Antagonistic antibodies against other inhibitory receptors and ligands, notably the PD-1/PD-L1 axis, have subsequently been demonstrated effective in tumor immunotherapy, resulting in Food and Drug Administration approval (Iwai et al., 2002; Brahmer et al., 2012; Topalian et al., 2012a, 2012b; Powles et al., 2014). This evidence concerns the gene PDCD1 and neoplasm.