PDCD1 and myeloid sarcoma: To further investigate the role of PD-1 and its cognate ligand PD-L1 in MS patients, we quantified mPD-1 on T cell subsets, as well mPD-L1 on APCs (B cells, dendritic cells and monocytes) and NK cells (Fig. 2A), in PBMCs obtained from RRMS patients and controls using a standardized immunophenotyping procedure (Fig. 2, Supplementary Fig. 2, Table 1 and Supplementary Tables 1 and 2).