KIR⁺ CD8 T cells are not educated by cognate HLA class I ligands. (A) Staining for KIR2DL1/S1, KIR2DL2/3/S2, KIR3DL1, and tetramer-defined CMV-specific cells within CD45RA⁺CD57⁺ CD8 T cells in 1 CMV-seropositive healthy individual. (B) Frequency of pan-KIR⁺ cells within CMV tetramer–positive and –negative CD45RA⁺CD57⁺ CD8 T cells summarized for 6 CMV seropositive healthy individuals (*P < .05, paired t test). (C) Representative stainings for CD107a, IFN-γ, and TNF-α on CD45RA⁺CD57⁺ CD8 T cells from 1 healthy individual after the indicated stimulations for 6 hours. (D) Frequency of total responding (TNF-α, CD107a, or IFN-γ) cells within KIR⁻ and KIR⁺ CD45RA⁺CD57⁺ CD8 T cells (n = 13; *P < .05, Wilcoxon matched pairs test; mean). (E) Frequency of cells responding with TNF-α, CD107a, and IFN-γ within KIR⁻, single-KIR⁺ or double-KIR⁺ CD45RA⁺CD57⁺ CD8 T cells (n = 13, 25, and 8, respectively; ***P < .01, *P < .05, Kruskal-Wallis test with Dunn posttest; mean). (F) Frequency of total responding cells in KIR⁻ and single KIR⁺ cells with or without a self-ligand present in the host for the respective KIRs (n = 13, 12, and 12, respectively; n.s. indicates not significant, Wilcoxon matched pairs test; mean). (G) Distribution of responding cells into single, double, and triple function for self and nonself single KIR⁺ cells (n = 12; n.s. indicates not significant, Wilcoxon matched pairs test; mean). (C-G) KIR2DL1 and KIR2DL3 were analyzed.