IL-12 is responsible for the raised IFN-γ secretion known to exacerbate MS, unlike in EAE, where IL-12 but not IFN-γ exacerbated EAE (Panitch et al., 1987; Balashov et al., 1997; Leonard et al., 1997; Segal et al., 1998). This evidence concerns the gene IFNG and myeloid sarcoma.