In addition, we found that both IFNγ −/− and IFNγ +/+ mice of resistant MHC H-2 b haplotype cleared Theiler's virus infection from spinal motor neurons, but whereas IFNγ +/+ H-2 b mice eventually cleared virus from the spinal cord white matter, IFNγ −/− H-2 b mice developed viral persistence in glial cells of the white matter and consequent spinal cord demyelination.