However, an opposing reduction in brain and spinal cord IFN-γ mRNA during the development of EAE (Sakurai et al., 2002) suggests that IDO activity may negatively regulate the survival of IFN-γ-producing T helper type 1 (Th1) cells, thought to be a primary pathogenic T-cell subset in both MS and EAE. This evidence concerns the gene IFNG and myeloid sarcoma.