IL-23 and IL-17 are both expressed in MS lesions,[22] and increased expansion of Th17 cells is believed to contribute to the infiltration of myelin-specific T cells into the CNS [Figure 1].[23] In EAE model, the suppression of Th17 lymphocytes has been shown to reduce the clinical expression of disease, although this is becoming an area of controversy.[24, 25]. This evidence concerns the gene IL17A and myeloid sarcoma.