B6.lpr DN T cell IFNγR expression is critical for their regulatory function. A.

<p>In varying ratios, B6.<i>lpr</i>.IFNγR^−/− or B6.<i>lpr</i>.IFNγR^+/+ DN T cells were cultured with CFSE-labelled B6. Thy1.1.IFNγR^−/− CD4⁺ T cells and irradiated CB6F1.IFNγR^−/− splenocytes and IL-2 for 5 days. Suppression of Thy1.1 CD4⁺ T cell proliferation by B6.<i>lpr</i>.IFNγR^−/− or B6.<i>lpr</i>.IFNγR^+/+ DN T cells was determined by flow cytometry. Data from 6 independent experiments are shown; two-way ANOVA p = 0.004. <b>B.</b> Lethally irradiated CB6F1 mice were reconstituted with BM only (n = 30), BM+CD4⁺ (n = 44), or BM+CD4⁺ plus B6.<i>lpr</i> DN (n = 34), B6.<i>lpr</i>.IFNγ^−/− DN (n = 15), or B6.<i>lpr</i>.IFNγR^−/− DN (n = 13). Recipients were monitored for clinical score and survival as in Fig. 1. Data from Fig. 1B (5 experiments) are included plus 4 additional independent experiments, each with 2–6 mice per group. In comparison with BM+CD4⁺+B6.<i>lpr</i> DN: *log rank p = 0.016 (B6.<i>lpr</i> IFNγ^−/− DN); ***log rank p<0.0001 (B6.<i>lpr</i>.IFNγR^−/− DN); ***log rank p<0.0001 (BM+CD4⁺). <b>C.</b> Representative IFNγ histograms, gated on DN T cells, from one of 6 recipients of BM+CD4⁺+B6.<i>lpr</i>.IFNγR^+/+ DN (solid line) and one of 5 recipients of BM+CD4⁺+B6.<i>lpr</i>.IFNγR^−/− DN are compared with fluorescence-minus-one control (shaded). <b>D.</b> Compiled data from all 11 mice in C are shown. Horizontal lines represent mean MFI; t test p = 0.043. <b>E.</b> Two weeks after BMT, a lower number of Thy1.1⁺ cells were recovered from the spleens of mice treated with BM+CD4⁺+B6.<i>lpr</i> DN T cells as compared with BM+CD4⁺+B6.<i>lpr</i>.IFNγR^−/− DN T cells. Data from 17 recipients of BM+CD4⁺+B6.<i>lpr</i>.IFNγR^+/+ DN T cells and 12 recipients of BM+CD4⁺+B6.<i>lpr</i>.IFNγR^−/− DN T cells pooled from three independent experiments are shown.