T helper (Th)1 cells were initially thought to be the only effector (memory) T cells (TEM) [5,6] capable of mediating inflammatory demyelination in MS [7]; however, the discovery of Th17 cells has led to the idea that IL-17 produced by CD4+ or CD8+ T cells specific to myelin proteins (likely in response to IL-23 and granulocyte monocyte-colony stimulating factor, GM-CSF) plays a preponderant role in the autoimmune demyelinating disease found in humans and mice [8-15]. This evidence concerns the gene IL17A and myeloid sarcoma.