Cross-sectional analysis of plasma IL-7 levels in rhesus macaques. Plasma IL-7 levels are depicted for 12 uninfected (▪), 6 SIVsmE660-infected asymptomatic at the time of sampling (♦), and 4 SIVmac239-infected rhesus macaques which progress to simian AIDS and death (•). The minimum detectable level of IL-7 was 0.10 pg/mL.