A small fraction of peripheral blood NK cells displays a cytokine-induced memory-like phenotype. (A) Dot plot (left) of selected markers of interest within unstimulated cells only (columns) across the different clusters (rows). The size of the dot represents the percentage of cells expressing the markers, and the color encodes the average scaled expression values. Heat map (right) of the same markers of interest within unstimulated cells only. Clusters are plotted in columns, and genes are shown in rows. Gene expression is color coded, using average scaled expression values per cluster, based on a z-score distribution, ranging from low expression (purple) to high expression (yellow). (B) Expression distribution of each cluster and stimulation condition (violin plots) specifically of granzyme B (GZMB) expression. The shape represents the distribution of cells based on their log(+1) expression values. The color scale represents the mean expression. (C) Module score for each NK cell cluster at the single-cell level, defined using CIML markers.28 Module scores were calculated for unstimulated cells only. Violin plots represent the distribution of the module scores for each cluster, and the error bars represent median and interquartile range. One-way analysis of variance with Bonferroni’s multiple comparison. Nonsignificant (n.s) P > .05; *P < .03; **P < .02; ***P < .0002; ****P < .0001. (D) Comparison of average gene expression values for cluster 6 between unstimulated and IL-2–stimulated cells. Genes with a fold change >0.5 and Bonferroni-corrected P < .05 are highlighted. (E) Selected GO terms using all conserved markers upregulated within this cluster with an adjusted P < .05. No markers were downregulated within this cluster at this significance threshold.