Tc17 cells are induced and recalled in the absence of CD4⁺ T cells.

<p>Mice were vaccinated as described in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1002771#s4" target="_blank">Methods</a>. CD4⁺ T cells were depleted using GK1.5 mAb i.v. weekly throughout the experiment. <b>A.</b> Percent CD8⁺ T cells producing IL-17 in draining LNs (dLNs) and spleen at 19 days post-vaccination in the presence (left panels) or absence (right) of CD4⁺ T cells as assessed by flow cytometry. <b>B.</b> In the left two panels, OT-I T cells (1×10⁶) were transferred to naïve congenic CD4<i>^−/−</i> mice and vaccinated with recombinant <i>Blastomyces</i> expressing the OT-I epitope SIINFEKL. At day 14, dLNs and spleens were harvested and stimulated <i>ex vivo</i> with OVA peptide. In the right three panels, dLNs were harvested and cultured with BMDCs in the presence or absence of heat-killed yeast. Yeast-specific OT-I and endogenous Tc17 cells were enumerated by flow cytometry. The percent (<b>C</b>) or number (<b>D</b>) of polyclonal and yeast-specific Tc17 cells during recall response in the lung 3–4 days after pulmonary infection with wild type virulent <i>Blastomyces</i>. Values are mean ± SD of 4 mice/group. * p<0.05 vs. unvaccinated mice; and ^† p<0.05 vs. vaccinated CD4⁺ T-cell sufficient mice.