Phenotype of IL-21–producing cells in SIV-uninfected nonhuman primates. Characterization of IL-21–producing cells in the PB of SIV-uninfected RMs and SMs. (A) The large majority of CD4⁺IL-21⁺ T cells are not Th17 cells. Dot plot shows IL-21 by IL-17 staining in CD4⁺ T cells from a representative RM. The graph shows the fractions of total CD4⁺IL-21⁺ that are IL-17⁺ in PB of all RMs and SMs. (B) Fraction of IL-21⁻IL-17⁺, IL-21⁺IL-17⁻, or IL-21⁺IL-17⁺ CD4⁺ T cells expressing the chemokine receptors CCR6 and α4β7. Dot plots show CCR6 by integrin β7 staining in the 3 populations from a representative RM. The graph shows the percentages of IL-21⁻IL-17⁺, IL-21⁺IL-17⁻, or IL-21⁺IL-17⁺ CD4⁺ T cells expressing CCR6 and/or β7 in all RMs.