KIR2DS1sp NK cells in HLA-C2 homozygous donors are not hyporesponsive to stimulation with IL-12 and IL-15. (A) Representative example of IFN-γ production by NKG2A⁻KIR⁻ (left panels) and NKG2A⁻KIR2DS1sp (right panels) NK cells from a HLA-C2 homozygous donor after culture in medium alone (top panels), and after stimulation with IL-12 and IL-15 in combination (bottom panels). (B) Paired comparison of the frequency of IFN-γ–producing cells within NKG2A⁻KIR⁻ and NKG2A⁻KIR2DS1sp NK cells from HLA-C1 homozygous (left panel) and HLA-C2 homozygous (right panel) donors.