Galectin-1 is essential for the induction of MOG35-55-based intravenous tolerance in experimental autoimmune encephalomyelitis

In experimental autoimmune encephalomyelitis (EAE), intravenous (i.v.) injection of the antigen, myelin oligodendrocyte glycoprotein-derived peptide, MOG(35-55), suppresses disease development, a phenomenon called i.v. tolerance. Galectin-1, an endogenous glycan-binding protein, is upregulated during autoimmune neuroinflammation and plays immunoregulatory roles by inducing tolerogenic dendritic cells (DCs) and IL-10 producing regulatory type 1 T (Tr1) cells. To examine the role of galectin-1 in i.v. tolerance, we administered MOG(35-55)-i.v. to wild-type (WT) and galectin-1 deficient (Lgals1(-/-)) mice with ongoing EAE. MOG(35-55) suppressed disease in the WT, but not in the Lgals1(-/-) mice. The numbers of Tr1 cells and Treg cells were increased in the CNS and periphery of tolerized WT mice. In contrast, Lgals1(-/-) MOG-i.v. mice had reduced numbers of Tr1 cells and Treg cells in the CNS and periphery, and reduced IL-27, IL-10, and TGF-beta 1 expression in DCs in the periphery. DCs derived from i.v.-tolerized WT mice suppressed disease when adoptively transferred into mice with ongoing EAE, whereas DCs from Lgals1(-/-) MOGi. v. mice were not suppressive. These findings demonstrate that galectin-1 is required for i.v. tolerance induction, likely via induction of tolerogenic DCs leading to enhanced development of Tr1 cells, Treg cells, and downregulation of proinflammatory responses.