Interestingly, CLL cells prevent the generation of an effective anti-tumor T cell-mediated response and avoid killing by both promoting the expression of the immune checkpoint inhibitors programmed cell death-1 (PD-1) and cytotoxic T lymphocyte antigen-4 and producing immunosuppressive factors that impair the ability of CTLs to form functional ISs [14,15,16]. Here, PDCD1 is linked to neoplasm.