Mitochondrial fusion maintains NK cell survival and cellular fitness. (A) Percentage of TMRM⁺ cells in NKBr and NKDim cells (data from 7 HDs). (B-C) Quantification of TMRM in CD57⁺ NKDim and CD57⁻ NKDim cells in CMV⁺ and CMV⁻ donors: representative plots (B) and quantification (C) (geometric mean fluorescence intensity [MFI]). (D-G) NKDim cells were cultured with IL-15 or IL-15/12/18 for 12 days. Mdivi-1 was added or not to NKDim cells from CMV⁻ donors. (D) Growth curves of NKDim cells isolated from CMV⁺ and CMV⁻ HDs and cell numbers at end point. (E) Representative fluorescence-activated cell sorting (FACS) analysis of NKG2C and NKG2A and percentage of NKG2C⁺NKG2A⁻ cells in the indicated culture conditions at day 12. Quantification by FACS of IFN-γ and percentage of IFN-γ⁺ cells (F) and CD107a⁺ cells (G) at day 12 (data are mean ± SEM; data summarized from 3 independent experiments with at least 2 HDs each). P > .05 was considered not significant (ns). *P < .05, **P < .01, ***P < .001, ****P < .0001 using 2-way analysis of variance with Tukey’s correction.