a, Expression of Ercc1 was measured in tissues from 8–10-month-old Vav-iCre+/−;Ercc1−/fl and Ercc1−/fl control mice (n = 5–7 Vav-iCre+/−;Ercc1−/fl; n = 3–5 Ercc1−/fl, depending on the tissue (see Supplementary Table 3 for sample size details). b, Detection of ERCC1 in splenic lysates from a 9-month-old Vav-iCre+/−;Ercc1−/fl mice and littermate control by immunoblot. c, Superoxide anion levels were measured by electron paramagnetic resonance (EPR) in splenic tissue from 6–8-month-old Vav-iCre+/−;Ercc1−/fl and littermate control mice (n = 5 mice per group). d, e, Expression of the transcription factor NRF (Nfe2l2) and its downstream targets (Cat, Nqo1, Hmox1) measured by qRT–PCR in spleen (d) and bone marrow (e) of Vav-iCre+/−;Ercc1−/fl and littermate control mice at several ages (n = 3 at 3- and 5-months-old; n = 5 8–10-months-old) and in two-year-old wild-type mice (n = 5). f, Catalase activity measured in splenic tissue from 8–10-month-old Vav-iCre+/−;Ercc1−/fl (n = 6) and Vav-iCre+/− (n = 3) mice (Methods). g, Catalase activity in 4-month-old (n = 3) and 24-month-old (n = 6) wild-type mice. h, i, The ratio of reduced to oxidized glutathione (GSH/GSSG) (Methods) (h) and levels of HNE protein adducts (i) measured by ELISA in splenic lysates of Vav-iCre+/−;Ercc1−/fl and littermate control mice at 8–11 months of age (n = 6 mice per group). j, Levels of four cyclopurine adducts in splenic tissue from 8–10-month-old Vav-iCre+/−;Ercc1−/fl mice and littermate controls (n = 4–5 Vav-iCre+/−;Ercc1−/fl; n = 5 Vav-iCre+/−; see Supplementary Table 3 for sample size details) measured by liquid chromatograph–tandem mass spectrometry (LC–MS/MS/MS) (Methods). k, Total splenocyte cell counts from 8–10-month-old Vav-iCre+/−;Ercc1−/fl (n = 14) mice and Vav-iCre+/− (n = 12) mice. l, The absolute number of T (CD4+, CD8+) and B (B220+CD19+) cells in spleens from the same mice (n = 10/4 Vav-iCre+/−;Ercc1−/fl; n = 8/3 Vav-iCre+/− for CD4+ or CD8+/ B220+CD19+ measures, respectively) (Methods). m, Total splenocyte cell counts from young (7-month-old; n = 10) and old (24-month-old; n = 17) wild-type mice. n, The absolute number of CD4+, CD8+ and B220+CD19+ cell in spleens from the same mice (n = 8/3 young WT; n = 17/7 old wild-type mice for CD4+ or CD8+/B220+CD19+ measures, respectively). o, Analysis of CD8+ splenocytes from 8–10-month-old mice for memory (CD44+CD127+), exhaustion (PD-1+) and apoptosis (VAD-FMK+) markers (n = 6 mice per group). p, Thymic weight normalized to total body weight (n = 3 at 3 months old; n = 4–5 at 8–10 months old per group). q, Histology images (20×) of spleen and lymph nodes from 8–10-month-old Vav-iCre mice. Scale bar, 100 μm. GC, germinal centres. Data are mean ± s.d. *P < 0.05, ∞P < 0.01, ∇P < 0.001, #P < 0.0001, unpaired two-tailed Student’s t-test (a, c–e for the 3- and 5-month-old mice, g–p), one-way ANOVA (d, e for the 8–10-month-old mice) or two-way (f) with Tukey’s test.