Fig. 5.

Individuals with larger Th17 populations displayed reduced T cell activation and superior antiviral immune responses. (A) Bacterial 16S rDNA levels in plasma, assessed by real-time PCR, are correlated with the log Th17:Treg ratio at 8 weeks after infection. (B) Expression of Ki-67 in CD8⁺ T cells indicates a trend to lower T cell proliferation six months after infection, but no statistically significant difference between high Th17:Treg ratio and low Th17:Treg ratio groups. Data are mean +/− SE. (C) Animals with high Th17:Treg ratios before infection have reduced T cell activation in lymph node tissue. The p value shown indicates a significant difference between high- and low-Th17 groups at the 24-week timepoint, calculated using the Mann-Whitney U test. Data are mean +/− SE. (D) More virus-specific T cells develop in animals with more abundant Th17 cells after infection. Virus-specific T cells were measured by intracellular cytokine flow cytometry after stimulation with AT2-inactivated SIV virus. At 8 weeks after infection, animals demonstrating higher Th17 cells also demonstrated more robust antiviral T cell responses. (E) Virus-specific CD4⁺ T cells in high-Th17 animals are more highly functional (i.e., secrete a greater number of different cytokines) and secrete more IL-2 than CD4⁺ T cells in low-Th17 animals. The p value shown was calculated using a Student’s t test and a partial permutation test as described (40).