Figure 3.

Human NK cells labeled with ¹⁹F maintain their cytotoxic function in vitro. (A) Sorted human NK cells were cultured with ¹⁹F for 24 h. Extra ¹⁹F not taken up by NK cells was washed out, then NK cells (E: effectors) were cultured with ⁵¹Cr-labeled K562 tumor (T: target) for 4 h at 37°C at different E:T ratios to determine their percent lysis of tumor cells, n = 5. Values represent the mean ± SEM of one of four independent experiments tested by two-way ANOVA, with no significant difference seen. (B–D) NK cells labeled with 4 mg/mL ¹⁹F or unlabeled were stained for flow cytometry intracellularly for IFNγ and granzyme B or isotype control, n = 5 donors. (B) Compiled percentage or (C) representative flow plots or (D) MFI in isotype control, IFNγ and Granzyme B by unlabeled and ¹⁹F-labeled NK cells is illustrated. (E) Human IFNγ production was determined by ELISA in NK cells unlabeled or labeled with ¹⁹F at 2 mg/mL or 4 mg/mL ¹⁹F for 24 h or 48 h, n = 3, no difference was observed. Dot plots are representative of one of at least five experiments with reproducible results. Bar graph values represent the mean ± SEM of one of five independent experiments tested by two-way ANOVA. p < 0.05, n.s = not significant.