Memory B cells have reduced mitochondrial content and require Bnip3 and Nix for mitochondrial homeostasis. (A) Intracellular staining of Tom20 in GC and memory B cells. Dashed line: isotype control (n=5 mice per group). Data are representative of three independent experiments and are presented as mean ± s.e.m. **P < 0.01. (B) Flow cytometry analysis of Mitotracker Green staining in germinal center (GC) and memory B cells (MBC). Dashed line: isotype control (n=4 mice per group). Data are representative of three independent experiments and are presented as mean ± s.e.m. **P < 0.01. (C, D) Real-time RT-PCR for Beclin 1, Atg5, Atg7 (C), Nix and Bnip3 (D) in GC and memory B ( n=3). Data are representative of two independent experiments and are presented as mean ± s.e.m. **P < 0.01; ns, not significant. (E) Analyses of NP-specific memory B cells 8 weeks after immunization in the spleens of wild type (WT), B/Nix–/–, Bnip3−∕−, B/Nix–/–Bnip3−∕− (DKO) mice (n=5 mice per group) by flow cytometry. Data are representative of three independent experiments and are presented as mean ± s.e.m. **P < 0.01; ns, not significantly different.