IL-2 alters the expression of inhibitory and stimulatory receptors on primary human NK cells. (A–C) CD3⁻CD7⁺CD56⁺ primary human NK cells were sorted to avoid contamination with myeloid cells. Representative plots with side scatter vs. CD3 (left column), CD7 (middle column), or CD56 (right column) are shown. Rows show the isotype controls (A) and CD3⁻CD7⁺CD56⁺ NK cells before (B) and after 5 d of IL-2 stimulation (C). (D) Whole transcriptome sequencing of CD3⁻CD7⁺CD56⁺ primary NK cells was performed without IL-2 and after 5 d of IL-2 stimulation (heatmap shows row z-scores for the normalized expression of genes at least twofold differentially expressed among groups; FDR < 0.1, n = 3 per group). (E) Changes in gene expression of inhibitory and stimulatory NK receptors during 5 d of IL-2 stimulation (heatmap shows row z-scores for the normalized expression of selected NK cell receptors). All depicted genes are significantly (FDR < 0.1) differentially expressed. Changes are at least twofold, except for SIGLEC7 (log2 fold change = 0.84). (F) Whole transcriptome sequencing of primary human NK cells and NK cell lines were conducted after 24 h of IL-2 stimulation (heatmap shows z-scores for normalized expression of genes that were at least twofold differentially expressed in any four NK cell line compared with primary NK cells). (G) Principal-component analysis showing the distance of primary NK cells to all NK cell lines and the clustering of NKL with its sublines NK-RL12 and NK-CT604. (H and I) Gene expression of stimulatory NK cell receptors (H) and inhibitory NK cell receptors (I; heatmaps show z-scores for normalized expression).