We find that in MS patients a lower fraction of Treg cells expresses the FoxP3-E2 isoform, compared to healthy donors, and this may deprive Treg cells of a further level of immunoregulation, through the inability to inhibit the transcription factors RORα and RORγt and the consequent failure to prevent the development of proinflammatory cells. This evidence concerns the gene FOXP3 and myeloid sarcoma.