PD-1 is also expressed on the surface of other cells such as B cells, Natural Killer (NK) cells, Dendritic cells (DCs), myeloid cells and therefore it is likely that anti-PD-1 antibodies can also stimulate anti-tumor immunity increasing antibody production, activating NK cells or reducing immunosupressive activity of “myeloid derived suppressor cells” (MDSCs) [50,51,52]. Here, PDCD1 is linked to neoplasm.