Type I IFN-mediated immune suppression is T cell extrinsic.

<p><b>A</b>. B6, <i>IFNAR1^−/−</i> and <i>Gt</i> mice were injected with 1∶1 ratio WT <i>GFP⁺ Ly5.2⁺</i> and <i>IFNAR1^−/− Ly5.1⁺</i> OT-I cells 1 day prior to immunization with ActA⁻Lm-OVA (Δ<i>actA</i>) in the presence (open triangles) or absence (open circles) of 50 µg c-di-AMP or administered PBS (closed circles). Splenocytes were isolated 7 days later and stained with anti-mouse CD8 and CD45.1 and analyzed by flow cytometry. Values in representative FACs plots show the median percentage of WT or <i>IFNAR1^−/−</i> OT-I cells ± SEM within the CD8⁺ T cell population. <b>B</b>. Quantitative analysis shows the percentage (left panels) within the CD8⁺ T cell population or the total number of CD8⁺ T cells/spleen (right panels) of WT OT-I T cells (top panels) and <i>IFNAR1^−/−</i> OT-I T cells (bottom panels). Data are presented as the cumulative results from 2 of 3 independent experiments (ns = not significant, *p<0.05, **p<0.005, ***p<0.0005).