Levels of blood and intestinal IL-21–producing cells in SIV-uninfected nonhuman primates. The percentages of CD4⁺ (●) or CD8⁺ () T cells producing IL-21 but not IL-17 (IL-21⁺IL-17⁻) or both cytokines (IL-21⁺IL-17⁺) after in vitro stimulation were quantified in PB (A) and RB (B) of healthy, SIV-uninfected RMs (left panels) and SMs (right panels). (C) The percentages of CD4⁺IL-21⁺IL-17⁻ (left panel) and CD4⁺IL-21⁺IL-17⁺ (right panel) T cells in PB were compared with those in RB in healthy, SIV-uninfected RMs. Statistical analyses were performed to compare the fraction of IL-21⁺IL-17⁻ or IL-21⁺IL-17⁺ between CD4⁺ and CD8⁺ T cells inside each species (A-B) and to correlate the percentages of CD4⁺IL-21⁺IL-17⁻ or CD4⁺IL-21⁺IL-17⁺ between PB and RB (C).