**Kinetics for γ-H2AX foci loss in macaque lymphocytes after total body irradiation.**(**A**) Representative images of macaque lymphocytes in Sham-irradiated (Sham) and 0.3, 1, 2, 3, 7 and 10 days (d) after 8.5 Gy-TBI. As previously observed with blood samples irradiated *ex-vivo*, the γ-H2AX foci were fewer and fainter in neutrophils than in lymphocytes. Green, γ-H2AX; red, DNA stained with PI. Arrowheads indicate neutrophils. (**B**) γ-H2AX foci distribution in lymphocytes taken from individual animals subjected to TBI. The rows from top to bottom show the focal distributions from individual animals after 8.5 Gy-TBI (6 macaques E25 to E30) and Sham-TBI (2 macaques E23 and E24, noted S), 6.5 Gy-TBI (6 macaques E15 toE20) and Sham-TBI (2 macaques E21 and E22, noted S), 3.5 Gy-TBI (6 macaques E01to E06) and Sham-TBI (2 macaques E07and E08, noted S), and 1 Gy-TBI (6 macaques E09 to E14) and sham-TBI (2 macaques E21 and E22, noted S). Results from the sham-IR are shown with red lines (noted S). The columns from left to right correspond to the different sampling times post-TBI, 0.3 d (1 and 3.5 Gy), 1 d (1 , 3.5 , 6.5 and 8.5 Gy), 2 d (1 , 3.5 , 6.5 and 8.5 Gy), and 4 d (3.5 , 6.5 and 8.5 Gy). (**C**) Values for γ-H2AX foci per cell *vs* days after the indicated TBI doses. The data for the TBI treated cohorts (blue bars) and sham treated controls for each cohort (red bars) are plotted on a log scale to bring out the details concerning differences between the TBI and sham treated animals. The data are shown as mean numbers of γ-H2AX foci per lymphocyte from each cohort ± standard deviations (n = 2 for Sham irradiated samples; n = 6 for TBI-irradiation, except 16 days after 3.5 Gy, n = 3 and 11 days after 8.5 Gy; no SD was determined 14 days after 8.5 Gy as data were prepared from 1 animal). (**D**) Foci per cell values in lymphocytes taken at the noted time (Pre = the day before TBI) and plotted *vs* TBI dose. Data are means ± standard deviations (n = 6). Equations for trendlines and R-squared values are y = −0.005x+0.096 / R^{2} = 0.225 for Pre-IR; y = 3.167x−0.578 / R^{2} = 0.980 for 0.3 d; y = 0.672x−0.034 / R^{2} = 0.996 for 1 d; y = 0.286x+0.014 / R^{2} = 0.993 for 2 d and y = 0.158x+0.097 / R^{2} = 0.956 for 4 d. Asterisks in (**C**) denote statistically difference between TBI-and sham-irradiated macaques (P<0.05, t-test). Detailed statistical analysis is shown in . Numbers in (**C**) for the 6.5 and 8.5 Gy panels correspond to the numbers of animals alive after TBI at the indicated time (no number indicates that all 6 TBI-irradiated animals are alive).