Differential expression of suppressors of cytokine signaling-1 and -3 and related cytokines in central nervous system during remitting versus non-remitting forms of experimental autoimmune encephalomyelitis

SJL mice exhibit a relapsing-remitting course of experimental autoimmune encephalomyelitis (EAE), whereas C57BL/6 (B6) mice display a more chronic course without complete remissions. Suppressor of cytokine signaling (SOCS)-1 and SOCS-3 are members of a family of inducible intracellular proteins that negatively regulate cytokine signaling in cells of hematopoietic origin and may influence the T_h1 to T_h2 balance. SOCS-1 and SOCS-3 are induced by cytokines that are known to be up-regulated during EAE, including IFN-gamma (IFN-g) and IL-6, respectively. To test the hypothesis that the level of induction of SOCS-1 and SOCS-3 correlates with the course of EAE, mRNA levels were compared in spinal cords of SJL and B6 mice during discrete stages of disease. SOCS-1 and SOCS-3 were elevated throughout active disease in both strains. At peak EAE, SOCS-1 was higher and SOCS-3 was lower in B6 cords compared with SJL cords. This correlated with greater expression of the T_h1 cytokine, IFN-g, and less of the T_h2 cytokine, IL-10, in B6 cords relative to SJL cords during onset and peak disease. SOCS-3 inducers in the IL-6 family were expressed differentially between the strains. IL-6 and leukemia inhibitory factor were higher at onset in B6 cords whereas ciliary neurotrophic factor was increased in SJL cords during peak disease. Expression of fibroblast growth factor-2, which may be involved in remyelination, was higher in SJL cords at peak. Comparison of these models suggests that cytokine autoregulatory mechanisms involving SOCS may play a role in determining the course of EAE.