In vivo BrdU labeling of bone marrow cells in a rhesus macaque. (A) Bone marrow cells obtained from 6 distant bones (right and left humeri, femurs, and tibias) 24 hours after a single dose (60 mg/kg) of BrdU. The cells were stained for the presence of BrdU and Ki-67. Ki-67 was used to better distinguish BrdU⁺ cells. Numbers in the top right quadrants indicate the percentages of BrdU⁺ Ki67 ^bright bone marrow cells. (B) In vivo BrdU labeling does not affect total white blood cell counts. The total white blood cell (WBC) number in blood was monitored after BrdU injection in 7 uninfected (○) and 9 SIV/SHIV-infected (●) rhesus monkeys. Data show means ± SDs of each group per time point. Statistical analysis was performed by a repeated measure ANOVA. Data at each time point were also compared with data at time point 0 by a Dunnett test.