IL17A and myeloid sarcoma: As a signature cytokine of Th17 cells, IL-17A (referred to as IL-17 hereafter) is significantly elevated in MS patients’ cerebrospinal fluid (CSF) (Kostic et al., 2014) and induces demyelination (Li et al., 2013; Waisman et al., 2015; Wang et al., 2017), due to its proinflammatory nature and direct toxicity on OPCs/Ols, as well as strong inhibitory effects on OPC maturation (Paintlia et al., 2011; Kang et al., 2013).