Figure 3. Impairment in ETC complex I, but not complex IV, reduce Treg suppressive function.

(A) NAD/NADH and (B) ATP measurements in heart tissue from age and gender matched ND6^mut (ETC complex I defect), CO1^mut (ETC complex IV defect) and co-housed wild type control mice (4–6/group). ND6^mut mice show reduced NAD relative to NADH, with normal ATP production. CO1^mut mice are capable of NADH to NAD oxidation, but show impaired ATP production. (C, D) Comparison of the ability of ND6^mut versus control Tregs to suppress proliferation of CFSE-labeled T-effector (Teff) cells in vitro, stimulated with anti-CD3ε mAb and irradiated CD90.2⁻ antigen presenting cells. (C) Representative flow cytometry and (D) cumulative analysis showing Treg from aged ND6^mut mice have weaker suppressive Treg function versus results for WT Treg. Student’s t-test; data pooled from 11 observations and four independent experiments. (E) Comparison of the ability of CO1^mut versus control Tregs shows no difference in suppressive function. (F) Cumulative data; Student’s t-test. Data pooled from 10 observations and three independent experiments. All wild type controls were age- and gender matched. * indicates p<0.05, and error bars indicate SEM.