CD4 and infection: These increases involved CD4+ T cells (P = 0.0009, acute, and P = 0.0004, chronic), and to a lesser extent CD8+ T cells (P = 0.057 and P = 0.09) (Figure 3, C and D), and persisted throughout the follow-up, beyond the acute-to-chronic stage of infection (Figure 3, C and D), when immune activation is usually controlled in natural hosts of SIVs (36–38), as seen in controls (Figure 3).