KLRD1 and neoplasm: Our data, that the chronic lack of PD-1 leads to an impairment of anti-tumor and missing self-responses of NK cells, are reminiscent of previous studies showing that short-term blockade of inhibitory NK cell receptors increases their anti-tumor function, whereas longer blockade leads to a reduction of the function (Carlsten et al., 2016; Wagner et al., 2016).