Neutrophil-specific Socs3 deficiency induces brain-targeted experimental autoimmune encephalomyelitis with increased cerebellar neutrophils

Abstract Multiple sclerosis (MS) is associated with a dysregulated JAK/STAT signaling pathway. Suppressors of cytokine signaling (SOCS) negatively regulate the JAK/STAT pathway. MS patients with disease affecting the cerebellum display rapid progression and poor prognosis. Previous data from our laboratory demonstrates a severe, brain-targeted form of experimental autoimmune encephalomyelitis (EAE) in mice lacking Socs3 in myeloid cells (Socs3ΔLysM), with increased cerebellar infiltration of primed neutrophils. Here, we induced EAE in mice lacking Socs3 specifically in neutrophils (Socs3ΔLy6G; n=26) and Ly6G−/+ control mice (n=13), and examined disease progression, neutrophil populations and CD4+ T-cell polarization at disease peak. Ly6G−/+ mice exhibited clinical signs of classical EAE, whereas Socs3ΔLy6G mice exhibited clinical signs of brain-targeted EAE, similar to Socs3ΔLysM mice. An analysis of the cerebellar cell infiltrate in Socs3ΔLy6G mice demonstrated an increased cellularity (p=0.005), which was comprised of both an increase in the percentage (p=0.020) and total number (p<0.001) of cerebellar neutrophils. Neutrophils from Socs3ΔLy6G mice exhibited a primed phenotype with increased surface expression of CD11b (p=0.084) and reduced expression of CD62L (p<0.001). Additionally, Socs3ΔLy6G mice exhibited an increase in the percent of cerebellar CD4+ T-cells (p=0.018) and a shift toward IFN-γ-producing Th1 CD4+ T-cells (p=0.012). These data conclusively document that neutrophil-specific deficiency of Socs3 is sufficient to induce brain-targeted EAE. Future studies will identify targets to dampen the role of neutrophils in brain-targeted autoimmune neuroinflammation.