HLA-C and leukemia: The ligand for KIR2DS5 receptor is not known, however it has been observed that the simultaneous presence of KIR2DS5 gene and HLA-C-encoded epitopes for both KIR2DL1 and KIR2DL2/3 receptors significantly decreased leukemia-free survival of hematopoietic stem cell-transplanted patients [33], which could suggest KIR2DS5 interaction with HLA-C.