PDCD1 and myeloid sarcoma: The number of PD-1+CD4+ T cells, PD-1+CD8+ T cells, PD-L1+ interleukin (IL)-10+CD14+ cells, and PD-L1+IL-10+CD19+ cells in MS patients are significantly increased during the remitting phase compared with the relapsing phase, indicating that PD-1/PD-L1 also plays an immunosuppressive role in MS.