These results suggest the presence of Th9 cells in the CNS of MS patients, where IL-9 could exert a protective role in MS disease by reducing the levels of IL-17 produced by Th17 cells [147] and the expression of the mitochondrial pro-apoptotic factor Bax [149], thus enhancing neuronal survival in organotypic human brain slice cultures [150]. Here, IL17A is linked to myeloid sarcoma.