Kinetics of BrdU-labeled lymphocytes in blood. Graphs represent the kinetics for total CD4 and CD8 T cells (A), and naive, central memory, effector memory, and activated subsets of CD4 (B) and CD8 (C) T cells. The x-axis represents the days following the BrdU infusion; and the y-axis, in log₁₀ scale, the percentage of BrdU-positive cells as detected by flow cytometry. Data represent the geometric mean (± SD) for the first infusion for all 41 patients (panel A; Table 1, dataset 2) and the 22 patients for whom the BrdU kinetics of the subsets were also available (panels B-C; Table 1, dataset 3).