IL-6 is detectable in brain lesions (103) and in the CSF from people with MS (104) and plays critical roles in MS and EAE pathophysiology that include compromising blood-brain barrier integrity in combination with IL-17A (105), cooperating with transforming growth factor-β to drive the differentiation and expansion of auto-reactive TH17 cells (106–109), and damaging myelin (102). Here, IL17A is linked to myeloid sarcoma.