KIR2DL4 and neoplasm: Nonetheless, KIR2DL4 neutralization reduced PD-L1 levels in tumor tissues (Fig. 6h), a finding in agreement with the aforementioned report that KIR2DL4 unassociated with HLA-G promoted IFN-γ secretion by NK cells and that IFN-γ upregulated PD-L1 on tumor cells (Figs. 3e and 5a).