Ciliobrevin D inhibits granule convergence in NK cells. Fixed-cell confocal microscopy of YTS (A), NK92 (B), and eNK (C) cells conjugated with their respective target cells after DMSO or ciliobrevin D treatment (100 µM). Red, anti-perforin; blue, 721.221 or K562 cells; green, anti–α-tubulin. Quantitative analyses of the mean lytic granule distance from the MTOC and its SD are shown as a feature of the degree of granule convergence in YTS (D and G), NK92 (E and H), and eNK (F and I) cells. Data represent pooled results from two independent experiments for YTS cells and NK92 cells and two healthy donors for eNK cells (n > 20 cells/group). Error bars show ± SD. **, P < 0.01; ****, P < 0.0001.