PDCD1 and neoplasm: Apart from the wide-spread use of checkpoint inhibitors in melanoma, lung cancer etc., agents blocking the PD-1/PD-L1 axis are currently being evaluated in clinical trials on both hematologic and solid tumors as monotherapy or in combination with other agents, including other forms of immune checkpoint blockade, such as anti-panKIR2D and anti-NKG2A antibodies in the case of HLA-I+ tumor cells (Moretta et al., 1996, 2001; Cosman et al., 1997; Braud et al., 1998; Sivori et al., 2004; Marcenaro et al., 2008; Di Vito et al., 2019).