T cell priming is inhibited in the presence of enhanced STING activation.

<p>B6 mice were immunized with either 10³ CFU ActA⁻Lm-OVA (Δ<i>actA</i>) (open circles), Δ<i>actA</i> in the presence of 50 µg c-di-AMP or <i>tetR</i>ActA⁻Lm-OVA (<i>tetR</i>Δ<i>actA</i>) (open triangles). Naive controls were administered sterile PBS (closed circles). Splenocytes were isolated 7 days post immunization and stained with anti-mouse CD8, CD44, CD62L and K^b/OVA_257–264 tetramer and analyzed by flow cytometry. <b>A</b>. Quantitative analysis shows the total number of K^b/OVA_257–264 tetramer⁺ CD44⁺ CD8⁺ T cells/spleen. <b>B</b>. Histograms represent mice administered PBS (shaded), Δ<i>actA</i> (solid line) or Δ<i>actA</i> in the presence of c-di-AMP or <i>tetR</i>Δ<i>actA</i> (dotted line). Quantitative analysis shows the percentage of CD62L high-expressing cells of the CD8⁺ CD44⁺ K^b/OVA_257–264 tetramer⁺ population. <b>C</b>. Splenocytes were either unstimulated (un) or stimulated with OVA_257–264 (OVA) or LLO_190–201 (LLO) peptides followed by intracellular staining for anti-mouse IFN-γ, TNF-α and IL-2. Quantitative analysis shows the percentage of IFN-γ⁺/TNF-α⁺/IL-2⁻ (solid bars) or IFN-γ⁺/TNF-α⁺/IL-2⁺ (lined bars) within the CD8⁺ or CD4⁺ population. Data are presented as the cumulative results from 2–3 independent experiments (ns = not significant, *p<0.05, **p<0.005, ***p<0.0005).