Fig. 1: NK cell expansion and NK cell function in standard assays.

a NK cell viability of fresh (blue) and cryopreserved (red) NK cells as measured by flow cytometry (n = 9; p = 0.36 by two-sided nonparametric Wilcoxon signed-rank test for paired data). b Fraction of NK cells (single-hatched) and cytotoxic NK cells (double-hatched) within PBMCs before expansion (Day 0; white bars), and after expansion (Day 14) for fresh (blue) and cryopreserved (red) samples (n = 10). The increase in the fraction of NK cells and cytotoxic NK cell after expansion is significant (p = 0.002 for both conditions by two-sided nonparametric Wilcoxon signed-rank test for paired data). Cryopreservation does not decrease the fraction of NK cells (p = 0.49), but decreases the fraction of cytotoxic NK cells (p = 0.004 by two-sided nonparametric Wilcoxon signed-rank test for paired data). c Percentage of CD107a-expressing NK cells for different NK to target cell ratios, as measured in a degranulation assay (n = 8). Control measurements are conducted in the absence of target cells. PMA/Iono is added for positive control experiments. Differences in the degranulation between fresh and cryopreserved NK cells do not reach statistical significance (−Ctrl: p = 0.055, +Ctrl: p = 0.74, 20:1: p = 0.74, 5:1: p = 0.38; two-sided nonparametric Wilcoxon signed-rank test for paired data). d NK cell cytotoxicity as measured in a chromium-release assay for different NK to target cell ratios (n = 10). Differences between fresh to cryopreserved NK cells reach statistical significance for all conditions (20:1: p = 0.014, 10:1: p = 0.006, 5:1: p = 0.004, 2.5:1: p = 0.002; Spearman’s rank-order correlation). For fresh NK cells, there is no significant correlation between NK-to-target cell ratio and cytotoxicity (correlation coefficient ρ = 0.14, p = 0.38; Spearman’s rank-order correlation), but for cryopreserved NK cells, cytotoxicity decreases for lower NK-to-target cell ratios (correlation coefficient ρ = 0.41, p = 0.009; Spearman’s rank-order correlation). Error bars denote 1 sem. Source data are provided as a Source data file.