The production of IFN-γ was not attributed to previously reported contamination of dendritic cells (DCs) during NK cell preparation or a response to IL-12 secreted by HLA-G-stimulated myeloid cells (Supplementary Fig. S7a, b).27 Histochemical assays verified widely distributed KIR2DL4 staining in HER2-positive breast cancer specimens, suggesting its abundant expression on infiltrating NK cells in tumor tissues (Fig. 2e, f). This evidence concerns the gene KIR2DL4 and breast cancer.