Longitudinal analysis of T-cell proliferation and T-cell numbers in SIVmac239-infected macaques. The percentage of proliferating (Ki67⁺) CD4⁺ (dark green, ○) and CD8⁺ T cells (light green, ♦) in peripheral blood (A,C,E,G,I,K) and plasma IL-7 levels (red, ▪) as fold change from the baseline are plotted for macaques RM1, RM2, RM3, RM4, RM5, and RM6. Absolute numbers of CD4⁺ (dark blue, ▿) and CD8⁺ T cells (light blue, ▴; B,D,F,H,J,L) are given as markers of T-cell homeostasis. Dotted horizontal lines indicate preinfection levels of CD4⁺ (dark blue) and CD8⁺ (light blue) T cells that represent the homeostatic T-cell levels in the absence of SIV infection. The nonthymectomized macaques are shown in panels A-F and the thymectomized macaques in panels G through L.