PDCD1 and myeloid sarcoma: Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system mediated by immune dysregulation, mainly characterized by motor and sensory disorders, ataxia, etc. PD-1/PD-L1 signaling plays a key role in the pathogenesis of MS by downregulating the immune responses of autoreactive T cells in the central nervous system [56].