A recent study demonstrated that MS patient-derived CD4+ T cells injected into demyelinated mouse CNS show high variability in their ability to support remyelination (El Behi et al., 2017), leading to the tantalizing possibility that the inter-patient variation in remyelination efficiency in MS might reflect diverging capacity of Tregs to stimulate remyelination. This evidence concerns the gene CD4 and myeloid sarcoma.