Some of the known NCRs ligands (such as the influenza virus HA, recognized by NKp46 or NKp44) allow for the NK-mediated recognition of virus-infected cells, while others (such as BAT3/BAG6 and B7-H6, ligands for NKp30, or the isoform of mixed-lineage leukemia protein-5, termed 21spe-MLL5, and PCNA, ligands for NKp44) allow for the NK-mediated recognition of tumor cells. Here, PCNA is linked to neoplasm.