Since IL-15/IL-15Rα produced by tumor cells upregulated PD-1 and CD16 on NK cells and PD-1 on T cells (Figs. 3B,C and 4B) and since NK cells and CD8+ T cells were identified as drivers for immune-mediated tumor cell killing (Fig. 4A), we evaluated whether enhancing the activity of these cells by avoiding PD-1 receptor signaling and stimulating CD16 could facilitate tumor cell killing. Here, PDCD1 is linked to neoplasm.