Because CD8+ T cells predominate, expand and have an activated cytotoxic phenotype in the MS brain (Babbe et al., 2000; Serafini et al., 2007; van Nierop et al., 2017; Machado-Santos et al., 2018), it is likely that this immune cell subset represents the major local source of IFNγ. The gene discussed is IFNG; the disease is myeloid sarcoma.