While KIR2DL4 may serve as an activating or inhibitory receptor23, both ILT2 and KIR2DL4 share the same ligand, HLA-G, a non-classical HLA molecule first identified as a key regulator of foetal–maternal tolerance24 and now recognised to play a regulatory role in suppressing immunity during infection, transplantation, autoimmunity and cancer25. This evidence concerns the gene KIR2DL4 and infection.