Contributions
Abstract: P746
Type: Poster Sessions
Abstract Category: Pathology and pathogenesis of MS - Experimental models
Background: Granulocyte-macrophage colony-stimulating factor (GM-CSF), a myeloid cell growth and differentiation factor, plays a critical role in experimental autoimmune encephalomyelitis (EAE), widely used as an animal model of multiple sclerosis. We have recently shown that disruption of GM-CSF signaling exclusively during the effector phase of EAE triggers clinical remission.
Objective: To elucidate the mechanism of action by which GM-CSF drives chronic disability in adoptively transferred EAE
Methods: EAE was induced in naïve WT, Csf2r-/-, CCR1-/- or mixed WT: Csf2r-/- bone marrow chimeric mice by the adoptive transfer of purified myelin-reactive CD4+ Th17 cells. In some experiments, WT adoptive transfer recipients were treated with a CCR1 antagonist. CNS inflammatory cell composition was analyzed by flow cytometry and cell subsets were FACS sorted for qPCR. Chemokines were measured in CNS homogenates via ELISA.
Results: We found reduced expression of transcripts encoding CCL6 in Csf2r-/-, compared with WT, myeloid cells FACS sorted from the CNS of mixed bone marrow chimeric mice during peak EAE. Consistent with this finding, CCL6 was expressed at lower levels in CNS homogenates, and in CNS myeloid cells, harvested from Csf2r-/- versus WT adoptive transfer recipients at peak EAE. GM-CSF directly stimulated upregulation of CCL6, and its cognate receptor, CCR1, in cultured splenic monocytes/ macrophages and neutrophils. Reminiscent of the clinical course of Csf2r-/- transfer recipients, WT recipients treated with a CCR1 antagonist underwent remission, whereas their vehicle treated counterparts developed chronic paraparesis. The frequency of granulocytes was disproportionately low in the CNS infiltrates of both Csf2r-/-adoptive transfer recipients and WT adoptive transfer recipients treated with the CCR1 antagonist.
Conclusions: This study shows that GM-CSF drives chronic disability in mice with passive EAE by promoting the sustained recruitment of myeloid cells to the CNS by a CCR1/ CCL6 dependent pathway. CCR1 and its ligands should be considered as candidate therapeutic targets in chronic MS.
Disclosure: Dr. Benjamin Segal and Patrick Duncker have no conflicts of interest to disclose.
Abstract: P746
Type: Poster Sessions
Abstract Category: Pathology and pathogenesis of MS - Experimental models
Background: Granulocyte-macrophage colony-stimulating factor (GM-CSF), a myeloid cell growth and differentiation factor, plays a critical role in experimental autoimmune encephalomyelitis (EAE), widely used as an animal model of multiple sclerosis. We have recently shown that disruption of GM-CSF signaling exclusively during the effector phase of EAE triggers clinical remission.
Objective: To elucidate the mechanism of action by which GM-CSF drives chronic disability in adoptively transferred EAE
Methods: EAE was induced in naïve WT, Csf2r-/-, CCR1-/- or mixed WT: Csf2r-/- bone marrow chimeric mice by the adoptive transfer of purified myelin-reactive CD4+ Th17 cells. In some experiments, WT adoptive transfer recipients were treated with a CCR1 antagonist. CNS inflammatory cell composition was analyzed by flow cytometry and cell subsets were FACS sorted for qPCR. Chemokines were measured in CNS homogenates via ELISA.
Results: We found reduced expression of transcripts encoding CCL6 in Csf2r-/-, compared with WT, myeloid cells FACS sorted from the CNS of mixed bone marrow chimeric mice during peak EAE. Consistent with this finding, CCL6 was expressed at lower levels in CNS homogenates, and in CNS myeloid cells, harvested from Csf2r-/- versus WT adoptive transfer recipients at peak EAE. GM-CSF directly stimulated upregulation of CCL6, and its cognate receptor, CCR1, in cultured splenic monocytes/ macrophages and neutrophils. Reminiscent of the clinical course of Csf2r-/- transfer recipients, WT recipients treated with a CCR1 antagonist underwent remission, whereas their vehicle treated counterparts developed chronic paraparesis. The frequency of granulocytes was disproportionately low in the CNS infiltrates of both Csf2r-/-adoptive transfer recipients and WT adoptive transfer recipients treated with the CCR1 antagonist.
Conclusions: This study shows that GM-CSF drives chronic disability in mice with passive EAE by promoting the sustained recruitment of myeloid cells to the CNS by a CCR1/ CCL6 dependent pathway. CCR1 and its ligands should be considered as candidate therapeutic targets in chronic MS.
Disclosure: Dr. Benjamin Segal and Patrick Duncker have no conflicts of interest to disclose.