Regional CNS responses to IFN-γ determine lesion localization patterns during EAE pathogenesis

The localization of inflammatory foci within the cerebellum is correlated to severe clinical outcomes in multiple sclerosis (MS). Previous studies of experimental autoimmune enceph- alomyelitis (EAE), a model of MS, revealed distinct clinical outcomes correlated with the capacity of the animal to produce IFN-γ. Outcomes were linked to localization of inflammatory cells in either the spinal cord (wild type [WT]) or the cerebellum and brain stem (IFN-γ deficient). We demonstrate, using an adoptive transfer system, that the ability of the central nervous system (CNS) to sense pathogenic T cell-produced IFN-γ during EAE initiation determines the sites of CNS pathogenesis. Transfer of WT Th1 cells into IFN-γ receptor-deficient mice results in pathogenic invasion of the brain stem and cerebellum with attendant clinical symptoms, which are identical to the disease observed after transfer of IFN-γ-deficient T cells to WT hosts. Inflammation of the spinal cord associated with classical EAE is abrogated in both IFN-γ-deficient systems. Cotransfer of CNS antigen- specific WT Th1 cells with IFN-γ-deficient T cells is sufficient to restore spinal cord invasion and block cerebellar and brain stem invasion. These data demonstrate that interaction between IFN-γ and host CNS cells during the initiation of EAE can selectively promote or suppress neuroinflammation and pathogenesis.