In both MS and EAE animal models, inflammatory Th cells, once recruited to the CNS, produce cytokines such as TNF-α, IL-17, GM-CSF and IFN-γ (11) that activate astrocytes, which in turn acquire a reactive phenotype, proliferate, form glia scar (29, 30) and produce several cytokines and chemokines favouring the recruitment of leucocytes and inflammatory Th cells into the CNS parenchyma (25, 26, 31–34). The gene discussed is IFNG; the disease is myeloid sarcoma.