Therefore, we analyzed the effect of KIR2DS4wt copy number on frequency of expression: as two copies, as one copy in the presence of KIR2DS4del, or as one copy in the presence of KIR2DS1. KIR2DS4 frequency on dNK cells is similar in these different genetic backgrounds, suggesting that an altered frequency of KIR2DS4+ dNK cells in KIR2DS1+KIR2DS4+ individuals is not the mechanism by which KIR2DS4 provides protection against pregnancy disorders (Supplemental Fig. 3D). This evidence concerns the gene KIR2DS4 and pregnancy disorder.