity, and secretion of proinflammatory cytokines. GA-treated mice were evaluated for cytokine secretion and susceptibility to experimental autoimmune encephalomyelitis.', 'GA-mediated inhibition of proinflammatory cytokine production by monocytes occurred independently of MyD88 and nuclear factor-κB, but was blocked by TRIF deficiency. Furthermore, GA did not provide clinical benefit in TRIF-deficient mice. GA inhibited activation of p38 mitogen-activated protein kinase, an upstream regulator of activating transcription factor (ATF)-2, and c-Jun N-terminal kinase 1, which regulates IFN regulatory factor 3 (IRF3). Consequently, nuclear translocation of ATF-2 and IRF3, components of the IFN-β enhanceosome, was impaired. Consistent with these observations, GA inhibited production of IFN-β in vivo in WT mice, but did not modulate proinflammatory cytokine production by monocytes from IFNAR1-deficient mice.'] Does glatiramer acetate treatment negatively regulate type I interferon signaling?