Figure 5. Immunosenescence, Stress Defenses and Metabolic Activity.

(A) Total T cells (CD3⁺) were analyzed by flow cytometry as % of total peripheral lymphocytes. N=8–12, 5 and 24 months, males.

(B) Ratio of naive to memory T cells (CD44⁻/CD44⁺), and (C) ratio of helper to killer T cells (CD4⁺/CD8⁺) were measured in the same samples.

(D) Proportions of common myeloid and lymphoid progenitors (CMP, CLP), and short-term and long-term hematopoietic stem cells (ST-HSC, LT-HSC) were scored as % of Lin⁻ cells in bone marrow (tibia and femur). N=6, 16 months, females. Normalized to Myc^+/+ for each comparison.

(E) Ratio of CLP to CMP, and (F) ratio of ST-HSC to LT-HSC in the same samples.

(G) 53BP1-positive cells were visualized by IF in liver sections. N=5–6, 5 and 25 months, males.

(H) Apoptotic cells in liver were identified by IF with an antibody to cleaved caspase-3. N=6–8, 5 and 22 months, females.

(I) F₂ isoprostane levels were measured in liver extracts using gas chromatography and mass spectrometry. N=4–7, 5 and 23–27 months, males.

(J) O₂ consumption by young animals over a 24 hour period. Statistical significance in was computed using two-way ANOVA (time, genotype). Genotype factor was significantly different; p<0.001. N=8, 5 months, both sexes.

(K) O₂ consumption by old animals. P(genotype) <0.001. N=7–8, 17–22 months, males.

See also Figure S5.