OPCs also express antigens CD273 and CD274 (also known as programmed death ligand (PD-L) 2 and PD-L1, respectively) (24, 27, 43) (reviewed by Cabeza-Fernández et al (50),). When exposed to cerebrospinal fluid (CSF) from MS patients in the phase of progressive MS (pMS), OPCs upregulate PD-L1, which in turn suppresses T cell-induced inflammation (43). Here, PDCD1LG2 is linked to myeloid sarcoma.