Superantigen overcomes resistance of IL-6-deficient mice towards MOG-induced EAE by a TNFR1 controlled pathway.

Experimental autoimmune encephalomyelitis (EAE) induced by myelin oligodendrocyte glycoprotein peptide 35–55 (MOG) leads to a chronic form of disease characterized by demyelination, inflammation and gliosis in the central nervous system (CNS). Recently IL-6 and LTα were found to be required for induction of the disease. The main features associated with EAE resistance of IL-6-/- and LTα-/- mice were reduced T cell proliferation and endothelial activation. As shown here treatment of MOG-immunized IL-6-/- mice with staphylococcal enterotoxin B (SEB)reversed their resistance to MOG-induced EAE. SEB failed to restore susceptibility to EAE in LTα-/- mice. The effect of SEB to induce EAE in IL-6-/- mice depends on TNF receptor type 1 (TNFR1) signaling because IL-6/TNF/LTα-/- and IL-6/TNFR1-/- are refractory to SEB. TNFR1 is involved in SEB induced trafficking of T cells into the CNS as evidenced by the failure to up-regulate VCAM-1 on CNS endothelium and lack of accumulation of Vβ8+ T cells in the CNS of IL-6/TNFR1-/- mice upon immunization with MOG and treatment with SEB. The course of SEB triggered EAE in MOG immunized IL-6-/- mice was characterized by reduced severity and duration of clinical manifestations, which were associated with a significant drop of CNS infiltrating neutrophils and MIP-2 expression after peak disease. Taken collectively the effect of SEB to overcome EAE resistance points to a transient IL-6 independent but TNFR1 dependent proinflamatory pathway in EAE pathogenesis and suggests a crucial function for IL-6 in disease perpetuation.