Characterization of human NK cell KIR repertoires. (A) 14-color flow cytometry panel for assessment of KIR2DL1, KIR2DL2/S2, KIR2DL3, KIR3DL1, KIR2DS1, KIR2DS4, and KIR3DL2 expression in CD56^dim NK cell subsets expressing NKG2A, NKG2C, and/or CD57. Representative examples of stainings in KIR haplotype A homozygous and haplotype B/X donors are shown. (B) Frequency of CD56^dim NK cells expressing the 7 analyzed KIRs and the 128 possible combinations thereof in 199 healthy donors. The presence of one KIR in a combination is represented by a color code below the graph: 2DL1 (dark blue), 2DL2/S2 (purple), 2DL3 (red), 2DS1 (light blue), 2DS4 (orange), 3DL1 (green), and 3DL2 (black). Red dots represent statistical outliers as defined by the Chauvenet criterion (see supplementary Information). (C) Observed frequencies of NK cells expressing 2 KIRs were compared with those expected from the product rule. The black line represents a perfect match between observed and expected values. The red line represents a 1.5-fold deviation from the product rule. Red dots represent statistical outliers as defined in (B).